about the conference - riverflow 2018 · 2018-08-31 · about the conference since 2002, river flow...

About the conference

Since 2002, River Flow has become a major international conference in river engineering andfluvial hydraulics. It is a unique occasion to present and discuss the latest scientific researches,and to communicate with scientists, engineers, and researchers involved in areas such as riverhydraulics and sediment transport. River Flow 2018 focuses on the latest findings in the field offluvial hydrodynamics, addressing fundamental issues related to fluid mechanics and transport ofsediments and pollutants in rivers, and also more practical issues related to river morphodynam-ics at the reach scale: river restoration, the effect of hydraulic structures on bed morphology,flow regime and ecology, and finally to the specific hydraulic processes during extreme floodevents.Five Master Classes dedicated to graduate students and young researchers are organized andled by recognized international experts on topics in hydrodynamics, morphology and sedimenttransport.Exhibitors such as IAHR and Nortek will be present during the three days of the conference. Theconference is coorganized by the National Research Institute of Science and Technology for En-vironment and Agriculture (Irstea), INSA Lyon, Laboratory of Fluid Mechanics and Acoustics(LMFA), Compagnie Nationale du Rhone (CNR) and Societe Hydro-technique de France (SHF).The conference is sponsored by Lyon Metropole, International Association for Hydro-EnvironmentEngineering and Research (IAHR), Auvergne-Rhone-Alpes Region, Lyon University (IDEXLyonproject in the frame of PIA).

Committees

Local Organizing Committee

Chair: Andre Paquier (Irstea)Co-Chairs: Nicolas Riviere (INSA Lyon, LMFA) and Ahmed Khaladi (CNR)Members:

Celine Berni, Irstea Benoıt Camenen, IrsteaAnna Dupont, SHF Jean-Baptiste Faure, IrsteaJerome Le Coz, Irstea Diego Lopez, INSA-Lyon, LMFAEmmanuel Mignot, INSA-Lyon, LMFA Lionel Penard, IrsteaSebastien Proust, Irstea Neda Sheibani, SHFDidier Roult, CNR Ivana Vinkovic, LMFA

IAHR Committee on Fluvial Hydraulics

Chairs: J.F. Rodriquez, chair; A. Paquier, vice chair; A. Dittrich, past chairMembers: S. Dey, K. Koll, A. Leopardi, S. M. Hsu, S. Soares-FrazaoCo-opted members: M. Franca, G. Constantinescu, R. Ferreira

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Scientific committee

Aberle J., Bateman A., Biron P., Blanckaert K., Blom A., Bousmar D., Brewis W., Carling P.,Cassan L., Cheng C., Chu V., Constantinescu G., Cooper J., Crosato A., Da Silva A.M., deMulder T., Dewals B., Dey S., Di Cesare G., Dittrich A., Eiff E., El kadi A. K., Escauriaza C.,Falconer R., Ferreira R., Franca M., Friedrich H., Fromant G., Gaskin S., Gems B., Ghoshal K.,Goutal N., Grabowski R., Greco M., Hager W., Haun H., Herrero A., Hoitink T., Holubova K.,Hsu S.M., Hurther D., Jarvela J., Jodeau M., Kawaike K., Koll K., Kondolf M., Lajeunesse E.,Langedoen E., Lanzoni S., Laronne J., Leal J., Leopardi A., Li C.W., Link O., Malavoi J.R.,Martin Vide J.P., Matousek V., Mosselman E., Muste M., Nakagawa H., Nepf H., Nikora V.,Peltier Y., Peteuil C., Piegay H., Popescu I., Pressiat F., Recking A., Rennie C., RodriguezJ., Schleiss A., Smart G., Soares Frazao S., Sumi T., Szupiany R., Topping D., Uijttewaal W.,Weitbrecht V., Wieprecht S., Yokokawa M., Yu G., Zolezzi G.

Organisation

Access

The conference will be held at the conference center Espace Tete d’Or.Address: 103 Boulevard de Stalingrad, 69100 VilleurbanneFrom Part-Dieu station metro line B, stop Charpennes (10 mn walk)

tram line T1 or T4, stop Tonkin (5 mn walk)bus C2 or 70, stop “Parc Tete d’Or – Stalingrad” (3 mn walk)

From city center (Presqu’ile) metro line A, stop Charpennes (10 mn walk)tram lines T1, stop Tonkin (5 mn walk)

Rooms

A map of the conference rooms is presented below. All sessions will be held on the ground floorexcept sessions “Br”, which will be held in the room Bruxelles on the first floor.

- Brasilia/Caracas (BC): keynote lectures and sessions “BC”- Mexico (Me): sessions “Me”- Lima (Li): sessions “Li”- Bruxelles (Br): sessions “Br”- Main hall (rooms Toronto/Washington): poster session “P”

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Program

The general program is presented below. Please refer to the session number in the followingpages. For example, session BC 1 corresponds to session 1 in the room Brasilia/Caracas, sessionBr 9 corresponds to session 9 in the room Bruxelles.

Tue. 4 Sept. Wed. 5 Sept. Thu. 6 Sept. Fri. 7 Sept. Sat. 8 Sept.

Master class

Opening Keynote Keynote

Technical tour

ceremony lecture lectureKeynote Parallel Parallellecture sessions 3 sessions 7Break Break BreakParallel Parallel Parallelsessions 1 sessions 4 sessions 8Lunch Lunch LunchParallel Parallel Parallelsessions 2 sessions 5 sessions 9Brek Break Break

Poster sessionParallel Closingsessions 6 ceremony

Welcomereception

Master class Conferencedinner dinner

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Conference Themes

A/ River morphodynamics and restoration:- From braiding to meandering rivers- Large river bedforms- Steep rivers, systems of step-pools- Interactions between flow, sediment

and vegetation- River management and ecology, river

restoration

B/ Hydraulic structures and their effects onbed, flow regime and ecology:

- Scour around structures, impact onecology

- Bank erosion and protection- Dams and rivers- Fishways- Inland navigation

C/ Sediment and pollutant dynamics inrivers:

- Sediment supply and management atcatchment scale

- Fine sediment and associated pollutantdynamics

- Impact of bedforms on the flow and par-ticle suspension

- In-situ measurements and modelling ofthe sand dynamics

- Bedload dynamics of a sediment mix-ture

D/ Fluid mechanics and sediment processes:- Mixing processes- Laboratory experiments and innovative

measurement methods- Mechanics of sediment transport- Advanced computational methods for

fluid mechanics,- Sediment transport, and morphody-

namics- Physical models

E/ Extreme events:- Flooding processes and compound

channels- Management of hydrological extremes:

floods and droughts- Urban flooding- Innovative in-situ measurements of the

flow discharge- Computational methods and code cali-

bration for rare events

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Table of contents

Keynote lectures 1

Interactions between flow and vegetation; E. Penning . . . . . . . . . . . . . . . . 2

The challenge of restoring dynamics by river engineering; A. Schleiss . . . . . . . 5

The Rhone River, France; H. Piegay . . . . . . . . . . . . . . . . . . . . . . . . . 8

Wednesday 5 September, 10:45 – 12:45 11

BC 1 – Hydrodynamics within vegetation . . . . . . . . . . . . . . . . . . . . . . 12

Me 1 – Scour around structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Li 1 – Computational methods and code calibration . . . . . . . . . . . . . . . . 25

Br 1 – Sediment case studies (modelling) . . . . . . . . . . . . . . . . . . . . . . . 33

Wednesday 5 September, 14:10 – 16:10 39

BC 2 – Vegetation and sediment transport . . . . . . . . . . . . . . . . . . . . . . 40

Me 2 – Suspended sediment fluxes . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Li 2 – Sediment modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Br 2 – Fishways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Thursday 6 September, 8:45 – 10:25 65

BC 3 – Physical Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Me 3 – Driftwood – part 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Li 3 – Sediments: large-scale/field studies . . . . . . . . . . . . . . . . . . . . . . 78

Br 3 – Flooding processes and compound channels . . . . . . . . . . . . . . . . . 83


BC 4 – Experimental hydrodynamics – part 1 . . . . . . . . . . . . . . . . . . . . 90

Me 4 – Driftwood – part 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Li 4 – Bedform and sediment transport . . . . . . . . . . . . . . . . . . . . . . . 102

Br 4 – Management of hydrological extremes . . . . . . . . . . . . . . . . . . . . 107


BC 5 – Experimental hydrodynamics – part 2 . . . . . . . . . . . . . . . . . . . . 114

Me 5 – Dams and reservoirs – part 1 . . . . . . . . . . . . . . . . . . . . . . . . . 119

Li 5 – Bedload measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

Br 5 – Urban floods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

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BC 6 – Computational hydrodynamics . . . . . . . . . . . . . . . . . . . . . . . . 138

Me 6 – Dams and reservoirs – part 2 . . . . . . . . . . . . . . . . . . . . . . . . . 143

Li 6 – Field measurements of sediment transport . . . . . . . . . . . . . . . . . . 148

Br 6 – Urban porosity models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

Friday 7 September, 8:45 – 10:25 159

BC 7 – Turbulent structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

Me 7 – Ecological survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

Li 7 – Sediments: laboratory experiments . . . . . . . . . . . . . . . . . . . . . . 170

Br 7 – River Experiment Center of Andong, Korea . . . . . . . . . . . . . . . . . 175


BC 8 – Mixing processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

Me 8 – River management and restoration . . . . . . . . . . . . . . . . . . . . . . 187

Li 8 – Investigating bedload processes . . . . . . . . . . . . . . . . . . . . . . . . 193

Br 8 – Innovative in-situ measurements (discharge) – part 1 . . . . . . . . . . . . 198


BC 9 – Flow resistance over rough bed . . . . . . . . . . . . . . . . . . . . . . . . 204

Me 9 – Bank erosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

Li 9 – Bedload and bed evolution modelling . . . . . . . . . . . . . . . . . . . . . 214

Br 9 – Innovative in-situ measurements (discharge) – part 2 . . . . . . . . . . . . 221

Posters 227

P.A – River morphodynamics and restoration . . . . . . . . . . . . . . . . . . . . 228

P.B – Hydraulic structures and their effects on bed, flow regime and ecology . . . 246

P.C – Sediment and pollutant dynamics in rivers . . . . . . . . . . . . . . . . . . 262

P.D – Fluid Mechanics and sediment processes . . . . . . . . . . . . . . . . . . . 266

P.E – Extreme events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

Author Index 296

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Keynote Lectures

Keynote lectures

Room: Brasilia/Caracas

Interactions between flow and vegetation; E. Penning . . . . . . . . . 2

The challenge of restoring dynamics by river engineering; A. Schleiss 5

The Rhone River, France; H. Piegay . . . . . . . . . . . . . . . . . . . . 8

1

Wednesday 5 September, 9:30 – 10:15 Keynote lecture: E. Penning

Interactions between flow and vegetation: translatingknowledge from academic research to daily water management

Ellis Penning ∗ 1

1 Deltares, Ecosystems and Water Quality, p.o.box 177, 2600 MH, Delft, The Netherlands

1. Translating academic research to river management

Over thousands of years people have tried to manage rivers and streams to make most ben-efit out of their functions. A lot of this was initially based on trial and error, and long timeexperience, but over time the built up of expertise, and the development of organized researchon hydrodynamics, morphodynamics and vegetation development became a strong fundamentfor the current understanding of rivers and their behaviour, which allows us to better manageour river systems. Nowadays, highly detailed indoor flume studies on the 3D hydrodynamicprocesses in vegetated flows are being carried out [e.g. 1,2] and used for validating detailed ana-lytical and numerical models of these intricate processes [3]. Most indoor flume studies still useartificial representatives of plants [4], making the comparison with a real field situation challeng-ing [5]. Also, the highly computational intensive numerical models tend to be time consuming,making them less suitable for day to day management. Still, the value of these experimentsand models in management is strong, as based on these detailed measurements and calculationssimplified models have been made that are more adept to daily river management [6,7].During this key-note lecture I will address the potential impact of academic research on watermanagement and how such impact can be made to last. It requires a multidisciplinary dialogto come to integrated water management plans that take into account the requirements of bothflood risk management and ecological restoration for example. In this, the recent developmentsof Nature Based Solutions, also known as Building with Nature solutions, have helped strength-ening this dialog, as natural processes are taken into account to come up with new strategiesfor river management.At the same time there are still many challenges in implementing nature based solutions, espe-cially since many of these new approaches have not yet been put to the extreme tests that areneeded to fully understand their functioning under such rare, yet crucial conditions. Also, thenatural dynamics of vegetation over time can be deemed unpredictable, or undesirable, espe-cially in the longer term, making a good life cycle costing or long term prediction adherentlycomplicated. It is especially in these uncertainties where academic research is needed to helpovercome these obstacles in the implementation of nature based solutions for river management,as they might give solutions on how to take into account these dynamics of the system overtime.

2. Daily practise - quantifying the impact of vegetation on flood risk

Vegetation is a dynamic aspect of rivers, streams and channels that must be accounted forin the management of these water systems. Both riverine floodplain development and instreamvegetation in waterways can cause obstruction during high discharges to the level it can causerisk of flooding. At the same time vegetation in front of dikes may reduce wave impact onthe dikes providing a natural barrier against flooding [8]. Water management must thereforemanage vegetation seasonally or annually (e.g. mowing or grazing).Also today, decisions on how best to manage this vegetation is often done based on expertjudgement or in data-poor situations by the people working directly in the field, despite strongdetailed academic knowledge on vegetated flows is existing. Applying this knowledge can help

∗Corresponding author: [email protected]

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mailto:[email protected]


water managers to make more cost-effective choices in their management. However, it takeseffort to translate this knowledge in meaningful manner for daily practise, taking into accountsome specific requirements to make the knowledge last. Information on the vegetation and itsimpact on hydrodynamic processes must be:1. quickly and easily obtainable and accessible in case immediate action is required;2. reliable and undebatable in case legal requirements need to be checked;3. trustworthy in case a new solution is presented.During this keynote, I will discuss how these three requirements were dealt with in three differentexamples where vegetation-flow interactions were an aspect of the management challenge andhow innovative monitoring techniques and new quantifying tools can help address the challenge.Example one deals with the challenges of mowing instream vegetation in smaller channels duringthe growing season. In these channels little information is available on the exact location ofvegetation blocking the channels and often too much vegetation is mown, harming the ecologicalvalues within the channel. Using hyperspectral camera’s on drones and real time water levelrecordings at gauging stations provide a better spatial and temporal view on the developmentof the vegetation, making it easier to define where and when to mow [9]. These technologicaladvances are new and challenge the traditional ways of working, making a strong dialog withthe end-users necessary from the very start of the development.Example two focusses on assessing floodplain vegetation development in line with the legalrequirements coming from flood risk management within the full area of the river branches ofthe Netherlands. For the full floodplain area a legal map with allowable vegetation types percadastral plot is available (with over 12.000 land owners that need to comply with this legal map)[10]. Before each winter period the current vegetation status in this area must be checked againstthis legal map. Using the latest Sentinel2 satellite images, processed in Google Earth Engineand combined within the legal map in a web-viewer allows to get a first estimate of the areasthat have undergone change compared to the legal map and focus the efforts of maintenance inthese areas in direct discussions with the relevant land owner. In this discussion the accuracy ofthe classification system used to make the comparison with the legal map is still an importantpoint for discussion.Example three focusses on the potential role of vegetation in dike safety under extreme stormconditions. Despite it is well known [e.g 11] that vegetation on foreshores will reduce wave heightand thereby wave run-up and overtopping over dikes, this is not yet quantified for dike safetyin a standard manner [12]. Especially woody vegetation and shrubs can have significant wavereducing capacity [13]. One of the main arguments for not yet including vegetation in dike safetysolutions is the fact that numerical models that can include vegetation in the hydrodynamiccalculations have not yet been validated for these extreme conditions. With vegetation beingdynamic and potentially prone to quick damage during such an event or unforeseen failure duringa normal year (e.g. due to disease) there is a general reluctance against including vegetation indike safety calculations. Both dialog with stakeholders to find solutions for such problems [14]and the use of large scale physical flume facilities is helping bridging this gap by putting realvegetation to the test under extreme conditions in real time, real scale experiments.

3. Summarizing remarks

Fundamental academic research has strengthened the basic understanding of vegetated flows,although we are still lacking a proper understanding of the behaviour of this vegetation underextreme field conditions based on validation data. Fortunately there are more and more exam-ples in which the biomechanical properties of vegetation are taken into account, by either makingrealistic (scaled) surrogates, or simply by carrying out unscaled tests with real vegetation [e.g.15,16, 17, 18].One important part of bridging the gap between these scientific efforts and daily water man-agement is a strong dialog between the two worlds, to ensure that the research carried out ismeaningful, and to ensure that water managers take on board as much of the new insights

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as possible in their management. These new insights are not only the academic advances onvegetated flows, but perhaps more importantly also the latest innovative monitoring tools toobtain data in a different way than the traditional manual way of measuring. By now, the useof portable tablets allows for quick processing and visualisation of information directly in thefield. Online, real time and remote sensing tools have opened up a world of information thatwas not so easily available even ten years ago. In this perspective making a lasting impact ofscientific advances lies also in how these new data streams and technologies can be best used totranslate scientific knowledge for the management challenges ahead.The examples mentioned in this paper are resulting from cooperation with water managers fromthe National Water Board and the Water Authorities Aa and Maas and Rivierenland. I wouldlike to specifically acknowledge the input of Gertjan Geerling, Rik Noorlandt, Alfons Smale,Mindert de Vries, Bregje van Wesenbeeck and Koen Berends (Deltares), Rick Kuggeleijn andStanford Wilson (RWS), Rob Fraaije (Aa and Maas) and Johan van der Meulen and Mathijs Bos(Rivierenland). Some of the innovative aspects of these studies were carried out in cooperationwith the team of the River Experiment Center of the Korean Institute of Civil Engineering andBuilding Technology in Andong South Korea (KICT-REC) and partly financed under the Dutchsubsidy programme Topconsortia for Knowledge and Innovation.

References

1. L. Zong, H. Nepf, Geomorphology 116 (2010) 363–372 (2010)2. K. Bal, E. Struyf, H. Vereecken, P. Viaene, L. De Doncker, E. de Deckere, F. Mostaert, P.Meire, Ecol. Eng., 37(3), 529-533. (2011)3. M.J. Baptist, V. Babovic, J. Rodrıguez Uthurburu, M. Keijzer, R.E. Uittenbogaard, A.Mynett, A. Verwey, J.of Hyd. Res., 45(4), 435-450. (2007)4. M.F. Johnson, R.E. Thomas, T.J. Dijsktra, M. Paul, W.E. Penning, S.P. Rice. In: L.E.Frostick, R.E. Thomas, M.F. Johnson,S.P. Price, S.K. McLelland (eds) IAHR Design Manual.23-41 (2014)5. https://cordis.europa.eu/docs/results/261/261520/final1-final-report-hydralab-iv-48-months.pdf6. J.C. Green, River Res. & App.(21) 671-686 (2005)7. V Verschoren. (PhD thesis), University of Antwerp (2017)8. V. Vuik, S.N. Jonkman, B.W. Borsje, T. Suzuki, I. Kratzer, T.J. Bouma, Coastal Eng. 116,42–56.9. W.E. Penning, G.A.P.H. van den Eertwegh. R & D highlights 2016 Deltares, 74-75. (2016)10. https://staticresources.rijkswaterstaat.nl/binaries/Toelichting%20Vegetatielegger tcm174-367383 tcm21-20334.pdf11. F.J. Mendez, I.J. Losada, Coastal Eng. 51(2), 103–118. (2004)12. Levelt O, Penning E, Smale A, Deltares rapport 11200543-003 (2017)13. J.C. Winterwerp, W.G. Borst, M.B.J. de Vries, J. of Coastal Res. 21(2)223-230 (2005)14. J.E. Venema, H. Schelfhout, M.D. Van der Meulen, Deltares report 1206002-000 (2013)15. U. Ji, J. Kang, Y. Ryu, S. H. Jung, W.E. Penning, V. Harezlak, K.D. Berends and C. Jang,IAHR RiverFlow (2016)16. T. Spencer, I. Moller, F. Rupprecht, T.J. Bouma, B.K. van Wesenbeeck, M. Kudella, M.Paul, K. Jensen, G. Wolters, M. Miranda-Lange, S. Schimmels. ESPL (2015)17. J.T. Dijkstra, R.E. Uittenbogaard,Wat. Res. Research, 46(12), 1–14 (2010).18. K Vastila, J Jarvela – Wat. Res. Research 50(1): 229-245 (2014)

Keywords: vegetated flows, water management

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Thursday 6 September, 8:00 – 8:45 Keynote lecture: A. Schleiss

The challenge of restoring dynamics by river engineering: whereto find the truth about river flow - in the computer, in the lab

or in the field?

Anton J. Schleiss ∗ 1

1 Laboratory of Hydraulic Constructions (LCH), Swiss Federal Institute of Technology Lausanne(EPFL) – EPFL ENAC IIC LCH; Station 18; CH-1015 Lausanne, Switzerland

Rivers are probably the most complex features which we can be found in the environment.They have been and are still the driving force for shaping landscapes and biotopes on our planet.The behavior of river systems is a result of the complex interaction between flow, sediments,morphology and habitats.

“Nature is not to be trifled with, she is always true, always earnest, always severe; she isalways right, and the faults and errors are always those of man.” (Goethe)

Hydraulic engineers responsible for the planning of river training and restoration works aswell as scientists doing river research should bear well in mind this quotation from Goethe. Re-liable and sustainable protection against floods can only be assured by hydraulic structures thatpreserve the natural character of a watercourse during flood events which is often difficult toidentify. Accordingly, modern river engineering must take a river’s natural forces and behaviorinto account. For example, attempts to straighten a meander that has developed naturally maybe dangerous: in extreme flood conditions, if not earlier, the apparently tamed river will recalland reoccupy the space to which it is entitled [1].

“The world is like a river, running along in its bed, this way and that, forming sand barsby chance and then being forced by these to take a different course. Whereas this all proceedssmoothly and easily and gradually, the river engineers have great difficulties when they seek tocounteract this natural behavior.” (Goethe)

Goethe (once again) recognized that the dynamics of a river can only be controlled to a lim-ited extent by channel modifications and rigid river training works. The term “dynamics” refersto variations in hydro-morphology over space and time due to flood discharges and sedimenttransport. These processes regularly lead to the destruction of habitats, especially in riparianareas, and the creation of space for new habitats. Dynamic watercourses require a lot of space.For example, naturally meandering rivers may migrate laterally within a belt of roughly 5–6times the width of the channel bed. In the valleys of the Alps and Pre-Alps the rivers originallyrequired the entire valley floor. As well as providing flood protection, watercourse alterationscarried out over the last two centuries were designed to reclaim land for development and agri-culture. Efforts were thus made to impede the dynamics: rivers and streams were channelized,and channel bed widths were optimized with regard to sediment transport. This resulted inmonotonous watercourses, with almost no variation in hydraulic or morphological characteris-tics. The today’s challenge of river engineers in collaboration with environmental scientists isto restore the channelized river under the constraints of high urbanization and limited space.The behavior of river systems is a result of the complex interaction between flow, sediments,


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morphology and habitats. Furthermore, rivers are often also a source for water supply andenergy production as well as a waterway for transportation.

“Water is a friendly element for whoever is familiar with it and knows how to manage it.”(Goethe)

This quotation from Goethe reminds us that structural flood protection measures need to bebased on a detailed knowledge of the processes associated with flooding and of hydro-ecologicalconditions. In this way, interventions can be kept to a minimum. Even so, river dynamics willinevitably be reduced by flood control structures.The aim of rehabilitation measures is to restore watercourse dynamics as far as possible, therebyincreasing structural diversity. This aim is only attainable if the river engineering measuresas river training works are increasing the diversity of flow patterns, which in turn will havefavourable effects on the species diversity in the river. Even unavoidable riprap on an almoststraight stretch of water should be undulated in such a way as to increase flow diversity. Struc-tural richness always depends on a minimum level of river dynamics, leading, for example, toregular rearrangement of sediments in the channel and local bank erosions. In this context offlood protection and river restoration, scientists and design engineers are confronted with thechallenge to select the appropriate research or design tool in order to give the right answers inview of finding the best sustainable solutions for a certain project or scientific question. Thus,the question arises where to find the truth about river flow: in the computer, in the lab orin the field? The challenge described above will be illustrated with three examples of researchand development projects described briefly in the following. The important floods in the years1993 and 2000 revealed a protection deficit along the Gamsa River in its downstream stretchbefore its entry in the Rhone [2] [3]. A critical infrastructure, namely a chemistry factory for theproduction of explosives, was seriously endangered by these floods revealing a damage potentialwith catastrophic consequences. Based on the event analyses and the local conditions a floodprotection project was defined. The river training measures consist of heavy concrete prisms ar-ranged and buried along the river bank as a kind of riprap and groynes. Sediment managementand retention completed the protection concept. The constructive protection measures wereexamined in a large scaled hydraulic model built outdoor closely approximating the behavior ofthe prototype. The interaction of the concrete prisms with the highly turbulent flow combinedwith high concentration of sediment transport as well as need of unsteady event simulation, isclearly beyond the potential of numerical simulations.In rivers, downstream of hydroelectric storage power plants, frequent and intense flow varia-tions occur resulting from peak power production. Subjected to this so-called hydropeakingphenomenon, the fish population suffers from a known decline. In the research of mitigationsolutions, shelters in riverbanks may be a protection measure against excessive flow velocities.Such shelters were studied systematically in an experimental set-up with juvenile brown trout,in a channel equipped with a lateral embayment, and supplied with freshwater [4] [5] [6]. Thepurpose of the experiments was to generate hydrodynamic conditions in the channel that areuncomfortable for fish on one hand and to attract them to the shelter on the other hand. Theflow velocity distribution in the intersection between the main channel and the lateral shelterwas found to be a significant parameter for the fish attractiveness of the shelter. The utiliza-tion rate of fish of the shelter is used as a performance indicator defined as the number of fishpresent in it compared to the total fish number. With a basic rectangular shelter configuration,the utilization rate was only of 35%. Introducing a deviation groyne that enforced a waterexchange between the channel and the shelter could double this rate. The position and theorientation angle of such groyne have been systematically varied with the purpose of maximiz-ing the frequentation rate. Maximum rates approaching 90% could be obtained with the bestconfiguration, composing an island type groyne in the shelter. An approach of hybrid modelling

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was used. First the flow pattern and the hydrodynamic exchange between the main channeland shelter was obtained by numerical simulation for a large number of shelter configurations.Then most promising configurations were tested in a hydraulic model large enough in order toobserve the behavior of juvenile trout as under field conditions.As already mentioned, nowadays flood protection and river engineering projects have to improvealso the ecological condition of the river. Very often the space is not available for a full restorationof the river morphology. Therefore, the hydro-morphological heterogeneity has to be optimizedwithin certain space constraints. For such projects a tool for practitioners is very helpful whichallows to quantify the habitat heterogeneity enhancement for different project alternatives andto recommend the best alternative in view of eco-morphological perspective. For overcoming thischallenge, a new Hydro-Morphological Index of Diversity (HMID) was proposed, which allowsa quantitative statement of the enhancement of habitat heterogeneity during the comparison ofdifferent project alternatives in the framework of river engineering projects [7] [8] [9]. Comparedto other existing habitat indices, which are mostly based on visual, qualitative assessment in thefield and therefore influenced by the subjectivity of the observers, the new HMID is based onstatistical parameter calculated by numerical 2D and 3D simulations during project planningand thus can be denoted as fully objective. The HMID was developed on the basis of very ex-tensive field campaigns by recording a large amount of hydraulic and geomorphic data. In orderto see the hydro-morphological heterogeneity clearly several very contrasting sites from fullynatural to very channelized stretches have been analysed on three different gravel bed rivers inthe Swiss Pre-alps. By comparing the variability of the numerous hydraulic and morphologicalparameters between the studied stretches a formula for the HMID could be proposed. It couldbe shown that for the investigated river types the coefficients of variation of flow velocity andwater depth alone are sufficient to obtain a reliable and predictive HMID.

References

1. A. Schleiss, Eawag News, 61e, 18-20 (2006).2. T. Meile, M. Bodenmann, A. Schleiss, J.-L. Boillat, Int. Symposium Interpraevent Riva delGarda, Band 2, 219-230 (2004).3. T. Meile, A. Schleiss, M. Bodenmann, J.-L. Boillat, M. Jaeggi, Wasser Energie Luft, 97(3/4),59-66 (2005).4. J.-M. Ribi, K. Steffen, J.-L. Boillat, A. Peter, A. J. Schleiss, Proceedings of the 33rd Congressof IAHR, Vancouver, Canada, 9.-14. August 2009, CD-Rom, 6074-6081 (2009)5. J.-M. Ribi, J.-L. Boillat, A.J. Schleiss, River Flow 2010, 8-10 September 2010, Braunschweig,Germany, Ed. Dittrich, Koll, Aeberle & Geisenhainer (eds), Bundesanstalt fur Wasserbau, 665-671 (2010).6. J.-M. Ribi, J.-L. Boillat, A. Peter, A. J. Schleiss., Aquatic Sciences, 76(4), 527-541 (2014).7. W. Gostner, Ch. Baumgartner, T. Staheli, M. Alp, A.J. Schleiss, Ch. T Robinson, Pro-ceedings of the 33rd Congress of IAHR, Vancouver, Canada, 9.-14. August 2009, CD-Rom,6742-6749 (2009).8. W. Gostner, M. Alp, A.J. Schleiss, Ch. T Robinson, Hydrobiologia, 712(1), 43-60 (2013).9. W. Gostner, P. Parasiewicz, A.J. Schleiss, Ecohydrology, 6(4), 652-667 (2013).

Keywords: Restoration, river dynamics, river engineering

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Friday 7 September, 8:00 – 8:45 Keynote lecture: H. Piegay

The Rhone River, France: applying integrative sciences tosustainable management

Herve Piegay ∗ 1

1 Environnement Ville Societe (EVS) – Ecole Normale Superieure - Lyon : UMR5600 – UMR 5600 18Rue Chevreul 69362 Lyon cedex 07, France

1.1. Rhone River issues

The Rhone River is one of the main European alpine rivers (watershed: 98 500 km2; length:812 km total, 560 km in France; mean annual discharge at its mouth: 1700 m3/s; annual flood:4000 m3/s), and the primary freshwater input to the western Mediterranean basin. It was mainlyan upland river transporting gravel up to its delta and continuously supplied in sediments by itsAlpine braided tributaries. The Durance River was one of the most active system before beingcontrolled for producing electricity and supplying water for irrigation. The fluvial landscape hasbeen engineered for more than 150 years, leading to altered aquatic and riparian ecosystems andsocial tensions in terms of local development scenarios. The channel was regulated between 1850and 1930 for navigation purposes (embankments, groynes, dykes), then dammed for producingelectricity (1898-1986: 21 hydroelectric dams, most of them with derivation canals). It is alsoequipped with 4 nuclear powerplants that use the river water for their cooling.After more than a century of developments leading to major biological and physical changes dueto a significant artificialization of the river corridor, problems and stakes are still existing in termsof human safety, user satisfaction and local development and the aim is now to improve existingconditions and promote a sustainable development, shared by all actors. Today, stakeholdersface tension in balancing various user interests regarding nature conservation, flood control,economic and recreational activities, ecological improvement. The French Rhone stakeholdershave beencommitted since 2003 in implementing a large inter-regional sustainable developmentmasterplan funded by the European Union (ERDF) called Plan Rhone I and II, focused on thewhole river corridor. They created a collective framework grouping local actors to go beyondthe complex and sometimes contradictory logics of each of them.

1.2. Interdisciplinary scientific initiatives

In this context of active public debate at a large continuum scale, scientists are engagedto provide knowledge to feed discussions and help decision-makers. Scientists have been struc-tured since 2002 within a Rhone basin scientific consortium (ZABR – ILTER site), which isinterdisciplinary and supported by a set of academic institutions from Aix-Marseille and Lyon,as well as Besancon, Nımes, Montpellier, Grenoble and Chambery. The ZABR community isorganised in Observatories and Research sites to cover the different environmental issues existingthroughout the catchment. The Rhone River corridor is one of these Research sites, organisedsince 2010 as a human-environment observatory, labelled at a national level by CNRS (NationalScientific Research Center). The Rhone River corridor has thus become an experimental field, acollaborative and integrative science platform, for integrated sciences in terms of partnerships,scientific practices and interdisciplinarity to produce new knowledge and innovate, to informriver managers and citizens, and to help environmental policy implementation. The objectiveof the “Rhone Valley” Human-Environment Observatory is to provide and share knowledge forimproving river management practices, considering simultaneously public policies, human atti-tudes, biophysical and chemical dynamics. The observatory is based on a co-construction processof research actions between scientists and stakeholders focused on major practical issues such


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as the transfer of sediment and associated pollutants, the river-sea interactions, the definitionof the good ecological potential, the ecological restoration of the river, the program of channelwidening, or even the social framework of the Rhone River.

1.3. An observatory of the sediments

In this context, an observatory of the Rhone sediments (OSR) was created in 2008, in-volving an interdisciplinary research team (hydrology, hydraulics, geomorphology, geochemistry,ecotoxicology, geomatics, sedimentology) in strong interactions with river practitioners. Theaim of this research group is to provide new scientific knowledge over the Rhone River fromLake Geneva to the Sea for promoting a sustainable management of channel forms and sedimentprocesses. A set of key-questions was asked by stakeholders, which needs several years to beanswered: How has the geometry of the channel evolved over the last two centuries? What is theimpact of the river geometry and existing infrastructures on the flooding risk or the ecologicalpotential of the river? What is the annual bedload transport? What is the contribution ofsediment delivery to the beach evolution of the delta and Languedoc coast? What is the impactof development and management activities such as dredging, channel maintenance or sedimentflushing from dam reservoirs? What suspended sediment and contaminant fluxes are transferredto the Mediterranean Sea? Where do they come from and what are their temporal patterns?Are they stored all along the river reach and do they affect the geometry of the bed? Can wepredict the sediment transfer and deposition? How can we store and share data between scien-tists and practitioners for feeding the public debate? Major advances have been done to bettercharacterize and explain the channel evolution of the last century, highlight aquatic and riparianhabitat conditions, and assess channel sensitivity to climate and land-use changes. A networkof monitoring stations is now operating so that fluxes of suspended sediments and associatedcontaminants (metal content, organic pollutants and radionuclides) are continuously monitored.An annual quantification of sediment budget has been done and some events such as the floodsof May-June 2008 and May 2015 or the sediment flushing operations of June 2012 and June2016 were also monitored at the scale of the 512 km river length. Tools and protocols developedfor monitoring sediment transfers, archiving data and informing practitioners will be introducedin this keynote lecture.

1.4. An ecological restoration program

Hydraulic engineers, ecologists, geomorphologists and social scientists are also strongly in-volved since the 1990’s in restoration programs, especially through their monitoring for evalu-ating the success of this policy. An ambitious program of ecological restoration of the RhoneRiver began at the end of the 90’s with eight priority reaches. This program was focused onthree thematic axes, namely the restoration of migration routes for fish, the increase of mini-mum flows in sections by-passed by hydroelectric canals, and the rewatering and reconnectionof remnant former channels. The Pierre-Benite site downstream of Lyon was restored between1999 and 2000. Three sites in the Upper Rhone River (Chautagne, Belley and Bregnier-Cordon)were then restored between 2004 and 2006. The program is now implemented downstream ofLyon, in the by-passed reaches of Peage-de-Roussillon, Donzere and Montelimar. Scientistshave monitored the effects of restoration measures on the physical and biological components(aquatic vegetation, benthic invertebrates and fish). The results, fairly unique over such a longperiod of time demonstrate minimum flow increase and habitat diversification have significantpositive effects on fish and invertebrate communities. Physical monitoring also confirms thatsuch restoration of channel forms is fairly sustained in the Rhone context. Monitoring effortshave been combined with modelling so that practical tools exist to predict a priori what canbe potentially the ecological and geomorphic responses of target actions. These tools are usedfor implementing new restoration actions and recent efforts have been paid to test these toolson other river systems. The restoration policy has also evolved through time and process-based

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restoration is more and more promoted. Tests and pre-project appraisals are done for aug-menting gravel transport and re-eroding banks following groyne fields removal. This researchis based on hydraulic modelling combined with intensive geomorphic field surveys (DEM, grainsize, particle tracking). Potential benefits and risks linked to promoting gravel augmentationand removing groyne fields are assessed in a restoration context. Dismantling some of the groynefields has strong potential to provide multiple benefits. It is recommended that managing guide-lines should be adapted according to local conditions, as well as expected benefits and needs,and conducted in co-ordination with all actors involved in and affected by the restoration.

Web sites

1. Plan Rhone : http://www.planrhone.fr/front/index.php2. Rhone basin scientific consortium (Zone Atelier Bassin du Rhone) :http://www.graie.org/zabr/index.htm3. Rhone Valley Human – Environment Observatory (Observatoire Homme – Milieux Vallee duRhone) : http://ohm-vr.org/4. Observatory of the Rhone sediments (Observatoire des sediments du Rhone) :http://www.graie.org/osr/5. Program of ecological restoration of the Rhone River (Suivi scientifique du ProgrammeDecennal de Restauration) :http://restaurationrhone.univlyon1.fr/index.php?action=restauration& do=presentation

Keywords: Sustanaible management

10

Wednesday 5 September, 10:45 – 12:45

Wednesday 5 September

10:45 – 12:45

BC 1 – Hydrodynamics within vegetation . . . . . . . . . . . . . . . . . 12

Me 1 – Scour around structures . . . . . . . . . . . . . . . . . . . . . . . 19

Li 1 – Computational methods and code calibration . . . . . . . . . . 25

Br 1 – Sediment case studies (modelling) . . . . . . . . . . . . . . . . . 33

11

Wednesday 5 September, 10:45 – 12:45 BC 1 – Hydrodynamics within vegetation

Drag and Reynolds stress distribution within submergedvegetation canopies

Nina Nikora ∗† 1, Vladimir Nikora 1

1 University of Aberdeen, School of Engineering – United Kingdom

In the last few decades extensive studies focusing on both qualitative and quantitative de-scriptions of the Reynolds stress within aquatic canopies have been carried out. Although thesestudies have advanced our knowledge of mechanics of flow-vegetation interactions, further re-search in this area is still required. In particular, there is a need for development of new simplephysically-based relationships describing the Reynolds stress profiles within submerged vegeta-tion canopies. This paper addresses this issue and proposes a physically justified formulationfor the Reynolds stress profile within the canopy region.

Keywords: Vegetated flow, Reynolds stress, drag, open, channel flow, momentum transfer

∗Speaker†Corresponding author: [email protected]

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LES modelling of a flow within an infinite array of randomlyplaced cylinders: Anisotropy characterization

Ana M. Ricardo ∗† 1, Dimokratis Grigoriadis 2, Rui Ferreira 1

1 CERIS, Instituto Superior Tecnico, Universidade de Lisboa, Portugal (CERIS - IST) – Av. RoviscoPais 1, 1049-001 Lisbon, Portugal

2 UCY-CompSci, Department of Mechanical and Manufacturing Engineering, University of Cyprus(UCY- ComSci) – 75 Kallipoleos Avenue, P.O.Box 20537, Nicosia, 1678, Cyprus, Cyprus

The LES approach is employed to model flows within random arrays of emergent cylinders.The model is validated against laboratory data acquired with a 2D-2C Particle Image Velocime-try system. The main goals are: i) discussion of the effect of the numerical domain size andthe grid resolution on the predicted flow variables; and ii) spatial characterization of the flowanisotropy. Three domains of different sizes (16 to 36 cylinders) and four grid resolutions wereindependently tested. A 2D methodology was proposed to characterize the flow anisotropy onthe horizontal plane. The results show that the first and second order moments were not sig-nificantly affected by the size of the tested numerical domains or by the grid resolution. Thecomparison with laboratory data showed a fair agreement confirming that the numerical modelwas able to adequately reproduce all the components of the Reynolds stress tensor. The resultsshow that turbulence is of axisymmetric expansion nature in this type offlow. Relatively to the degree of anisotropy, the highest values were found close to the cylin-der, decreasing gradually downstream towards the isotropy state. However, a truly isotropicturbulence state is not reached.

Keywords: Infinite array, random distribution, LES, domain size, wake controlled stratum, anisotropy,

Lumley plots


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Cycloid flows induced by the large horizontal coherentstructures in the vegetated compound channel.

Son Truong-Hong ∗† 1,2, Wim Uijttewaal 1

1 Delft University of Technology (TU Delft) – Building 23, Stevinweg 1, 2628 CN, Delft, Netherlands2 Thuy Loi University, Hanoi, Vietnam – Vietnam

Vegetation in general and mangrove, in particular, plays a significant role in the protectionof the coastal and estuarine regions from erosion. In particular, estuarine mangrove forestscan efficiently reduce the impact of a strong along-bank flow during high tides and high riverdischarge, creating shelter regions for the development of the ecological system. As estuarinemangrove is usually inundated during high tides and exposed to strong tidal flows, the hydro-dynamic of estuarine mangrove forest is similar to that of a vegetated compound channel. Inorder to gain more insight into this field of the research, a hydraulic laboratory experiment of ashallow flow field in a vegetated compound channel has been conducted. Experimental resultsconfirm a pronounced existence of large horizontal coherent structures (LHCSs). Although thepresence of the large horizontal coherent structures in the vegetated channel has been well rec-ognized, it is still unclear how they affect the flow field, mass and momentum exchange in thevegetated compound channel. Detailed analyses of the experimental data reveal more aboutthe role of the large horizontal coherent structures. The flow field under the effect of the largecoherent structures shows a spatially and temporally cycloid motion, contributing a large partto the momentum and mass transfer. The quadrant analysis of the Reynolds shear stresses hasbeen applied to examine the connection between the motion of the large horizontal coherentstructures and their associated cycloid flow events.

Keywords: large coherent structures, compound channels, vegetation.


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Flow structures in a shallow channel with lateral bed-roughnessvariation

Yulia Akutina ∗† 1, Maxime Rouzes 2, Frederic Moulin 2, Olivier Eiff 1

1 Institute for Hydromechanics, Karlsruhe Institute of Technology (KIT) – Germany2 Institut de mecanique des fluides de Toulouse (IMFT) – Universite de Toulouse Paul Sabatier – France

Highly heterogeneous floodplains can give rise to secondary flow structures responsible forthe bulk of lateral momentum exchange. Quantifying the redistribution of momentum is re-quired to predict lateral profiles of flow velocity and the associated water level in a river. In thework herein, we focus on studying secondary flow structures and the momentum redistributionassociated with a lateral bed-roughness variation in a channel with low relative submergence ofthe roughness elements, h/k = 3, 2 and 1.5, where h is the flow depth and k is the roughnessheight. A series of laboratory experiments were performed in a flume containing rows of cubes.They were arranged in two types of regular patterns, with higher and lower frontal density, andplaced side by side such that the bed roughness varies in the lateral direction. The measure-ments were performed using stereoscopic PIV in a vertical cross plane spanning between the tworoughness types. The time-averaged and turbulence statistics of the three components of thevelocity field were analyzed. First, we focus on the intensity of the secondary currents. As theflow becomes shallower (lower relative submergence), the cross-stream velocity normalized bythe streamwise velocity increases. A large-scale secondary current at the border between the tworoughnesses as observed in Vermaas et al. 2011 (though in their case between smooth and roughregions) appears for h/k = 3. As h/k decreases, this structure reaches to the same size as thesecondary flow generated by the roughness elements. Also, the discharge distribution betweenthe two sides of the channel becomes less uniform with decreasing h/k. In this sense, the rel-ative importance of the roughness difference increases with decreasing water depth. Moreover,higher discharge is observed on the side with higher equivalent sand roughness, contrary to whatis observed for smooth-to-rough transition (Vermaas et al. 2011, Dupuis et al. 2018). Timeseries of the streamwise velocity fluctuations are calculated using Taylor’s ”frozen turbulence”hypothesis. In this representation, streamwise velocity streaks are apparent for h/k = 3, butthey appear to lose coherence for the most shallow case of h/k = 1.5.

Keywords: lateral roughness variation, low relative submergence, secondary currents, velocity

streaks, stereoscopic PIV


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Shallow flow over a bed with a lateral change of roughness

Victor Dupuis ∗† 1, Frederic Moulin 1, Sebastien Cazin 1, Moıse Marchal 1, PierreElyakime 1, Jean-Dominique Barron 1, Olivier Eiff 2

1 Institut de Mecanique des Fluides de Toulouse (IMFT)– 2 Allee du Professeur Camille Soula 31400Toulouse – France

2 KIT – Karlsruhe Institut of Technology (KIT) – France

River beds frequently exhibit a lateral variation of roughness. For example, in the case ofan overflowing river, the main channel has a smoother topography compared to the adjacentfloodplains where vegetation and land occupation yield an important hydraulic roughness. Thelateral difference in roughness can induce a high lateral velocity gradient within the river cross-section that gives birth to a mixing layer. This mixing layer leads to fluid and momentumtransfers between the two adjacent beds. To understand such mixing processes in rivers isimportant for predicting stage-discharge relationships and the velocity distribution within thecross-section. In order to address these issues in the context of a shallow water flow with a waterdepth h of the same order as the roughness elements of the bed, experiments were undertakenin a 26 m long and 1.1 m wide glass-walled open-channel flume. One half-side of the bed wascovered with an array of cubes of height k arranged in a square configuration, the other sidewith smooth glass. Three different levels of cube submergence h/k were examined (h/k=0.8,1.5 and 2). The experiments and measurements were designed to yield the flow in the completevolume of the interstices across the cube array. To achieve this, 2C-3D linear-scanning PIVmeasurements with zero-parallax optics were developed and set up. The measurements revealedthe complexity of the flow structure around the interface between the rough and smooth beds.The results show that the ability of the mixing layer to exchange momentum is highly dependenton the level of the cube submergence h/k.

Keywords: open channel turbulence, lateral mixing layer, lateral roughness transition, 2C 3D linear

scanning PIV, low relative submergence, shallow flows


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Near wake of emergent vegetation patches in shallow flow

Sina Wunder ∗† 1, Michele Trevisson 1, Christoph Heckele 1, Loıc Chagot 2, BrendanMurphy 3, Stuart Mclelland 3, Frederic Moulin 2, Olivier Eiff 1

1 Karlsruhe Institute of Technology (KIT) – Germany;2 Institut de mecanique des fluides de Toulouse (IMFT) – France;

3 Hull University – Hull, HU6 7RX, United Kingdom

River floods are expected to become more intense and to occur more frequently due to climatechanges. Yet, our ability to predict the resulting flow velocities and water levels using larger scalenumerical models remains inaccurate due to the difficulty in quantify the flow resistance thatresults from submerged natural and man-made obstacles. Among these obstacles, vegetationpatches are particularly difficult to quantify in terms of flow resistance due to their complexgeometry and topological behaviour under hydrodynamic loading. They not only influence thewater level and mean velocities due to the drag they exert, but they also affect the turbulence andhence all transfer processes such as the sediment transport dynamics in the surrounding area.Their growth is itself determined by the antecedent interactions with local turbulence and bedshear stress within and around the patch. The flow resistance and behaviour of patches dependson the allometric characteristics of the vegetation patch itself. These are generally describedby frontal density, solid volume fraction, leaf area index (LAI), shape and flexibility, but thereare significant uncertainties in these parameters due to flow-dependent variations which requireparameterization for implementation in larger-scale numerical models.Existing studies dealing with the interaction of flow and vegetation concern mostly measurementsof the drag of single plants for both emergent and submerged conditions, followed by analysesof the flow through and above homogeneous canopies, again for both emergent and submergedconditions. However, studies of the flow around single patches are uncommon and are mostlyrestricted to emergent conditions. The effect of submergence on the flow pattern through andaround patches remains largely unexplored. For streamlined leafy plants there is very limitedinformation and understanding of how the flow evolves through and around the plants as well asthe resulting drag for different levels of submergence, even for homogeneous canopy flows. Thiswork aims at filling these gaps via complementary physical lab-scale and numerical experimentsof the flow through and around an artificial and a real vegetation patch. The experimental workis focused on PIV measurements in the wake of the patches whereas the method of large-eddysimulation is employed to provide additional insights of the flow inside the patch.The 6 m wide Total Environment Simulator flume in Hull was used to be able to achievehydraulically relevant allometric parameters of real plants in shallow flow while minimizingside wall effects. Experimentally the mean and turbulent flow in and around a single patchand a real leafy plant in shallow configurations covering emerged and submerged conditionsare investigated to study the effect of the penetrating flow on the momentum exchange of anartificial patch complying with the ratio of porosity to leaf area index (LAI) of a real plant.The patch was a geometrically ordered structure designed with a defined number of verticalthin glass plates in a staggered configuration with geometric similitude to a real leafy plant.The design of the geometry (number of plates per base area) meets the natural values of solidvolume fraction and porosity and the leaf area index of a natural streamlined plant and willreproduce turbulent flow conditions. In order to scale the laboratory dimensions to those of areal leafy plant, a surrogate for natural willows was also used. Measurements were performed bystereoscopic 2D-3C PIV measurements for two relative submergences (hp/h = 1, hp/h = 2/3) inorder to investigate both the effect of the patch on the flow and resulting flow resistance and the


17



changes induced by the flow condition due to submergence. The total resistance of the artificialpatch as well as the natural plant are quantified and compared by measuring the momentum fluxaround the patch and the free-surface height under identical flow conditions. Thus, the studyprovides the necessary data and understanding to extend and improve existing parametrizationsfor the flow through vegetation.

Keywords: 2D3C PIV, vegetation hydraulics, flow resistance, porous media

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Wednesday 5 September, 10:45 – 12:45 Me 1 – Scour around structures

Viscosity effects on local scour around vertical structures inclear-water conditions

Costantino Manes ∗† 1, Francesco Coscarella 2, Ashley Rogers 3, Roberto Gaudio 2

1 Politecnico di Torino – Italy2 Universita della Calabria – Italy

3 University of Southampton – United Kingdom

Local scour represents the erosion process that occurs at the base of hydraulic structuresoverlying sediment beds. Horseshoe vortices forming at the bed-structure junction are the mainresponsible for sediment removal and dictate erosion rates as well as the maximum erosion depthresulting from a significant flow event. In steady-flow conditions this is often referred to asthe equilibrium scour depth, which, for many hydraulic structures, represents a key parameterfor foundation-design and risk-assessment purposes. The equilibrium scour depth has beeninvestigated for decades and many predictive formulae have been developed following the classicalempirical approach, whereby numerous experimental datasets are used to isolate and identify theinfluence of non-dimensional groups emerging from dimensional analysis. Within this context,the influence of obstacle Reynolds numbers, and consequently of viscous forces, has always beenneglected because of the large Re values normally encountered in engineering and laboratoryconditions. The present paper demonstrates that this assumption is largely incorrect especiallyfor beds made of sand or finer material. The theoretical analysis presented in Manes andBrocchini ([1]) is herein extended to include viscosity effects and investigate their importanceon equilibrium scour depths forming around obstacles resembling bridge piers.

Keywords: scour, turbulence


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Similitude of scour around bridge piers

Oscar Link ∗† 1

1 Professor (UdeC) – Prof. O.Link, Faculty of Engineering. University of Concepcion. EdmundoLarenas 215. Barrio Universitario. Concepcion 403000., Chile

Scaled movable bed river models provide valuable information on prototype fluvial processesthat can be difficult to obtain in the field or with mathematical techniques (Gorrick & Rodrıguez2014). Similitude between the prototype and model relies on equating dimensionless parametersfor the flow and sediment transport thus preserving consistent ratios of the dominant forces(Yalin & Kamphuis, 1971). However, maintaining similitude between movable bed laboratorymodels and the larger rivers they represent is difficult to do exactly, and scale effects arise.The estimation of how scale effects qualitatively and quantitatively affect the model results andwhether or not they can be neglected is a challenge for physical modelers (Heller, 2011). Thedesign of scour tests should be improved so that more quantitative results can be obtained frommodel tests (Shen 1990).The bridge pier scour involves complex interactions between the 3D unsteady flow and theriverbed sediment around the pier (Link et al. 2012, Link et al. 2017). Raudkivi (1986) pre-sented the functional trends of scour. Melville and Chiew (1999) studied the temporal scale inbridge pier scour showing that the scour depth after 10% of the time to equilibrium is about 50 -80% of the equilibrium scour depth, depending on flow intensity. Lee and Sturm (2009) showedthat scour strongly depends on the relative size of the pier to sediment, D/d. Using scalingarguments, Cheng et al. (2016) showed that parameters in scour formulas that consider scouras an exponential function of time strongly depend on D/d. Further, Ettema et al. (1998, 2006)analyzed the scale effects on scour concluding that the use of laboratory flumes in developingaccurate predictors of scour depth at full-scale piers is limited due to scale effects that mayproduce greater scour depths Z* at the laboratory than at actual piers in rivers.In this paper, a new set of dimensionless parameters controlling scour is derived following dimen-sional analysis and similitude theory leading to the working hypothesis: If the dimensionless,effective flow work W* by Link et al. (2017) and the dimensionless grain diameter D* are identicin prototype and model, then the obtained scour at a bridge pier is similar.The ability of W* and D* to reproduce scour is tested through experiments conducted in threedifferent flumes having different sizes and piers, with five sediments of different sizes and densi-ties, covering steady and unsteady discharges, as well as clear-water and live-bed conditions.Our results confirm the working hypothesis. Remarkably, is the fact that previously reportedscale effects in models with distorted pier to sediment ratio become negligible if W* and D*are kept similar as in prototype. Especially this result highlights a common missinterpretationof the so-called equilibrium scour, indicating that scour is highly sensitive to the experimentduration even when conditions close to equilibrium are reached. Meanwhile, recommendationson the way we compare scour results are given.

Keywords: Bridge pier scour, similitude theory, physical modelling in loose boundary hydraulics


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Scouring due to submerged sills

Ashley Dudill ∗† 1, Jose Vasquez 2, Dave Mclean 2

1 University of British Columbia – Canada2 Northwest Hydraulic Consultants – Canada

Scour in a river occurs when sediment forming the channel is eroded by the flow withoutcompensating replacement. As the construction of infrastructure in and around a river chan-nel modifies the flow and sediment transport characteristics, prediction of scour depths is anintegral part of engineering design. Accurate estimations of scour depth are essential to en-sure appropriate bed protection is provided to prevent the risk of structural failure. Whilstthere are a substantial number of predictive equations available to estimate the scour resultingfrom bridge piers, other types of structures have been less examined. This paper reports onflume experiments and numerical modelling to examine the role of submerged sill height in thedevelopment of scour. Sills can be utilised in a river to control bed stability, influence mixing dy-namics or dictate water levels. Additionally, sills may be introduced as a result of infrastructuresuch as riprap-covered pipeline crossings. Whilst there has been research on scour predictiondownstream of sills, the majority of work has been undertaken on unsubmerged or partiallysubmerged sills. The only experimental work on submerged sills is restricted to a range of con-ditions not applicable to large rivers. This paper presents experiments, using walnut shell asthe sediment, undertaken with a fixed flow depth but with a range of velocities and sill heights.The flow velocity utilised is substantially greater than the critical velocity for the walnut shell;conditions representative of flow in large sand-bed rivers. Hydrodynamic numerical simulationswere run for the same conditions as imposed in the flume experiments to gain insight into thecorresponding flow structure. This research demonstrates the role of submerged sill height onthe vertical velocity profile and the consequent scour depth.

Keywords: Scouring, scour depth, submerged sill


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Investigation of local scour around tandem piers for differentskew-angles

Sargol Memar ∗† 1,2, Mohammad Zounemat-Kermani 1, Ali-Asghar Beheshti 3, Giovannide Cesare 2, Anton J. Schleiss 2

1 Shahid Bahonar University of Kerman – Iran2 Ecole polytechnique federale de Lausanne EPFL – Switzerland

3 Ferdosi University of Mashhad – Iran

In the present study the effect of the skew-angle of the alignment of tandem piers on localscour depth around them is investigated. The tandem piers were aligned with different skew-angles of with respect to the flow direction. The results indicate that with the increment of theskew-angle, the influence of sheltering effects is decreased. In other word, since the shelteringeffect of the upstream pier is declined (which reduces the approach velocity for the downstreampier) the scour depth around downstream pier increases. The results show that the maximumscour depth occurs at both piers for the skew-angle of . Furthermore, the best configuration toaligned tandem piers was achieved at the skew-angle of .

Keywords: Local scour, pier, skew, angle, tandem piers


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Prediction of bridge pier scour depth and field scour depthmonitoring

Fong-Zuo Lee ∗† 1, Jihn-Sung Lai 1, Yung-Bin Lin 2, Kuo-Chun Chang 3, Xiaoqin Liu 2,Cheng-Chia Huang 1

1 Hydrotech Research Institute, National Taiwan University – Taiwan2 National Center for Research on Earthquake Engineering, National Applied Research Laboratories –

Taiwan3 Department of Civil Engineering, National Taiwan University – Taiwan

In practice, it is a major challenge in real-time simulation and prediction of bridge pier scourdepth, especially using 3-D numerical model. The simulation time spend too much to use 3-Dnumerical model simulation and inefficiently to predict bridge pier scour depth in real-time. Withheavy rainfall during flood season in Taiwan, abundant sediment with flash flood from upstreamwatershed is transported to downstream river reaches and transportation time is limited withinone day. The flood flow tends to damage bridge structures and affect channel stabilization influvial rivers. In addition, the main factors affecting the erosional depth around bridge piersand river bed stabilization are hydrological and hydrographic characteristics in river basin, thescouring and silting of river bed section near the bridge piers, the bridge geometry and protectionworks of bridge piers. Therefore, based on the observed rainfall data provided by the CentralWeather Bureau and the hydrological conditions provided by the Water Resources Agency duringflood event as the boundary condition, we develop an effective simulation system for scour depthof bridge piers. The scour depth at the bridge pier is observed by the National Center forResearch on Earthquake Engineering for model calibration. In this study, an innovative scourmonitoring system using vibration-based Micro-Electro Mechanical Systems (MEMS) sensorswas applied. This vibration-based MEMS sensor was packaged inside a stainless sphere withthe proper protection of the full-filled resin, which can measure free vibration signals to detectscouring/deposition processes at the bridge pier. It has demonstrated that the measurementsystem for monitoring bridge scour depth evolution is quite successful in the field.

Keywords: bridge pier scour depth, simulation system, scour monitoring system


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Equilibrium scour morphology downstream of rock sills underunsteady flow conditions

Stefano Pagliara ∗† 1, Michele Palermo 1

1 University of Pisa - Department of Energy, Systems, Territory and Construction Engineering(DESTEC) – Via Gabba 22, 56122, Pisa, Italy

The present study aims to analyze the equilibrium scour morphology occurring downstreamof rock-made sills with different shapes, under different inflow conditions. Namely, experimentaltests were conducted under both steady and unsteady flow conditions. In this last case, the peakdischarge was kept the same as the respective base tests performed for steady flow conditions.The scour evolution was carefully monitored, as well as the main characteristic lengths of thescour hole (e.g., maximum scour depth and axial length). The inflow discharge characteristicswere varied, i.e., the maximum peak discharge was reached by adopting different hydrographs,in order to test their influence on the equilibrium morphology. Experimental results showedsignificant similitudes in terms of equilibrium scour morphology between steady and unsteadyflow conditions when the hydrograph duration is enough long. The results of the present studycan be useful for a correct design of such structure typology in usual applications.

Keywords: Grade, control structures, river restoration, sediment transport, unsteady flow


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Wednesday 5 September, 10:45 – 12:45 Li 1 – Computational methods and code calibration

Hydrograph estimation at upstream ungauged sections on theSecchia River (Italy) by means of a parallel Bayesian inverse

methodology

Alessia Ferrari ∗† 1, Marco d’oria 1, Renato Vacondio 1, Paolo Mignosa 1, MariaGiovanna Tanda 1

1 Dept. of Eng. Architecture, Univ. Parma – Parco Area delle Scienze 181/A, Parma – Italy

The knowledge of discharge hydrographs in natural river sections is fundamental for waterresource management, design of new structures, flood modeling, etc. Direct discharge measure-ment is difficult to carry out during flood events in natural rivers; therefore, discharge hydro-graphs are usually inferred converting measured water level data by means of rating curves.However, this procedure presents several issues: (i) rating curves are seldom well calibrated forhigh discharge values, (ii) the stage-discharge relationship is not unique due to inertial and/orbackwater effects, (iii) the determination of a flood hydrograph is possible only in gauged sec-tions. Moreover, particularly challenging is the discharge reconstruction at the entrance of ariver reach, where no stage/discharge observations are available neither in the section of interestnor in any upstream ones.In this work, we present a reverse flow routing procedure, which allows to estimate dischargehydrographs at upstream ungauged stations by means of information available at downstreammonitored sites.As a flow hydrograph can be statistically analyzed as a continuous random function, the reverserouting problem is solved adopting a Bayesian Geostatistical Approach (BGA). Assuming asknown quantities the observed water levels at a downstream section, the goal is to determinethe upstream flow values (parameters). To do this, the BGA maximizes the posterior probabilityof the unknown parameters for given observations, by considering a priori information on theparameter temporal correlation and the epistemic errors associated with the studied problem.The methodology requires a forward model of the considered river reach, which must be ableto correctly describe the hydraulic routing processes. In many real cases of rivers includinglarge floodable areas, it is necessary to adopt a 2D Shallow Water Equation model to capturethe complex hydrodynamic field. However, the use of this kind of models is still limited bytheir high computational cost, since a very large number of runs must be performed during theinverse procedure. In fact, the evaluation of the Jacobian matrix, needed to test the sensitivityof the downstream water levels to the variation of each parameter, requires performing as manyindependent runs of the forward model as the number of parameters, plus one. In this work,we overcome the computational time limitations by adopting a self-developed 2D GPU-parallelnumerical model that allows achieving ratio of physical to computational time of about 500-1000(depending on the test case features). To further reduce the computational cost, also the Jaco-bian matrix evaluation has been parallelized, in order to exploit the computational resources ofany HPC cluster, including those available in the cloud.The inverse procedure has been tested by estimating the inflow hydrographs in an Italian riverreach with complex geometry, meanders and floodplains. The unknown discharge hydrographshave been estimated with and without random errors corrupting the downstream observationswith maximum deviations of ± 0.05 m. The estimation of one of these discharge hydrographshas required about 600 runs of the forward model. The adoption of a serial forward model wouldhave required more than 1 day for a single run, making the whole procedure totally unfeasible.On the other side, a GPU forward model would have estimated the discharge hydrograph in


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about 4 computational days, which is still a high amount. Conversely, the coupling betweenthe forward GPU code and the parallel procedure to calculate the Jacobian matrix allowedestimating the inflow hydrograph in ”only” 13 hours using a HPC cluster with 10 NVIDIAR© Tesla R© P100 GPUs. Since the implemented parallel version can take advantage of anyHPC cluster/cloud, hence the more GPUs are available, the less time is required for the inversemethodology.

Keywords: Bayesian inverse methodology, Reverse flow routing, Discharge estimation, Ungauged

sites

26


LiDAR resolution and catchment-inclusive hydrodynamicmodels

Graeme Smart ∗† 1

1 NZ Nat. Inst. Water & Atmos. Research (NIWA) – New Zealand

Flood inundation is highly sensitive to ground levels because critical elevation errors (mea-sured in centimetres) can result in large inundation errors (measured in square kilometres). InNew Zealand, flood hazard mapping is done at different resolutions with different degrees ofdetail and using different assumptions. The 2-dimensional hydrodynamic models used are basedon digital topography models derived from LiDAR. The LiDAR point density can vary widely(e.g. 1 point/m2 or 20 points/m2). Before National standards can be agreed it is necessary tounderstand what errors are associated with different levels of LiDAR. Effects of resolution areinvestigated by a case study model of the entire catchment and floodplain of the Waikanae River,lower North Island, New Zealand. The range of topography, infrastructure and vegetation coverin the Waikanae region represents a microcosm of conditions found across New Zealand. LiDARsorties were flown at three different heights to give three different average point densities.The Low, Medium and High point densities varied widely over the study area and the densitiesinvestigated were typically around 3-5 points/m2, 9-20 points/m2 and 25-44 points/m2 respec-tively. These densities include ground and non-ground hits. These data sets were processedinto roughness and DEM grids which were analysed and evaluated to determine suitability foraccurate hydrodynamic modelling. Three representative LiDAR tiles were used for statistics onresults from analyses made with different resolution LiDAR data. The representative tile sitesare described as: ”Urban Riverside”, ”Rural”, and ”Bush Hill Catchment”.A dynamically adaptive grid, Basilisk hydrodynamic model was used to illustrate flooding extentproduced with the different LiDAR densities. The model allowed distributed water sources (andsinks) across the topography for ”direct rainfall” modelling. The adaptive computational cellsembraced both large hillslopes at a coarse scale and small channels at a fine scale.On the basis of comparisons of results across the representative locations, the medium resolutionLiDAR (9 points/m2) provided elevation and roughness grids sufficiently accurate for hydrody-namic flood mapping of urban and rural floodplains. Low-resolution LiDAR (3 points/m2) isconsidered adequate for hill catchments. Attention is required where narrow-crested controlstructures exist. Mapping and upscaling are discussed.

Keywords: LiDAR, DEM, direct rainfall, roughness, resolution, flood hazard


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Interpolation of water surface profiles in unsteady open channelflow using the adjoint method based on two-dimensional shallow

water equations

Akihide Watanabe ∗† 1, Takashi Kojima 1, Tetsuaki Mikami 1, Matsunobu Kazuhiko 1,Hiromi Suzuta 2, Shinjiro Tomizawa 2

1 TOKEN C.E.E. Consultants Co.,Ltd – Japan2 Aero Asahi Corp. (Div. of Spatial Information) – Japan

The higher frequency of intense rainfall due to recent climatic change has increased the needfor a real-time information service for river flow conditions for residents of lowland areas livingnear to rivers. At present, the major flood services in Japan handle data from widely separatedgauge stations, and residents often find it difficult to recognize threats. Therefore, there is aneed for more information about river conditions with accurate interpolation of water levels atgauge stations. The difficulty for accurate real-time interpolation is the uncertainty of hydraulicfactors such as river flow rate, channel roughness and the effects of two-dimensional flow inducedby channel topography on water gauge measurements at river banks. In this study, an algorithmfor accurate interpolation of water stage data was investigated using the adjoint method basedon two-dimensional shallow water equations. The algorithm was applied to two flood eventsobserved in the Tone River, Japan. The adjoint method was applied to a set of shallow waterequations in a generalized coordinate system in which the hydraulic effect of tree communities isincluded in a form of semi-permeable blocks. The cost function to be minimized in the adjointmethod is expressed as follows: JT (Qbound, n,K) = JH + JQ+ Jnint + JKini

where JT is the total cost function of three uncertain control variables, Qbound the discharge atthe upstream end in the calculation, nManning’s bed roughness andK the permeability constantfor the tree communities. JT is composed of four terms: JH and JQ are the total misfit for thewater level and discharge, respectively, and Jnint and JKini are the square sum of differencesfrom the initially assumed values of n and K, respectively. The Lagrange multiplier method wasapplied to obtain an expression for functional derivatives of total cost by control variables underthe constraint of the shallow water equations. The composition of control variables correspondingto the minimum JT was obtained iteratively using the truncated Newton algorithm. The methodwas applied to two flood events observed in 2011 and 2015 over a 20 km reach of the Tone River,where four water gauges were installed. The river channel has a composite cross section with atotal channel width of approximately 800 m, and the low-water channel has an average width anddepth of 400 m and 6 m respectively. Most of the floodplain is covered by grass, but some reedcolonies and tree communities remain along the banks of the low-water channel. The channeltopography including tree community distribution with height classification data was providedby the river administration office. The computation results successfully explained the time seriesof river discharge observed at one station located in the river reach, as well as the hydrographsobserved at the four stations. In addition, the longitudinal profile of high water level showedgood agreement with the trace water levels measured at 500 m intervals just after the floodevents. Values for n and K converged to the final values within four iterations. Conversely, teniterations were necessary to obtain an optimized time series for Qbound for one time span of eighthours. However, the computation time for ten iterative calculations was only four minutes usingIBM Power8 (10 cores) processor, which means that the algorithm developed in this study canbe used for the real-time provision of continuous water surface profiles to the public.


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Keywords: Adjoint method, Data assimilation, Water surface profile, Airborne LiDAR Bathymetry,

Tone River, 2D shallow water equations

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Numerical simulation of 2D real large scale floods on GPU: theEbro River

Isabel Echeverribar ∗† 1, Mario Morales-Hernandez 1,2, Pilar Brufau 1, PilarGarcıa-Navarro 1

1 University of Zaragoza – Spain2 Dept. Soil and Water, Aula Dei Experimental Station – Spain

Modern flood risk management and mitigation plans incorporate the presence of numericalmodels that are able to assess the response of the system and to help in the decision-makingprocesses. The shallow water system of equations (SWE) is widely used to model free surface flowevolution in river flooding. Although 1D models are usually adopted when simulating long riversdue to their computational eciency, 2D models approximate better the behaviour in floodplainsof meandering rivers using a fine mesh which implies unaordable computations in real-worldapplications. However, the advances on parallelization methods accelerate computation making2D models competitive. In particular, GPU technology oers important speed-ups which allowfast simulations of large scale scenarios. In this work, an example of the scope of this technologyis presented. Several past flood events have been modelled using GPU. The physical domain(middle part of the Ebro River in Spain) has a extent of 477 km2, which gives rise to a largecomputational grid. The steps followed to carry out the numerical simulation are detailed, as wellas the comparison between numerical results and observed flooded areas reaching coincidencesup to 87.25 % and speed enhancements of 1-h of simulation time for 1-day flood event. Theseresults lead to the feasible application of this numerical model in real-time simulation tools withaccurate and fast predictions useful for flood management.

Keywords: shallow water, flood prediction, GPU computing, adaptive meshes


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Application of a 3-D CFD model to investigate flood-relatedengineering problems

Daniel Horna-Munoz ∗ 1, George Constantinescu † 1

1 University of Iowa – United States

The paper discusses the application of a fully 3-D, non-hydrostatic, RANS model with de-formable free-surface capabilities to several main types of flood-related engineering problems.The model is found to accurately simulate the dam break flow developing in a 900 open channelbend for which detailed validation data from a laboratory experiment are available. First prac-tical application deals with mitigation of flooding extent via implementation of flood protectionstructures such as floodwalls. Numerical results show that the floodwalls effectively protect thecritical regions situated in the vicinity of the river and the reduction of the flooded area withrespect to the case when floodwalls are not present is about the same at high-flow conditions andat low-flow conditions. The second application deals with prediction of flow structure around alocation containing a bridge whose deck becomes submerged as the flood wave passes the bridgelocation. The final application considers the effects of a sudden dam break failure for a damsituated upstream of the Iowa City, USA.

Keywords: numerical modeling, floods, dam break, pressure scour effects

∗Corresponding author: [email protected]†Speaker

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Advanced numerical models for the propagation of floods withhigh-sediment concentrations in mountain rivers

Marıa-Teresa Contreras 1, Cristian Escauriaza ∗† 1

1 Hydraulics and Environmental Engineering Department (DIHA) – Santiago – Chile

Rapid floods induced by extreme precipitation are common events in regions near the An-des mountain range. Rapid urban development, combined with the changing climate and theinfluence of El Nino, have increased the exposure of the population in many regions of SouthAmerica. Simulations of rapid floods in these watersheds are very challenging, due to the com-plex morphology, the insufficient hydrometeorological data, and the uncertainty posed by thevariability of sediment concentration.We develop a high-resolution numerical model of the non-linear shallow water equations, cou-pled with the mass conservation of sediment, and considering the density effects and changes ofrheology in the momentum equation. We simulate multiple cases with different sediment con-centrations in a watershed in Santiago, Chile, to understand the influence of different parameterson the flood dynamics.Based on these simulations we develop a real-time early-warning system, by creating a surrogatemodel or meta-model from the simulations. Using a small set of parameters, we define stormsfor a wide range of meteorological conditions, and utilize the high-fidelity model results to createa database of flood propagation under different conditions. Through this second model we per-form a sophisticated interpolation/regression, and approximate efficiently the flow depths andvelocities.This is the first application of its kind in the Andes region, which can be used to improve theprediction of flood hazard in real conditions, employing low computational resources. We alsocreate a framework to develop early warning systems, and to help decision makers and cityplanners in these mountain regions.

This work has been supported by CONICYT/FONDAP grant 15110017, and by the Vice Chan-cellor of Research of the Pontificia Universidad Catolica de Chile, through the Research Inter-nationalization Grant, PUC1566 funded by MINEDUC.

Keywords: flood, mountain rivers, numerical models


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Wednesday 5 September, 10:45 – 12:45 Br 1 – Sediment case studies (modelling)

One-Dimensional Modeling of Transport and Fate of Coal Ashin a River-Reservoir System

Mustafa Altinakar ∗† 1, Nuttita Pophet 1, Xiaobo Chao 1, Reza Marsooli 2

1 NCCHE, The University of Mississippi – Brevard Hall Room 327, P.O. Box 1848 University, MS38677-1848 – United States

2 Dept. of Civil & Environmental Engineering - Princeton University – E-Quad E316, Princeton, NJ08544 – United States

The present study discusses one-dimensional modeling of the coal ash spill into the DanRiver in February 2, 2014, using CCHE1D model. The simulations involved unsteady flowhydrodynamics, unsteady non-equilibrium transport of bed material and coal ash in multiplesize classes. Discharges of coal ash transport and percentages of coal ash deposited in the mixinglayer are presented. The paper presents the investigation of the sensitivity of model results tothe rise time and fall time of the triangular hydrographs of pond water and coal ash dischargesinto the Dan River, the number of size classes used for modeling bed material and coal ash, themixing layer thicknesses and the non-equilibrium adaptation length.

Keywords: Coal Ash, 1D Modeling, Sediment Transport, Sensitivity Study


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Field data and regional modeling of sediment supply toEmilia-Romagna’s river mouths

Silvia Cilli ∗† 1, Paolo Billi 2, Leonardo Schippa 3, Edoardo Grottoli 1, Paolo Ciavola 1

1 Department of Physics and Earth Sciences, University of Ferrara – Italy2 International Platform for Dryland Research and Education, Tottori University – Japan

3 Department of Engineering, University of Ferrara, Ferrara – Italy

Over the last decades, most of the Emilia-Romagna (Italy) beaches on the Adriatic sea, havebeen affected by marked erosion, which is primarily due to the reduction of sediment supplyby the local rivers. Unfortunately, despite few sporadic field studies, bed-load sediment trans-port in the region is only available for a limited number of rivers (Billi & Salemi 2004, Ciavolaet al. 2005, Ciavola et al. 2010). In order to widen the dataset of river sediment supply inthe whole region, bedload measurement campaigns in representative rivers (i.e., Fiumi Unitiand Savio rivers) are in progress. This project mainly aims to quantify the sediment flux ofthese pilot sand-bed rivers, and to create a methodology to be applied at regional scale overthe Emilia-Romagna rivers. As a preliminary step the present paper focuses on the analy-sis of threshold sediment transport condition. The main research activities essentially includehydrological analyses and field bedload transport measurement shortly upstream of the studyrivers mouth. During floods, hydraulic and sediment transport data were collected at fixedverticals, across the effective channel width. Flow depth, flow velocity and bedload transportwere measured by a standard USGS AA type current meter and a standard Helley-Smith bed-load sampler with a 76x76 mm intake, respectively. Complementary hydraulic investigation andmodelling have been performed. Repeated bed-material sampling activities have been carriedout at several flood conditions, obtaining a significant number of observations. Any sedimentyield estimation must take into consideration the threshold sediment transport condition. Tothis aim we considered three different approach, including Shields’s incipient motion criterion,based on empirical spurious power law function involving stress and representative sediment di-ameter (Carling (1983), Hammond (1984)), and on the stream power revised approach (Parkeret al. (2011)). All these criteria seem inappropriate to predict the threshold conditions for bedparticle entrainment in terms of bed shear stress. The inaccurate estimation given by theseformulae is due to the fact that they do not consider some aspects (e.g., grain-shape, sedimentsize distribution, protrusion, packing and grading) or are mainly suitable for gravel-bed rivers.Moreover the presence of bedforms suggests that further studies are needed, especially incorpo-rating their effect on the riverbed roughness. The present study aims at widening the data setof river sediment supply to the beaches of the whole Emilia Romagna region, which, in the lastdecades, were affected by marked erosion. Bedload measurement campaigns were carried out inthe mid 2000s and were relaunched in 2017. The field measurements performed so far provideddata on bedload grain size and bedload transport rates for each flood in association with flowdischarge. These results indicate that bedload sediment yield to the Romagna beaches is highlyvariable and influenced by human factors. A comparison with the results of well-known criteriato predict the threshold conditions for bed particle entrainment indicates that they are largelyinappropriate. Considering the results related to the Shields dimensionless parameter qcr, allcriteria show an order of magnitude of difference, except for Bagnold (modified by Parker) andCarling criteria.

Keywords: bedload, sandbed, sediment supply, bedload entrainment, sediment transport, threshold

condition


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The influence of transverse slope effects on large scalemorphology in morphodynamic models

Anne Baar ∗† 1, Marcio Boechat Albernaz 1, Wout Van Dijk 1, Maarten Kleinhans 1

1 Utrecht University – Netherlands

Large-scale morphology is greatly affected by the amount of downslope sediment transporton slopes transverse to the main flow direction, which determines bar length and bifurcationdynamics. Consequently, the transverse slope parameter is a crucial part of morphodynamicmodels. However, existing models have the tendency to overpredict channel depth and braidingindex, and therefore slope effects are often increased when calibrating on existing morphology.The objective of this study is to identify possible causes of the overdeepening of channels in themorphodynamic model Delft3D, and to show how different slope effect parameterisations affectmorphology in rivers and estuaries. Results show that the two methods to calculate transversesediment transport in Delft3D have a significantly different effect on the predicted morphologyand this effect is larger for environments with a large braiding index, in combination withthe sediment transport predictor of Engelund-Hansen. Results furthermore imply that evenwhen models are initially calibrated on existing morphology, results could significantly differdownstream when calibrated with a different choice of transverse slope option.

Keywords: transverse slope, sediment transport, annular flume, experiments, bend flow, Delft3D,

numerical modelling, slope effects


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A gravity-driven runoff and erosion model for sedimenttransfers at the catchment scale

Florent Taccone ∗† 1,2, Germain Antoine 1,2, Olivier Delestre 3, Nicole Goutal 1,2

1 Laboratoire d’Hydraulique Saint-Venant – Ecole des Ponts ParisTech, Electricite de France Rechercheet Developpement, CEREMA – 6 quai Watier, BP49, 78401 Chatou cedex –France

2 Laboratoire National d’Hydraulique et d’Environnement, EDF R & D (LNHE) – Electricite de FranceRecherche et Developpement – 6 quai Watier, 78401 Chatou cedex – France

3 Laboratoire de Mathematiques J. A. Dieudonne Universite de Nice-Sophia Antipolis – Parc Valrose06108 Nice – France

The aim of this work is to simulate hydraulic transfers and upstream erosion sources in steepand erodible mountain watersheds with a physically-based hydraulic model. In such environ-ments, immature debris flows and shallow landslides can be the largest sources of sedimentstransported at the outlet. To simulate these phenomena, a gravity-driven erosion model and a1D vertical infiltration model have been developed in the TELEMAC 2D numerical code. Inthis new erosion model, the motion of the granular flow is described with a fully dynamic systemand a Coulomb-like bottom friction treatment, more adapted to the properties of the flow.The new model is first qualitatively evaluated on a theoretical test case: a steep plot with a slopebreak is used to evaluate the erosion and deposition dynamics of a single immature debris flow.Then, the model is confronted to field data on a real catchment (Draix, in the Southern FrenchAlps). First, the infiltration model is successfully calibrated in order to simulate two differentrain events. Then, the new erosion model is applied at the catchment scale. The numericalresults show a very realistic behavior compared to the field observation, providing erosion in theupper parts of the hillslopes and deposition in the hydraulic network. This work opens promis-ing perspectives, for example by coupling this new model with a classical and complementaryvelocity-driven model for the erosion, deposition and transfers in the hydraulic network.

Keywords: Physically based model, debris flow, sediment transfers


36



Estimation of sand suspension in a secondary channel of analpine river

Benoıt Camenen ∗† 1, Guillaume Dramais 1, Alexis Buffet 1, Fabien Thollet 1, Chloe LeBescond 1, Mickael Lagouy 1, Celine Berni 1, Jerome Le Coz 1

1 Irstea centre de Lyon-Villeurbanne, UR RiverLY, 5 rue de la Doua - CS 20244 69625 VilleurbanneCedex – France

A significant amount of fine sediments can be found in piedmont gravel bed rivers. Mainplaces of storage are pools (Lisle & Hilton, 1992) and gravel bars where backswamp deposits areoften observed (Bridge, 1993). It remains however very difficult to estimate the total amountof fine sediments since they are easily washed out and can also infiltrate the gravel matrix.Moreover, very different dynamics can be observed from one class of sediments to another,i.e. washload of silts versus graded-suspension of sands. It is in particular a real challenge tomeasure graded-suspension of sands in such dynamic rivers where gravel bedload occurs at thesame time. The purpose of this paper is to present some field experiments to measure suspendedsediment fluxes in a secondary channel of an alpine river, the Arc River located in the FrenchAlps, during a flushing event. Very large concentrations of fine sediments in suspension weremeasured during this event, up to C = 30 g/l. These measurements however do not include sandsince they are based on a turbidity station deployed on the side of the river and calibrated usingsurface samples including clay and silt only. Specific measurements of the graded suspension inthe middle of a secondary channel were attempted using a new sampler that allows simultaneoussampling at three different levels over the bed (+5 cm, +10 cm, and +20 cm). Samples wereachieved using three ISCO samplers. Additional surface sampling were also made manually forcomparison. Samples were analyzed using the ASTM D3977 reference to correctly estimate thesand fraction, i.e. sand fraction was first sieved and analyzed separately. We then used a lasergrain sizer to obtain the Grain Size Distribution (GSD) of the finer fraction. The campaign alsoincluded topographic measurements of the gravel bar and secondary channel before and afterthe event. Ground Reference Points (GRP) were placed in order to be able to ortho-rectifymovies taken from the side bank for Large Scale Particle Image Velocimetry (LSPIV). LSPIVmeasurements were achieved during the flushing event in order to estimate surface velocitiesover the secondary channel and over the gravel bar when inundated. Pressure gauges were alsoset along the secondary channel to measure both water depth and slope. It was then possibleto estimate bed shear stress in the secondary channel during the event. A significant gradedsuspension of sand was measured even for relatively low velocities. A discussion of the sandfluxes estimated during the event will be provided together with the bed shear stress time series.In particular, semi-empirical formulas developed for sand suspension will be applied and theirability to predict sand flux in alpine rivers will be tested.

Keywords: sand suspension, in situ measurement, alpine river


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Performance of a groyne in controlling flow, sediment andmorphology around a tributary confluence

Kohji Michioku ∗† 1, Yuki Osawa 2, Keiichi Kanda 3

1 Department of Civil and Environmental Engineering, Faculty of Engineering and Design, HoseiUniversity (Hosei University) – 2-33 Ichigaya-Tamachi, Shinjuku, Tokyo 162-0843, Japan

2 Tokyu Corporation (Tokyu) – Japan3 Department of Civil Engineering, National Institute of Technology, Akashi College (Akashi College) –

679-3 Nishioka, Uozumi-cho, Akashi, Hyogo, 674-8501, Japan

Performance of a groyne in controlling flood flow, sediment transport and river morphologywas investigated in a middle stream reach of Kako River, Japan. A major tributary perpen-dicularly joins the main stream there and the flow is strongly influenced by the back waterstretched from a barrage at 4km downstream. It is considered that the water impounded bythe barrage predominantly affects hydro- and morphodynamics in the upstream reach, whichhas brought a significant change in fluvial process around a tributary confluence in the last twoand a half decades after construction of the barrage. Typical irreversible morphological changeswhich appeared in the reach are growth of a huge sandbar in front of the confluence, thalwegmigration from the left to right bank, erosion of the main channel and sedimentary deposit onthe floodplain. Such a morphological regime shift brings serious issues not only in flood controland management but also in ecosystem and hydrophilic activities. As a trial countermeasureagainst the problems, a groyne was constructed with concrete block mound at the left bankupstream of the confluence in 2014. However, it is not yet known at this moment if the groynecould improve and rejuvenate river morphology in the future as we expect. The present studyis to estimate how the groyne will modify and control hydrodynamic and fluvial processes inthis reach. In order to examine the effects of the groyne properties on flood flows and riverbed profile, a two-dimensional shallow flow model was applied to analyze hydrodynamic andfluvial processes during flood events for various patterns of length, height, installation angle andlocation of the groyne. The analysis on thirty years of morphological change suggests that thesandbar developing in front of the confluence tends to shrink and the thalweg tends to returnto the original position in the case of the present arrangement of groyne. Namely, it is expectedthat the present groyne may maintain the channel’s conveyance capacity and rejuvenate rivergeomorphology. On the other hand, the sandbar was found to grow furthermore, if the groynewas constructed on the right bank side. It was also verified that the geomorphology is scarcelyinfluenced by the installation angle of groyne, while erosion of thalweg and sedimentation onfloodplain are well controlled by the length and height of the groyne. Time-development of twoparameters, i.e. area and kurtosis of the bed profile in cross sections, was analyzed for variousarrangement patterns of the groyne in order to examine the performance of a groyne in main-taining channel’s conveyance capacity and creating ecologically desirable bathymetry. From theviewpoints not only of flood control but also of natural environment, the best scenario of groynearrangement was proposed based on the parametric analysis.

Keywords: Groyne, sandbar, thalweg, confluence


38


Wednesday 5 September, 14:10 – 16:10

Wednesday 5 September

14:10 – 16:10

BC 2 – Vegetation and sediment transport . . . . . . . . . . . . . . . . 40

Me 2 – Suspended sediment fluxes . . . . . . . . . . . . . . . . . . . . . 46

Li 2 – Sediment modelling . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Br 2 – Fishways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

39

Wednesday 5 September, 14:10 – 16:10 BC 2 – Vegetation and sediment transport

Influence of flood regime on riparian vegetation dynamics inrivers with alternate bars

Camille Jourdain ∗† 1, Nicolas Claude 2, Germain Antoine 1,2, Pablo Tassi 1,2, FlorianCordier 2

1 Laboratoire d’Hydraulique Saint-Venant – Ecole des Ponts ParisTech, Electricite de France Rechercheet Developpement, CEREMA – 6 quai Watier, BP49, 78401 Chatou cedex – France

2 Laboratoire National d’Hydraulique et Environnement (LNHE) – EDF R & D – Quai Watier, Chatou– France

Throughout the 20th century, many rivers worldwide have undergone important riparianvegetation encroachment, which can be problematic in terms of flood risks and biodiversity.Nowadays, controlled floods is often considered as a management option in anthropized rivers,with the aim of limiting vegetation encroachment within river channels, as well as maintaininga diverse habitat by reactivating natural channel dynamics. In this context, this study aims atinvestigating the influence of different flood regimes on river bar vegetation development anddynamics, focussing on alternate bar systems which are typically found in embanked streams.This question has been addressed through two-dimensional bio-morphodynamic modeling of asimplified gravel bed river reach. Four hydrological scenarios with different flood peak dischargeshave been run for 50 years. For all scenarios, a steady increase in vegetation cover stronglyimpacts the evolution of bar morphology, until a relatively stable equilibrium is reached after oneto three decades. Numerical results suggest that vegetation development on bars is associatedto an increase in bar wavelength and a decrease in bar width. Higher peak flood dischargeslead to narrower and longer bars, and a longer adjustment duration. When vegetation cover isfully developed, interannual flood variability seems crucial to maintain bedform and vegetationturnover.

Keywords: river morphodynamics, biogeomorphology, alternate bars, riparian vegetation, numeri-

cal modeling


40



Effect of vegetation on flows and sediment transport

Soualmia Amel ∗ 1, Romdhane Hela † 1, Ludovic Cassan 2, Gilles Belaud 3

1 National Agronomique Institut of Tunisia (INAT) – Tunisia2 National Institut Polytechnique of Toulouse – Institut of Fluid Mechanics of Toulouse – France

3 Institut national d’etudes superieures agronomiques de Montpellier (Montpellier SupAgro) – UMRG-eau – 2, place Viala 34060 Montpellier Cedex 2, France

Vegetation is a common feature in natural coastal and riverine waters, interacting with bothwater flow and sediment transport. However, the physical processes governing these interactionsare still poorly understood, which makes it difficult to predict sediment transport and associ-ated morphodynamics in a vegetated environment. In this context, an experimental study wasconducted in laboratory with a movable bed trapped in artificial vegetation. The experimentalflume is a rectangular open channel 5.75 m long and 0.29 m wide. For flow measurements, thechannel is equipped with a fast camera and ADV probe. This work focuses on identifying thevegetation effects on flows and sediment transport. In fact, it was shown that the vegetationpresence in a watercourse promotes deposition and sediment accumulation. This is explainedby a reduction of the bed shear stress, since the friction occurs mainly by the drag force effectexerted by the vegetation. It was shown too that the vegetation reduced the bedload transport.Thanks to the partitioning of shear stress, it was possible to predict the bedload transport usingstandard formulas with a reasonable accuracy.

Keywords: vegetation, sediment transport, experimental study, channel


41



Transport and deposition of fine sediment in a channel partlycovered by flexible vegetation

Walter Box ∗† 1, Kaisa Vastila 1, Juha Jarvela 1

1 Aalto University School of Engineering – Department of Built Environment, PO Box 15200, 00076Aalto, Finland

Riparian plants exert flow resistance and largely influence the flow structure, which affectserosion, deposition and transport processes of fine sediments. Predicting these vegetative effectsis important for flood, sediment and nutrient management. However, predictions on the fateof sediments are complicated by uncertainties associated with the suitable parameterization ofnatural plants and the associated effects on the turbulent flow field and on the variables inthe transport equations. The aim of this study is to quantify deposition and transport of finesandy sediment in a partly vegetated channel under laboratory conditions. Care was takento reproduce conditions typical of vegetated floodplain flows including dense flexible grassyunderstory as a starting point. The experiments were conducted in a flume that is specificallydesigned to recirculate fine sediment. We measured suspended sediment concentrations withoptical turbidity sensors and determined patterns of net deposition over the vegetated partsof the cross section. The flow field was determined with acoustic Doppler velocimetry. Ourinvestigations are intended to improve future predictions of fine sediment storage and transportin natural or constructed vegetated channels, and the first results reported herein were useful indesigning further, on-going experiments with complex combinations of vegetation and channelgeometry.

Keywords: sediment transport, suspended sediment, deposition, riparian vegetation, flow field


42



Flume experiments on vegetated alternate bars

Giulio Calvani ∗† 1, Simona Francalanci 1, Luca Solari 1

1 University of Florence, Department of Civil and Environmental Engineering (DICEA - UNIFI) – viaS. Marta, 3 50139 Firenze, Italy

The planform morphology of a river reach is the result of many processes involving the motionof sediment (erosion, transport and deposition), the hydrological regime and the developmentand growth of vegetation. The combined action of these three processes affects the evolution ofthe riverbed modifying the channel slope, the cross-sectional shape and the local radius of riverbends. Despite the simple relations involved for modelling vegetation dynamics (colonization,growth and decay), numerical simulations have proved that riparian plants have a significant roleseveral processes, such as reducing braiding degree and promoting single-thread channel (me-andering) (e.g., Bertoldi et al., 2014). However, the interactions among these processes are stillpoorly understood and rarely investigated in laboratory flume experiments (e.g., Tal and Paola,2010). In these experiments and also in numerical modelling, vegetation is usually representedby rigid cylinders, although it is widely recognized that this schematization cannot reproducethe effects of root stabilization and binding on riverbed sediment (Vargas-Luna et al., 2016).In this work, we focus on the effects of added vegetation on morphological initiation, develop-ment and dynamics of alternate bars in straight channel by means of flume experiments. Weperformed laboratory experiments reproducing hydraulic conditions that are typical of gravelbed rivers, in terms of water depth, bed slope and bed load; in particular, alternate type of barswere reproduced.We employed both rigid and flexible vegetation. The vegetation was deployed on the alternatebars according to field observations carried out in the Arno river. Various vegetation scenarios,in terms of density and spatial arrangement, were implemented in the flume experiment suchto mimic different maintenance strategies. Measurements of flow field and bed topography weresystematically taken during each experiment.Results show the effect of vegetation on the alternate bar characteristics (amplitude and wave-length) and velocity of migration.

Keywords: vegetation, morphodynamics, alternate bars, flume experiments


43



Flow structure around an actual willow patch under differentdepth conditions

Chanjoo Lee ∗† 1, Donggu Kim 1, Sungjung Kim 1, Un Ji 1, Ji-Hyun Kim 1, DongwooKo 1

1 Korea Institute of Civil Engineering and Building Technology (KICT) – South Korea

Recently, vegetation is one of the key factors in river management where environmentalaspects as well as flood protection should be taken into consideration. Because of this, numerousstudies have been done including experiments and hydrodynamic modeling. Because most ofexperimental studies were made in indoor laboratory flumes with artificial trees, there are stilllimitations in transfer of their result to actual channels.Since 2009, River Experiment Center of Andong, Korea has been operating three real-scale,nature-like outdoor experimental channels. In the first straight channel (A1), several 4 (long) x2 (transverse) m actual willow patches were planted and have been grown last three years forstudies on flow vegetation interaction.A set of intensive flow measurement was made around the first upstream willow patch usingADVs and a LSPIV, together with measurement of vegetation properties. The experimentswere made under several different depth conditions from half to full height of the willow. As aresult, distribution of 3-dimensional velocity around and through the patch was characterizedalong with vertical profiles. 2-dimensional surface velocity field was also visualized. The resultsof the experiment enhance understanding on interaction of flow and actual vegetation in a naturalchannel and may also provide information on flow resistance used for hydrodynamic modelingand validation.

Keywords: flow structure, actual vegetation, REC, experiment


44



Roots Characteristics of a flexible and mature vegetation:preliminary results of experimental investigation in a

meandering laboratory flume

Donatella Termini ∗ 1, Alice di Leonardo † 1

1 University of Palermo (Italy) (DICAM) – Italy

Vegetation controls sediment dynamics and affects the kinematic characteristics of flow inrivers. The uprooting mechanism is strongly affected by mechanical properties, morphology andbranching of the roots system. This work presents preliminary results of experimental workconducted in a laboratory meandering flume. The work aims to investigate how the geometricaland mechanical characteristics of the roots of a real, flexible and mature vegetation could varyalong the bend. Results show that both the geometrical and the mechanical characteristics ofthe roots assume higher/lower values in peculiar sections of the bend suggesting that they couldbe affected by the kinematic characteristic of flow.

Keywords: river, vegetation, roots


45


Wednesday 5 September, 14:10 – 16:10 Me 2 – Suspended sediment fluxes

Suspended sediment dynamics by event typology and itssiltation effect in a semi-arid snowmelt-driven basin

Agustın Millares ∗† 1, Antonio Monino 1, Sergio Arjona 2, Asuncion Baquerizo 1

1 Group of Environmental Fluid Dynamics, Andalusian Institute for Earth System Research -University of Granada (IISTA) – Spain

2 Andalusian Regional Government – Spain

Soil loss and transport processes are key issues to understand erosive and sedimentary dy-namics in semi-arid environments. The aim of this work was to characterize the erosive patternsof different types of events and to analyse their effect downstream in a mountainous semi-aridwatershed. With that purpose, different events have been typified according to atmosphericand hydrological descriptors from information of 1) historical meteorological data, 2) resultsof simulations from physically-based and distributed hydrological modeling, which includes thesnowmelt dynamics, and 3) available MODIS satellite images. For each event, water sampleswere taken by an automatic measuring device and analysed to determine the suspended sedi-ment loads. The results allowed to identify three types of events. Among them, the maximumvalues of the measured suspended solids during rainfall-dominated events, with little snow in-fluence, were an order of magnitude higher than the snowfall-dominated events, with values of25000 mg/l versus 2500 mg/l respectively. The response of intermediate events, despite of lowflow, showed a significant gradient. The results highlight the great dynamic variability of thesediment yield along the basin and the importance of the snow in the lamination of the erosiveprocesses and their consequences on reservoir siltation.

Keywords: semi, arid environments, suspended sediment, event typology, snowmelt/rainfall frac-

tion, reservoir siltation


46



Geomorphological factors influencing hysteresis patternsbetween suspended load and flow rate in Alpine rivers

Clement Misset ∗† 1,2,3, Alain Recking 1,2, Cedric Legout 1,3, Alain Poirel 4, MarineCazilhac 4

1 Universite Grenoble Alpes – 38041 Grenoble – France2 Irstea centre de Grenoble, UR ETNA – St-Martin-d’Heres – France

3 Institut des Geosciences de l’Environnement (IGE) – IRD, INPG, INSU, CNRS, UGA – GrenobleCedex 9, France

4 EDF - Division Technique Generale (DTG) – 21 rue de l’Europe - 38040 Grenoble cedex 09 – France

Suspended sediment load represents a large part of total solid fluxes transported in mostrivers. Thus, for hydropower plan management or for environmental issues, it is crucial tounderstand how these sediments are produced, stored and transported in a given catchment.Hysteresis loops in discharge-suspended load signals are commonly used to assess sedimentsources and production processes but most of the time the shape of this relation is analyzedqualitatively on short time series or for few events.In this study we analyze quantitatively 10 long time series of suspended sediment load of variousalpine catchments. For each series a normalized hysteresis index developed by Lloydet al. (2016)was calculated. This method allows us to compare events and to assess to which extent the finesediments originate from hillslope erosion processes or from river bed remobilization.We found that watersheds having braided bed morphology are dominated by clockwise loopswhile those with narrower bed as step-pool morphology are dominated by counter-clockwisehysteresis or have no general trend. In addition, we found a significant seasonal variabilityof hysteresis shape. For instance, braided rivers have their maximum intensity of clockwisehysteresis in autumn and winter whereas hysteresis intensity decreases in spring and attains alower level in summer.These results suggest that storage and remobilization of fine sediments within the bed couldplay a major role in suspended sediment transport in Alpine streams, especially in large braidedrivers. In these systems, clockwise hysteresis responses are observed when bars and secondarybraided channels are connected to the main flow whereas periods with flows constrained in themain channel are characterized by counterclockwise or no hysteresis.A better understanding of these complex interactions between sediment and morphology, as wellas its seasonal component,could help to optimize the management of low head dams dependingof the type of hysteresis to reduce reservoir siltation and improve sediment continuity in rivers.

Keywords: suspended sediment transport, hysteresis, catchment scale analysis


47



Sediment rating and annual cycles of suspended sediment inGerman upland rivers

Thomas Hoffmann ∗† 1, Jan Blothe 2, Gudrun Hillebrand 1

1 Federal Institute of Hydrology (BfG) – Am Mainzer Tor 1 56068 Koblenz, Germany2 Department of Geography - University of Bonn – Germany

Suspended sediment load dominates the sediment transport of almost all lowland riversof the world and provides an important transport medium for pollutants and contaminants.Achieving a good ecological and chemical status of river systems, as required for instance bythe European Water Frame directive, therefore asks for a sound understanding of the sources,transport mechanisms and sinks of suspended sediment. However, these sources and sinks ofsuspended sediment and the resulting concentration in the river water are by no means constantthroughout the year.Here we present an analysis of the annual variability of suspended sediment concentrations(SSC) in major rivers draining the German upland. We take advantage of the long-term sus-pended sediment monitoring network of the Federal Waterways and Shipping Administration(Wasserstraßen- und Schifffahrtsverwaltung des Bundes, WSV) that monitors daily water fluxand SSC at ˜70 stations in Germany. Using the data of (at least) 10 stations, we analyzethe variability of rating curves with the annual climate and land cover changes, and assess theannual behavior of discharge and SSC.All stations analyzed show a consistent counterclockwise hysteresis effect between SSC and dis-charge on an annual basis. For a given discharge, SSC values are significantly higher duringsummer months (> factor two) as compared to the winter months. Preliminary results suggestthat this effect might partly be induced by rainfall intensity that adds the necessary energy tomobilize sediments in intensive summer storms. But also land use practices, exhaustion effectsand the activation of different sediment sources and sinks are amongst the possible explanatoryvariables. The selective activation of different sources is further supported by a distinct kink inthe sediment rating curves of all rivers, where the linear relationship (in a log-log plot) suddenlyshows significantly increased slopes.

Keywords: suspended sediment concentartion, rating curve, hysteresis, NDVI


48



Establishment of a rating curve for suspended sedimenttransport by means of ADCP measurements

Nils Ruther ∗† 1, Rui Aleixo 2, Massimo Guerrero 2, Sigurd Søras 3, Siri Stokseth 4

1 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology(NTNU) – S.P. Andersens vei 5, 7491 Trondheim – Norway

2 Universita di Bologna – Via del Lazzaretto 15/5, 40126 Bolonha – Italy3 Multiconsult ASA – Nedre Skøyen vei 2, 0276 Oslo – Norway

4 Statkraft AS – Lilleakerveien 6A, 0283 Oslo – Norway

The global development of hydropower is an important step towards a low-carbon society.However, in regions with large hydropower potential such as South-East Europe, Asia, Africaand South America sediments and sedimentation processes are core challenges that need tobe addressed and amended to ensure sustainable hydropower development. Sedimentation anderosion processes have proven to be technically, economically and socio-ecologically, challenging.Additionally, climate change is projected to cause increased sediment catchment yield, affectingthe operation and maintenance of the hydropower plants and hence energy production.In order to make the energy production and the use of the reservoir sustainable, the designand operation of a hydropower plants have to be based on high quality data series of sedimenttransport in space and time in the adjacent rivers. As it is per today, it takes relatively much timeto take physical samples from the river and then investigate the samples in the laboratory forthe concentration and grain size distribution. In addition, it is difficult or sometimes impossibleto measure at higher discharge due to physical limitations of the measurement devices as wellas due to health and safety regulations. Unfortunately, these high discharges are responsiblefor the high discharges of sediment loads. Consequently, the calculated total load over the yearis usually strongly underestimated. The aforementioned shortcomings, being cost intensive andunreliable, make it necessary to develop and verify cost-effective methods for sediment transportmeasurements.Therefore, this study is presenting the application of a method to quantify suspended transportload in a reach of the Devoll river upstream of the Banja hydro power plant in Albania. Themethod relates sound attenuation to suspended load concentrations as well as to grain size, andallows to obtain values every 30 – 60 min over almost the full range of the discharge prevailingin this river. The presented data series of a period of 18 month give insight in the suspendedsediment transport and velocity measurements in a form of time series allowing to identify anddiscuss various physical processes.

Keywords: Suspended load, measurements, ADCP, hydropower, sustainable design


49



Getting information on suspended sediments in a large riverfrom acoustic backscatter

Adrien Vergne ∗† 1, Jerome Le Coz 1, Celine Berni 1

1 Irstea centre de Lyon-Villeurbanne UR RiverLy – 5 rue de la Doua, CS70077 69 626 VilleurbanneCedex, France

There has been a growing interest in the last decade in extracting information on SuspendedSediment Concentration (SSC) from acoustic backscatter in rivers. Quantitative techniques arenot yet eective, but acoustic backscatter already provides qualitative information on suspendedsediments. In particular, in the common case of a bi-modal sediment size distribution, correctedacoustic backscatter can be used to look for sand particles in suspension and provide spatialinformation on their distribution throughout a river crosssection. We present a case-study wherethese techniques have been applied.

Keywords: hydroacoustics, acoustics, suspended sediments, sediment measurement, field measure-

ment, sediment load


50



Phenomenological description of scaling laws of sedimenttransport

Subhasish Dey ∗† 1, Sk Zeeshan Ali 1

1 Indian Institute of Technology – Kharagpur - 721302 – India

The phenomenological theory of turbulence was accredited to Kolmogorov’s (1941) pioneeringcontributions to the scaling laws of the fully developed homogeneous and isotropic turbulence.The phenomenological theory allows us to anticipate the scaling laws of classical problems ofsediment transport in a simplified way demanding less heuristic arguments. The advantage ofthis theory to analyse a problem is that this theory provides a universal relationship, unlike theempirical laws, by linking the dependent and the independent variables. However, this theorycannot predict the multiplicative constant linking the dependent and the independent variablesand thus, the multiplicative constant must be obtained from experimental data.In fluvial hydrodynamics, a threshold velocity is referred to the average flow velocity Uc which issufficient to begin the sediment particle motion at the bed surface. This phenomenon is calledthe threshold of sediment motion (Shields 1936, Dey 2014). We discover that at the thresholdof sediment motion, the densimetric Froude number [= Uc/(∆gd)1/2, where ∆ is the submergedrelative density of sediment particles, (∆ = ρp/ρs; ρp is the mass density of sediment particle;ρf is the mass density of fluid; g is the gravitational acceleration; and d is the particle size]follows a ”(1 + s)/4” scaling law with the relative roughness number (ratio of particle size d toflow depth h). Here, s is the energy spectral exponent.When the flow velocity surpasses the threshold velocity, the sediment particles are set in motion.Under this circumstance, the applied bed shear stress τ0 exceeds the threshold bed shear stressτ0c and the transport of sediment particles occurs within a thin layer (known as the bedloadlayer), in the form of successive contacts of the particles with the bed. This phenomenon iscalled the bedload transport. This study reveals that for the bedload transport, the bedloadtransport intensity follows the ”3/2” and ”(1 + s)/4” scaling laws with the transport stagefunction and the relative roughness, respectively.Scour in a contracted stream is one of the fascinating problems of sediment transport. The flow isaccelerated convectively in the contracted portion because of the concentration of streamlines inthe contraction. This yields a higher flow velocity that erodes the sediment bed in the contractedportion. We find that for the scour in a contracted stream, the dimensionless scour depth followsthe ”4/(3 − s)”, ”−4/(3 − s)” and ”−(1 + s)/(3 − s)” scaling laws with the densimetric Froudenumber, the channel contraction ratio and the relative roughness, respectively.The scaling laws obtained from this study in different regions of turbulent energy spectrumare extensively validated by the experimental data and the empirical relationships. This studythus faithfully sheds light on the fundamental origin of the scaling laws of sediment transportproblems by elucidating the linking between the sediment transport laws and the turbulentenergy spectrum.

Keywords: Fluvial hydraulics, turbulent flow, sediment transport


51


Wednesday 5 September, 14:10 – 16:10 Li 2 – Sediment modelling

Fluvial sediment transport: From the beginnings into the future

Willi H. Hager ∗† 1

1 ETH Zurich – Switzerland

Fluvial sediment transport is a fundamental issue in open channel hydraulics and riverengineering. It appears that the research agenda was more or less closed some 40 years ago, giventhat the small advances along with no more funding. What are the causes for these changesin river engineering?; Why has sediment transport not yet received a renaissance in researchactivities?; and What could be future research topics in this research field? Based on a state-of-the-art until the end of WWII, the author intends to forward reasons for a fresh reconsiderationof this fascinating research topic, based on the current knowledge, and particularly on therecent advances in hydraulic experimentation. Given the many questions from the communityof practicing engineering, sediment transport should be a topic to be redeveloped by the modernriver engineer. The current knowledge is simply insufficient to deal with the many questionsto be solved not only from the hydraulics community, but also from questions posed by theenvironmental, the natural resources, or the chemical engineer. This research thus does not onlyattempt to review the origins in sediment transport, but also would like to foster discussions

Keywords: Experimentation, history of hydraulics, instrumentation, open channel hydraulics, sed-

iment transport


52



Coupled method for the numerical simulation of 1D shallowwater and Exner transport equations in channels with variable

cross-section

Sergio Martınez-Aranda ∗† 1, Javier Murillo 1, Pilar Garcıa-Navarro 1

1 LIFTEC-CSIC, University of Zaragoza – Spain

This work is focused on the a numerical finite volume scheme for the resulting coupledshallow water-Exner system in 1D applications with arbitrary geometry. The mathematicalexpression modeling the the hydrodynamic and morphodynamic components of the physicalphenomenon are treated to deal with cross-section shape variations and empirical solid dischargeestimations. The resulting coupled system of equations can be rewritten as a non-conservativehyperbolic system with three moving waves and one stationary wave to account for the sourceterms discretization. But, even for the simplest solid transport models as the Grass law, to finda linearized Jacobian matrix of the system can be a challenge if one considers arbitrary shapechannels. Moreover, the bottom channel slope variations depends on the erosion-depositionmechanism considered to update the channel cross-section profile. In this paper a numericalfinite volume scheme is proposed, based on an augmented Roe solver (first order accurate intime and space) and dealing with solid transport flux variations caused by the channel geometrychanges. Channel cross-section variations lead to the appearance of a new solid flux source termwhich should be discretized properly. Comparison of the numerical results for several analyticaland experimental cases demonstrate the effectiveness, exact well-balanceness and accuracy ofthe scheme.

Keywords: Bedload transport, Source terms discretization, Arbitrary geometry, Finite Volume

Methods, Erosion and deposition mechanisms


53



Three dimensional simulation of non-uniform sedimenttransport based on multi-phase Eulerian approach: application

to debris flow

Kazuyuki Ota ∗† 1, Hitoshi Suto 1, Takahiro Sato 1

1 Institute of Electric Power Industry – Japan

In last few decades, three dimensional (3D) numerical simulation of solid-liquid multi-phaseflow has been actively discussed. However, it is still difficult to simulate 3D high-concentratedsediment laden flow such as debris flow, because they cannot be represented by means of bed-material load (i.e., bed load or suspended load). In order to simulate such a high-concentratedflow, Discrete Element Method (DEM) coupled with fluid dynamics model is being widely used.However, due to its heavy computational cost, more practical numerical method are demandedto apply a numerical model to an actual field.Recently, Eulerian-Eulerian approach is also used for 3D simulation of sediment-laden flow suchas sheet flow or local scour around hydraulic structure. These models use momentum equationsfor both water phase and particle phase, including the closure of water-particle and particle-particle interactions. However, existing studies of the Eulerian-Eulerian approach have assump-tion of sediment transport of uniform sized sediment. Thus, the sediment size segregation is notsimulated in the existing studies. However, the sediment size segregation in debris flow stronglyaffects its flow property and collisional force on the structure. Therefore, a novel numericalmodel is required to simulate of non-uniform and high-concentrated sediment transport fromscientific and practical viewpoints.This study develops the 3D multi-phase Eulerian model for non-uniform sediment-laden flow.The model was validated with several experiments of the large-scale debris flow. The basicequation consists of mass conservation equation and momentum balance equation for the waterphase and particle phase. (Please see the supplementary data) Numerical model was validatedin the large-scale debris flow experiments which obtained experimental data of flow, deposition,and sediment size segregation. The experiment was conducted using the flume of 95m-length,2m-width, and 31-degree. In the initial condition, non-uniform sediment of d50 = 5.0 mm wasset at the upstream end of the flume. The debris flow deposits at run-out (bed slope of 4-degree)equipped at the end of the flume. Two experimental cases were conducted for the flumes withroughness (16mm-height and 50mm-space) and without the roughness.In nunmeical simulatiuons, the particle size distribution was divided into 5 classes for simula-tions. Bed boundary of water flow velocity was set to Non-slip condition for all simulations. Inorder to consider the effect of artificial roughness of experiments, two boundary conditions ofparticle velocity were attempted. One is the Non-slip condition. The other one is the Partial-slip condition of Johnson and Jackson which compute the slip-velocity considering the particleconcentration and collisional force on the bed.Results of experiments and simulations were compared regarding (1) velocity of the front ofthe debris flow, (2) flow depth at a certain flume location, (3) observation of the sediment sizesegregation, and (4) deposition pattern. Both experimental cases with or without roughnessshowed famous inverse grading phenomenon which collects larger sized particle at the surface ofthe flow. However, experimental results are quite different between cases with or without rough-ness. In a case with roughness, the front of the flow decelerates after forming high-concentratedand dry gravel aggregation at the front (gravel snout). More wet and fine sediment forms behindthe gravel snout in the debris flow. In a case without roughness, flow velocity of the front almost


54



kept constant.Numerical model well captured the velocity, flow height, and sediment size segregation of theunsteady debris flow with or without artificial roughness. Note that sediment size segregationoccurs at not only longitudinally plane but also laterally, especially in the deposition process.Such a 3D size segregation were also captured the present numerical model. Therefore, thevalidity and advantage of the numerical model was demonstrated through all validation. Thecontribution of stress tensors , , were also discussed based on the numerical results.Although this work focused on the debris flow, the present numerical model also has advantageon the phenomenon which the velocity difference between water and particle is significant. Oneexample is sediment abrasion phenomenon on hydraulics structures of hydroelectric facilities.Thus, the present model has wide potential to contribute the engineering related to river.

Keywords: Multi, phase Eulerian method, debris flow, particle, size segregation, mixed, size sedi-

ment

55


Application of a Eulerian two-phase flow model to scourprocesses

Antoine Mathieu ∗1 , Tim Nagel1 , Cyrille Bonamy1 , Julien Chauchat †1 , Zhen Cheng2

, Xiaofeng Liu3 , Tian-Jian Hsu4

1 LEGI, Grenoble-INP, CNRS, France – Universite de Grenoble Alpes – France2 Woods Hole Oceanographic Institution – United States

3 Department of Civil and Environment Engineering, Penn State University – United States4 Department of Civil and Environmental Engineering, University of Delaware – United States

Over the last decades, significant research efforts have been devoted to modeling sedimenttransport using two-phase flow models either with Eulerian-Lagrangian or Eulerian-Eulerian ap-proaches. Contrary to classical sediment transport models relying on empirical formula for thebed-load and pickup flux for suspended-load, these new models are based on physical groundsallowing for in-depth investigation of sediment transport mechanisms at the intermediate scale,i.e. ranging between the particle scale and the mean flow length scales. Recently, we have devel-oped a community multi-dimensional Eulerian two-phase flow sediment transport model underthe platform OpenFOAM (https://github.com/sedfoam/sedfoam). The aim of this presentationis to present some recent developments and the application of the model to scour around struc-tures. Preliminary results on turbidity currents will also be shown.As a first step for the verification of the model, a numerical investigation of unidirectional sheetflows using unidimensional vertical simulations are presented and compared with available ex-perimental data. These verifications allow to calibrate the free parameters of the granular stressand turbulence models in order to get quantitative predictions of sediment transport rate in arange of Shields parameters above 0.1. Different combinations of granular stress and turbulencemodels have been tested. Overall, the results are less sensitive to the choice of the turbulencemodel. However, a stronger sensitivity is observed for choice of the granular stress model (kinetictheory of granular flows or granular rheology).In a second part, the application of the Eulerian two-phase model to the scour phenomenon belowa pipeline and around a cylindrical pile will be presented. For the pipeline case, we demonstratethat the model is able to quantitatively reproduce the three stages of scour, namely the onset,the tunneling and the lee-wake erosion stages. For the scour around a cylindrical pile, the modelfavorably compares with Roulund et al. (JFM 2005) experimental for the scour depth upstreamand downstream the pile over the first 5 minutes of dynamics. For these applications, a k-omegaturbulence model is used to accurately predict the flow dynamic induced by the existence of ad-verse pressure gradient. The k-omega model from Wilcox (2006) is shown to be relevant for scoursimulations. In the 3D case, the analysis of the local sediment transport rate versus the localShields number show that the two-phase flow model predicts transport rates in consistence withMeyer-Peter and Muller (MPM, 1948) formula except at the lee-side of the pile where the localsediment transport rate is about one order of magnitude higher than the one predicted by theMPM formula. This illustrates the potential of three-dimensional two-phase flow simulations toreproduce sediment transport and morphological evolution in rather complex geometries. Thisproof of concept is a first step toward simulations around complex structures for which classicalsediment transport models are doing a poor job in terms of predictive capability.

Keywords: sediment transport, two, phase flow model, scour


56



The 3D numerical study on flow and sediment properties of ariver with grouped spur dikes

Xun Han 1, Pengzhi Lin ∗† 1, Gary Parker 2

1 Sichuan University (SCU) – State Key Laboratory of Hydraulics and Mountain River Engineering,Sichuan University, Chengdu, 610065, China, China

2 University of Illinois Urbana and Champaign – Department of Civil and Environmental Engineering,University of Illinois Urbana and Champaign, Champaign, IL, 61801, USA, United States

A 3D numerical model named NEWTANK is employed to investigate the flow motion andsediment transport in grouped spur dikes system. This model is based on the Navier-Stokesequations, adopting the Volume of Fluid (VOF) method to track the free surface motion, whilethe solid is described by using the Porous Media Method (PMM). The Large Eddy Simulation(LES) is applied to capture turbulence. In sediment calculation parts, the suspended load andbedload are treated separately but combined together to update bed variation eventually. Thefinite difference form and Two-step Projection Method are employed in the process of discretizingthe governing equation. Several carefully selected flume experiments are introduced to verifythis model’s reliability before its application on the simulation of grouped spur dike case, anddetailed flow characteristics and sediment properties are analyzed afterwards.

Keywords: Grouped spur dikes, 3D numerical model, flow motion, sediment transport.


57



Large-eddy simulation study of turbulent flow around arectangular spur dike

Seokkoo Kang ∗† 1

1 Department of Civil and Environmental Engineering, Hanyang University - Seoul – South Korea

High-resolution large-eddy simulation (LES) is carried out for investigating three-dimensionalflow fields around a rectangular spur dike installed in an open-channel flume. The LES showedgood agreement with the measurement obtained using Acoustic Doppler Velocimetry. Analysisof the LES result shows that the flow structure around and in the wake of the spur dike is highlycomplex and three-dimensional. Namely, flow upstream of the spur dike is featured by a vortexsystem near the bed, another vortex system beneath the free surface, and a recirculation regionin front of the spur dike. All of these flow structures are laterally oriented. Moreover, flow inthe wake region consists of a large vertically oriented recirculation region and a smaller laterallyoriented recirculation region near the bottom corner downstream of the spur dike.

Keywords: large eddy simulation, spur dike, open channel flow, turbulent flow, computational fluid

dynamics


58


Wednesday 5 September, 14:10 – 16:10 Br 2 – Fishways

Fish behavior and fish guidance at hydro power intake screensfor fish protection and downstream passage

Franz Geiger ∗† 1, Cuchet Mathilde 2, Peter Rutschmann 1

1 Technical University of Munich – Germany2 Ecohydraulic Consulting Cuchet – Germany

Fish behaviour investigations under controlled laboratory conditions but nature like envi-ronment were conducted to clarify the efficiency of inclined and horizontal screen planes for fishprotection and fish downstream passage at hydropower plants concerning different potamod-romous species and various sizes. The dependency on the underlying geometric and hydraulicparameters was investigated and comprehensive models were deduced to describe these rela-tions. Adequate geometric and hydraulic design could achieve high levels of fish protection anddownstream passage efficiency, even for small fish, weak swimmers and riverbed/bottom orientedspecies. The results imply good transferability and accordance with field observations at largescale facilities and can provide valuable information for facility design

Keywords: Fish downstream migration, hydro power, screen, bypass, behavior, passage distribution


59



Field measurements of the attractivity of bypasses forfish-friendly trash-rack

Fatma Lemkecher ∗† 1, Laurent David 1, Dominique Courret 2, Ludovic Chatellier 1

1 Institut pprime – Universite de Poitiers – France2 Agence Francaise de la Biodiversite (AFB) – Agence Francaise de la Biodiversite – France

Fish-friendly trashracks, combining a low bar-spacing rack and bypasses, are a solutiontowards the fish downstream migration issue at hydroelectric intakes and rehabilitate the eco-logical continuity, as aimed by the European Water Framework Directive (2000). To complyto the French Environmental Code, the Hydropower plants (HPPs), located on rivers listed inlist 2 according to the article L-214-17, must ensure an adequate sediment transport and freemovement of fishes along the river. Each infrastructure has to be managed, and equipped ac-cording to the rules set by the administrative body in concertation with the owner or at leastthe operator. This study concerns inclined trashracks, which have an acute angle starting fromthe ground, to guide fishes to one of the surface bypass entrances. Well dimensioned bypassesshould allow an efficient attraction of the fishes, while limiting the discharge in the bypasses thatcause loss for hydraulic operators. In this context, a measurement campaign in a hydropowerplant on the Ariege river has been carried out to characterize the velocity profiles at differentpositions upstream of a 26◦ angle trashrack with an ADCP and the flow discharge of each of the3 bypass entrances with flowmeter measurements. The measurements show that the streamwisevelocities are quite homogeneous along the rack, without significant acceleration or deceleration,and that the tangential and normal velocities, Vt and Vn, are consistent with their theoreticalvalues. These results tend to validate the angular criteria proposed for inclined rack by Courretet Larinier [6] and studied experimentally by Raynal et al. [4] on a down-scaled model. However,it must be considered that the turbine discharge was low the day of measurement. So, these insitu measurements have to be conducted again, with a turbine discharge closed to its maximum.

Keywords: Fishfriendly trashrack, downstream migration, ADCP measurements


60



Hydropower dams threaten freshwater Chilean fish species:what dams and what species?

Anita Laborde ∗† 1, Oscar Link 1, Evelyn Habit 1

1 University of Concepcion (UdeC) – Chile

Increasing energy demand due to growing population and industrialization is exerting pres-sures on ecosystems worldwide, especially on those having available potential pertaining to thenon-conventional renewable energies NCRE (Latrubesse et al. 2017). Hydropower is the domi-nant renewable energy source, as a clean and mature technology is experiencing a developmentboom worldwide (Kelly-Richards et al., 2017), but at the same time associated longitudinalfragmentation of the physical habitat worsen the conservation status of freshwater species, chal-lenging sustainability. Connectivity between habitats can be critical to ensuring the long-termpersistence and success of fish populations (Fullerton et al., 2010). Lack of access to differenthabitats, can ultimately lead to a population decline, and a loss of biodiversity (Franklin andBartels, 2012). Loss of natural river network connectivity is considered to be one of the maincauses of the decline of freshwater ichthyofauna (Romao, 2017).Nevertheless, not all planned SHP will affect freshwater fish species. What projects will po-tentially affect species, depend on a number of attributes such as location and size, while whatspecies are potentially vulnerable to hydropower projects depends on a number of species specificattributes such as distribution and conservation status. Additionally, mitigation technologies toreduce the impact of hydropower projects on freshwater fish species are available (Noatch andSuski, 2012; Noonan et al., 2011; Kemp, 2016).In this work, we analyze Chilean Freshwater species distributed over 10 major basins of Cen-tral Chile threaten by 1124 plants (totalizing an installed capacity of 12,338 GW) planned in ahotspot of biodiversity including the Chilean ichthyogeographic province (Myers et al., 2000).The analysis consider species distribution, conservation status and richness, as well as location,size, head and turbine type of hydropower projects. Chile has 45 non-sport native species withhigh conservation value, because of its particular origin, high percentage of endemism and prim-itive characteristics (Dyer 2000), from which 66% inhabit in this zone, 74% of the fish speciesare endemic and 39% are classified as endangered.Results show that the projects located in reaches with information about species compile 45%of the exploitable potential, with 69.8% located in the Andean range, and 58.7% in reaches withlow Strahler order (≤ 3). 75.5% have installed capacities less than 20 MW and 62.3% con-sider low head dams ( 60). The latter species pertain to genera Trichomycterus, Percilia, andDiplomystes, defining a critical fish assemblage that facilitates the management of an importantpart of the cases through mitigation technologies (such as a multispecific fishway). Results arediscussed in terms of information availability and territorial planning.

Keywords: Hydropower, fragmentation, biodiversity, fishway


61



Fish swimming kinematics in a turbulent wake: to spill or notto spill?

Valentine Muhawenimana ∗† 1, Catherine Wilson 1, Joanne Cable 2

1 Cardiff School of Engineering – Queen’s Buildings, The Parade, Cardiff CF24 3Cardiff, Wales, UnitedKingdom

2 Cardiff School of Biosciences – CF10 3AX Cardiff, Wales, United Kingdom

Due to the complex nature of fish-environment interactions, the effects of altered flow condi-tions on fish habitats and behaviour, particularly near obstructions, are not yet fully understood.Many hydro-engineering structures generate three-dimensional turbulent structures that differin properties from naturally occurring ones, and are challenging to fish movement. Here, swim-ming stability and habitat usage of Nile tilapia (Oreochromis niloticus) were examined in theturbulent wake of a horizontally oriented cylinder (50 mm diameter, D) for a series of increasingcylinder Reynolds numbers (Red). Velocity statistics showed that the near wake downstreamof the cylinder within a 2D distance had higher magnitudes of longitudinal, vertical and lateralvelocity components as well as Reynolds stresses, turbulence intensity and turbulent kinetic en-ergy than the remaining wake flow field. Flow accelerating over the cylinder top and undersidegenerated two shear horizontal layers, where two coherent structures were formed due to theshear layer breakdown off the cylinder’s walls and alternating von Karman-type vortex sheddingoccurred in the wake of the cylinder. The eddy symmetry and vorticity off the cylinder’s edgeswas dependent on Red. The recorded total number of spills, defined as loss of balance, wasinversely proportional to fish length and weight, and depended on proximity to the cylinderand the flume bed. Furthermore, the frequency of spills was closely linked to the orientation ofvortices and magnitude of Reynolds stresses, suggesting that these parameters may govern theswimming stability of fishes. This information may be used to inform the design of fish-friendlyobstacles including hydraulic structures and hydro turbines in riverine and estuarine systems.

Keywords: turbulent wake, fish swimming kinematics, turbulence and fish interactions


62



Development and Tests of a 3D Fish-Tracking VideometrySystem for an Experimental Flume

Martin Detert ∗† 1, Cornelia Schutz 2, Rebekka Czerny 3

1 Laboratory of Hydraulics, Hydrology and Glaciology VAW, ETH Zurich, CH-8093 Zurich– Switzerland2 German Federal Institute of Hydrology BfG, D-56002 Koblenz– Germany

3 Federal Waterways Engineering and Research Institute BAW, D-76187 -Karlsruhe – Germany

To design effective and efficient fish passage facilities at hydropower plants, the knowledge ofswim behaviour of fish is essential. Therefore, living wild fish were investigated at different fishguidance structures in an experimental flume in a test section of 11 m length and 2.5 m widthat water depths of about 0.6 m. Besides analysis of time data and manual recordings of thefish behaviour, video recordings of the fish movements can allow more detailed analysis of fishbehaviour in different hydraulic situations. Thus, a videometry system was installed consistingof eleven synchronous cameras with overlapping views lined-up under dry conditions outsidethe flume. A 3D tracking algorithm was developed and implemented to analyse the video data.Core of the code is a motion-based multiple object tracking method, in which several objectscan be tracked in 2D pixel-frame coordinates at the same time. After undistorting and stereo-calibrating the cameras, the 2D tracks are transferred to a 3D metric-space according to theirepipolar geometry. Within this paper video data from a single experimental run of 15 min withthree fishes with lengths of 100–150 mm are analysed exemplarily. The path-time diagram gives adistinct ‘big picture’ of the fish movement, which helps to identify preferred and disliked regions.However, due to imperfect actual camera setup, a 3D view in the near field of the cameras andan automated separation of individual tracks in a group of fish remains challenging.

Keywords: fish, tracking, videometry, ethohydraulic, experimental flume


63



Performance of a fish pass for multiple species: scale modelinvestigation

Didier Bousmar ∗† 1, Xavier Rollin 2, Loic van Audenhaege 3, Estelle Courtois 4

1 Service Public de Wallonie, Hydraulic Research Laboratory (SPW) – 164 Rue de l’Abattoir, 6200Chatelet, Belgium;

2 Service Public de Wallonie, Nature and Forests Dept. (SPW) – Belgium3 AGRO - UCL – Belgium; 4 IMMC - EPL - UCL – Belgium

Artificial fish passes are often the most effective solution to restore the ecological continuity of a

dammed river. Such a pass can be built for a specifically targeted fish species, based on the existing

knowledge on its swimming capacity and behaviour. It is however preferable to look at a wider range of

possible species to optimise the benefit of building the fish pass. This implies that the fish pass should

accommodate fish with a larger range of swimming capacities and behaviours. The paper will present

results from an experimental study performed in a scale model, using different fish species.

Seven fish passes have to be upgraded on the River Meuse in Belgium, upstream of Namur. In order to

optimize and to validate the layout of these new vertical slot fish passes, a 1:5 scale model of the Riviere

Weir fish pass was built. This scale model was initially intended only for flow investigation. Taking

benefit of its existence, it was then decided to initiate an exploratory program of tests with living fish.

A first methodological objective of this study was to investigate the application of scaling laws to living

material. To respect the geometrical scale of the model, juvenile fish have indeed to be used if available.

Considering empirical relations from the literature that give swimming velocity as a function of fish size,

it could be shown that the juvenile fish swimming capacity in the model was actually lower relatively to

the adult fish swimming capacity in the prototype. Taking into account the possible bias linked to the

scaling, further objectives of this study were: (1) Estimate the capacity of different fish species to cross

successive pools of the fish pass; (2) Test their capacity to enter the fish pass from the downstream river

reach; (3) Observe their swimming behaviour in a characteristic pool.

Four fish species were used during the experiments: (1) Altantic salmon (Salmo salar); (2) Bleak (Al-

burnus alburnus); (3) Chub (Squalius cephalus); and (4) Bullhead (Cottus gobio). Altantic salmons and

chubs were farm fish; while bleaks and bullhead were captured in nature. Farm fish were juvenile, selected

so that their size approximately corresponds to adult size scaled according to the model geometrical scale.

Captured fish were mainly adults, so that the geometrical scale was no more respected.

Fish were introduced in the downstream pool of the model. Their attempts to swim the fish pass and

trajectories in the basins were observed and recorded using video cameras. The large individuals (i.e.

salmon, chubs and some bullhead) were marked with pit-tags and their movement were recorded by an-

tennas installed at several slots of the fish pass. An additional test was done with the chubs, introducing

them in the river basin, downstream of the fish pass.

Different results were collected, notably in terms of rate of crossing, duration of a typical crossing, ac-

cording to the fish species, to the fish length, and to the daylight conditions. It was observed that the

species known as good and relatively good swimmers (salmon, bleak and chub) could cross the fish pass

quite easily. Their typical trajectories, and preferred presence area were also identified. On the other

hand, the swimming capacity of the bullhead, and mainly of the small individuals, was found too low

to move fluently in the pass. Bullhead is a benthic fish. The absence of bed roughness elements in the

model jeopardised its swimming possibilities and could partly explain these poor results. Lastly, it was

also confirmed that the chub introduced in the river could enter quite easily the fish pass.

Keywords: fish pass, experimental investigation, scale model


64


Thursday 6 September, 8:45 – 10:25

Thursday 6 September

8:45 – 10:25

BC 3 – Physical Models . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Me 3 – Driftwood – part 1 . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Li 3 – Sediments: large-scale/field studies . . . . . . . . . . . . . . . . . 78

Br 3 – Flooding processes and compound channels . . . . . . . . . . . 83

65

Thursday 6 September, 8:45 – 10:25 BC 3 – Physical Models

Multiple approach for the design of the labyrinth spillway onthe Nam Teng river, Myanmar: concept design – CFD –

Physical model.

Francoise Bigillon ∗† 1, Bard Venas 2, Aslak Løvoll 2

1 Norconsult AS – Postboks 626, NO-1303 Sandvika Vestfjordgaten 4, NO-1338 Sandvika, Norway2 Norconsult AS – Norway

The paper presents the results of a project to design a labyrinth spillway on the Nam Teng (UKT)

river in Myanmar. The choice of a labyrinth spillway compared to a more conventional ogee spillway was

motivated by the hydrology (The 1000-year flood flow is 3055m3/s and the PMF is QPMF = 6800m3/s,

which are very high flood flow value due to monsoon climate in that region) and some constrains on site

topography and geology (limited width and depth to construct the weir). An alternative study on the

spillway (broad crest, ogee, labyrinth) showed that the labyrinth spillway was the best solution. The

labyrinth spillway design consisted in three steps: the concept design, a numerical model of the spillway

and a physical model of the spillway.

The concept design of the labyrinth spillway is based on design recommendations for labyrinth weirs from

Tullis (1995). The labyrinth spillway is 140 m wide and can pass the QPMF within 5.5 m water depth

over the weir crest. The flow condition at UKT were outside the range for the design criteria. To check

the concept design of the spillway at UKT, and as an aid to further improving the design, Computational

Fluid Dynamics (CFD) simulations and tests on physical model were performed.

CFD simulations were performed using ANSYS CFX (v.17.0). The weir, chute and stilling basin flows

were analysed using body fitted hexahedral meshes and the inhomogeneous Eulerian-Eulerian solver in

CFX. Upstream conditions were investigated using one-phase simulations on a tet/prism mesh resolving

both the bathymetry of the reservoir and the geometry of the approach channel. The CFD simulations

helped to improve the flow condition at the entrance and towards the labyrinth weir by altering the

approach channel. The CFD also confirmed the concept design and capacity of the labyrinth weir. Finally,

the results of CFD simulations were used to design the chute and stilling basin energy dissipation.

A model study was performed at the Department of Hydro Power Implementation (DHPI) Hydraulic

Laboratory at Paunglang, Myanmar to check the hydraulic performance of the UKT spillway and if

needed to optimize the design for better hydraulic performance. Two models were built. One model at

scale 1:50 that includes the approach channel, labyrinth weir, chute, stilling basin and first part of the

outfall channel. Test were performed for flows up to Q = 6800m3/s. Tests were also performed with

floating debris and movable bed in the outfall channel.

A second model in scale 1:30 was built that included one of the 5 bays of the labyrinth weir. The main

purpose was to investigate the need for nape aeration.

The model tests confirmed the capacity of the labyrinth weir and helped to conclude on the need for

aeration and challenge of floating debris. The model tests were also used to adjust two different transitions

in the outfall channel and to confirm the erosion protection design of the outfall channel.

The multiple approach to the spillway design has proved very useful. The concept design and CFD

simulations provided a design with need for few adjustments in the detailed design phase. The physical

model studies helped clarify complicated issues as debris flow, aeration, risk for scouring and gave a

general visual confirmation of the design.

Keywords: Labyrinth spillway, CFD, Physical model, hydraulic design


66



Scale model of a training dam using lightweight granulates

Bart Vermeulen ∗ 1, Matthijs Boersema 2, Ton Hoitink † 3, Arjan Sieben 4, Kees Sloff 5,Maarten van der Wal 5

1 University of Twente – The Netherlands2 Delta Academy – The Netherlands

3 Wageningen University (WUR) – The Netherlands4 Rijkswaterstaat – The Netherlands

5 Deltares – The Netherlands

Longitudinal training dams (LTDs) are a promising alternative for river groynes. Here wesummarize findings of a recent study focused on the along river transition from a series of rivergroynes to an LTD, where the flow divides between the fairway and the side channel betweenthe LTD and the river bank. A scale model is setup using lightweight granulates made ofpolystyrene to create conditions that are dynamically similar to a prototype situation in theRiver Waal. The key advantage of using lightweight granulates is that both the Shields numberand the Froude number are similar in the model and the prototype. A high flow and a lowflow experiment were carried out. The bedforms in the physical model have dimensions thatcorrespond to theoretical dune height predictions, and also the channel incision due to widthreduction is in accordance with expectations. The scour holes that develop near the tip of thegroynes, however, are too deep, which may relate to improper scaling of the local turbulentvortices, initiated at the groynes. The morphodynamic developments in the flow divergencezone are subtle, and are overwhelmed by the mobile bed response to the presence of groynes.Considering that the physical model over-predicts the erosion caused by groynes, this suggeststhat the LTD configuration subject to study results in a comparatively stable bed morphology.

Keywords: physical scale modelling, longitudinal training dam, polystyrene granulates, scour


67



Flow Bifurcation at a Longitudinal Training Dam: Effects onLocal Morphology

Timo de Ruijsscher ∗† 1, Suleyman Naqshband 1, Ton Hoitink 1

1 Wageningen University & Research (WUR) – Netherlands

Longitudinal training dams (LTDs) have been built over a length of 10 km in the DutchRiver Waal as an alternative to groyne fields, splitting the river in a main channel and a bank-connected side channel in the inner bend. Here, we study the physical mechanisms governingthe three-dimensional flow and its effect on local morphology at the flow divide.The characteristics of the three-dimensional flow are studied using a mobile bed physical modelof an LTD, adopting a geometrical scale factor of 60. The model is centred around a side chan-nel intake. In line with previous experiments, polystyrene granules are used as a lightweightsediment that allows to achieve dynamic similarity between the model and the prototype. AnAcoustic Doppler Velocimetry (ADV) profiler is used to monitor the flow characteristics, whereasa line laser scanner set-up is used to measure the morphological imprint of the flow near thebifurcation point. To study the dependence of the results on the sill height at the side channelintake, different forms and heights of the sill are used.The results are ongoing, but first results show striking similarities with measurements from thefield pilot in the Waal River, as well as larger sedimentation in the side channel for a uniformlow sill compared to a downstream increasing sill height. Regions of large sedimentation becomeeroded again when the discharge and the waterlevel increase, indicating that it is not likely thatthe side channel will become an inactive sediment trap.

Keywords: Flow bifurcation, Morphology, Training dam, Physical scale model, Waal River


68



Dam-break on an idealised hill side: preliminary results of aphysical model

Silvia Cordero ∗† 1, Andrea Cagninei 1, Davide Poggi 1

1 Department of Environment, Land and Infrastructure Engineering, Politecnico di Torino (DIATI,Politecnico di Torino,) – Corso Duca degli Abruzzi 24, 10129 Torino, Italy

The aim of this work is to study the propagation of dam-break waves along a hillslope. The main

reason behind this work is to design a simplified procedure to help regional and local authorities in the

evaluation of the hazard due to the presence of many small (i.e. volume less than 1Mm3 and height less

than 15m) earthen embankments within their territory. These structures are usually used for agricultural

purposes or for artificial snow production. They have no natural inflow and no valley downstream so

the propagation of the wave due to a dam-break can’t be studied as a 1D flow. Diffusion along the

direction perpendicular to the breach axis play a key role in the assessment of the potential flooded area.

The downstream slope and roughness plus the collapse dynamic are the main factors to be considered

assessing the wave front width.

Here we present a physical model build up in the Hydraulic Laboratory of the Politecnico di Torino. The

setup consists of a 3m wide and 4m long wood plane set downstream of a reservoir. After the sudden

removal of a gate the flow propagate along the plane. Another tank (3.5m x 1m x 0.3m) is set downstream

to collect the water and to reuse it. We want to recreate the water surface, to assess the shape of the

flooded area and the arrival time of the wave front. We use a video camera (Andor Zyla 5.5, sensor CMOS

2560x2160 pixel, 100 fps, lens Sigma 18-35) and we measure the water height by linking the intensity of

the pixels in the acquired images to the real water depth. A scarlet dye is uniformly mixed to the water

acting as a light absorber. The camera is set at 3m over the plane (by mean of 2 portals that allow us

to acquire all the surface in 2 different iteration or simultaneously using 2 cameras, one for the upstream

portion and one for the downstream). We can change the plane slope, the shape of the reservoir and the

breach shape.

To obtain the necessary illumination we made a ”light box” around the plane. The plane is white painted

to maximize the light reflection. The light sources are 20 10W floodlights aligned in 2 rows on the 2

sides of the plane 2m over it. They are pointed on 2 diffusers to avoid the direct reflection on the water

surface. The whole set up is set inside a black room to prevent the influence of the day light and to have

standardised environmental conditions. An air-conditioning is used to keep better work conditions for

the camera.

Based on previous statistical analysis of the small embankments in Piedmont Region, we adopted two

different kind of reservoirs: a wedge reservoir 1m x 1m x 0.2m high at the gate and a prismatic reservoirs

1m x 1m x 0.4 m. For the breach, we adopt the shape and size of a completely developed breach in an

earthen embankment in accordance with Froehlich’s model (1995).

Preliminary qualitative results are presented for the wedge reservoir and quantitative results are given

for the prismatic one in case of flat plane (slope 0◦).

Further steps will be: 1) the improvement of the lighting system; 2) the improvement of the opening

system; 3) the use of a new upstream reservoir and the introduction of a different slope between the

plane and the bottom of the tank; 4) treat different shapes of breach; 5) try various roughness on the

downstream plane to simulate the different use of soil in the territory downstream the real reservoirs.

Keywords: Dam, break, flooded area, imaging techniques


69



Experimental assessment of alluviation downstream ofHun-lock, Belgium

Catherine Swartenbroekx ∗† 1, Celine Savary 1, Didier Bousmar 1

1 Hydraulic Research Laboratory, Service public de Wallonie (SPW) – Rue de l’Abattoir 164 6200Chatelet, Belgium

To ensure a safe and efficient inland navigation, the water depth has to be sufficient in the water-

ways. For instance, the vessel draught ranges between 2.5 m and 4.5 m for ECMT class IV (1350 ton)

and Va (2000 t), respectively. Shipping channel and river alluviations should then be removed regularly

to maintain the navigation. However, the excavation process and the dredged material treatment are

expensive. A better understanding of sediment transport and siltation processes may diminish the fre-

quency of recurrent dredging.

This paper is devoted to the deposition crest in the Hun-lock area, which has to be dredged almost every

two years. A long-term solution is searched for, based on the understanding of water velocity field and

solid transport processes, to avoid the expensive dredging.

Hun movable dam is located on the Upper River Meuse, in the south of the city of Namur in Belgium,

and is made of four 22.5 m-wide sluices. Each opening is closed by a radial gate on top of which is sat

an upper flap gate. A movable hydropower station is installed in the right sluice. It is designed in the

following way: at low discharge, the gate is opened in such a way that the main discharge flows through

the turbine; when the discharge increases (above 500 m3/s), the hydropower unit is lifted to let the gate

recover the control (up to 1800 m3/s). The lock, located on the left of the dam, belongs to ECMT class

IV (1350 t, 100 m x 12 m). The deposition crest is forming at the lock downstream entrance.

The physical process is analyzed thanks to a small-scale model, built at scale 1:50 according to Froude

similarities, in the Hydraulic Research Laboratory of the Walloon administration. It stands for a 500

m-long reach of Upper Meuse, with Hun movable dam as upstream boundary. The bathymetry was

reproduced in the model as measured in the field in 2015. An upstream tank and an inlet section allow

for a homogeneous inlet flow. The incoming discharge Qm can vary between 20 l/s and 250 l/s. The

tailwater level is regulated via an outlet flap gate at the end of the channel. The discharge is measured by

means of two electromagnetic dischargemeters installed in the supply line, with an accuracy of 0.2 %. The

water level is measured in seven fixed locations with ultrasonic gauges. The velocity components were

recorded in a grid of points with an electromagnetic probe, which is located on a trolley and displaced

automatically.

Several field discharges Qp (from 250 to 1000 m3/s) and distinct dam openings (flow through the whole

dam, through two sluices or through the hydropower plant only) are tested in the present configuration.

Modifications of the downstream guard wall that separates the harbour entrance from the dam channel

are also considered, by increasing the wall length or by perforating ports in the wall. Building groynes in

the right side of the river is analysed too. Finally, flushing water through the lock toward the alluviations

is tested.

The velocity field analysis explains the alluviation processes. They are due to the localisation of the lock

in an enlarged area of the Upper Meuse and in a meander intrados, where the flow velocity is decreasing.

Recirculation zones and vortices are highlighted. Finally, the comparison shows that none of the tested

solutions is completely convincing according to 4 criterions: (1) ability to decrease the deposition crest,

(2) navigation requirements, (3) safety in case of high-stage discharges, and (4) acceptable cost.

Keywords: velocity field, deposition crest, alluviation, sediment transport, mobile dam, lock, wa-

terways


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Thursday 6 September, 8:45 – 10:25 Me 3 – Driftwood – part 1

Defining and characterizing wood-laden flows in rivers usinghome videos

Virginia Ruiz-Villanueva ∗† 1, Livia Burkli 1, Bruno Mazzorana 2, Luca Mao 3, DiegoRavazzolo 2, Pablo Iribarren 2, Ellen Wohl 4, Markus Stoffel 1

1 Institute for Environmental Sciences, University of Geneva – Switzerland;2 Institute of Earth Sciences, Universidad Austral de Chile, Valdivia – Chile;

3 Pontificia Universidad Catolica de Chile – Chile;4 Department of Geosciences, Colorado State University – United States

Various types of flows involving water and sediments occur in mountain areas, including floods with

or without intensive bedload transport, hyperconcentrated flows, mudflows, and debris flows. However,

rivers do not only carry clear water and sediments. In forested basins, large amounts of organic material

(i.e., wood) can be transported as well. The classical criteria used to distinguish between flows may vary,

but usually consider inorganic sediment as the only component of the solid fraction and thus neglect

the role of organic material. However, the physics of wood transport differs significantly from that of

sediment transport because of differences in shape, density and size of the mobile constituents. Therefore,

specific characteristics can be expected when flows carry significant amounts of organic material, but these

characteristics are not yet well understood. An important limitation in defining organic sediment-laden

flows (defined here as wood-laden flows) is the lack of direct observations of flows in which organic material

is significant. This work aims to shed light on this by collecting data from direct observations of wood-

laden flows from home videos and by extracting quantitative information for a better characterization of

flows in forested rivers.

Home videos that are available online were collected by using technical keywords related to floods, flash

floods and wood loads in English, German, Spanish, French, and Japanese. More than 45 home videos

were retrieved showing flood events occurred in several regions of the world with notable amount of wood

and 28 of them were selected for further analyses after an initial screening. Additionally, watershed

and stream characteristics were also collected. Results show that, in general, wood-laden flows were

recorded in small- to medium-sized catchments, and confined to relatively steep single thread channels.

One important common characteristic is the flashy response, with a very fast (i.e., few minutes) increase

in water level, from nearly dry channels to overbank flooding.

The post-processing of these videos provided data to characterize the flows and to redefine wood transport

regimes. The classical description of wood transport in rivers considers congested, semi- and uncongested

transport. Based on our observations, we add a new regime called hypercongested.

During an uncongested or semicongested wood-laden flow, a point is reached at which the logs begin

to interact with each other. As the proportion of wood increases, another transition zone (or phase) is

crossed during the congested flow regime. Hypercongested flow starts as soon as wood material increases

to the point where the flow is no longer partially liquefied (i.e. ,when the dry front is formed), although

such a mixture might be saturated and pore water might be trapped to some degree (depending on

sorting) in the framework of logs. Depending on the shear strength and the dynamic particle-support

mechanisms operating, very large particles can be transported, to such a degree that even those exceeding

the floating competence of the flow can be rolled along by the flow. In that case, the bulk behavior is

governed by a decreasing water content which promotes the formation of interparticle forces such as

friction and collisions. Usually, the hypercongested flow regime is formed first, followed by congested

and/or uncongested flow regimes. In all cases, we observe the peak of the wood flow before the peak of

the flood hydrograph.

The observations provided by the home videos thus allowed us to propose a novel classification based on


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the properties and characteristics of the flows, formatted as a ternary diagram with several boundaries

defining the transition from clear water to hypercongested wood debris flows, according to the composition

of the mixture (sediment, wood, and water).

In addition, four hypotheses are presented about the triggering of wood-laden flows: (i) a large amount of

wood within the channel is available for transport before the flashy hydrograph; (ii) a wood jam breaches,

in which a large wood jam collapses and delivers a lot of wood; (iii) an episodic input of wood from a

landslide, debris flow, or a tributary in flood before the arrival of the flood in the main stem; and (iv) the

presence of a narrow river section upstream in the main channel, in which the wood might be retained,

and suddenly released during the flood.

These results represent a valuable contribution to a better understanding of flow phenomena in forested

river basins. Moreover, properly identifying the flows that are likely to occur in one watershed allows

designing better management strategies.

Keywords: Flow dynamics, instream wood, forested basins, floods

72


Large wood recruitment and mobility in steep mountainstreams of contrast European landscapes

Tomas Galia ∗† 1, Vaclav skarpich 1, Radek Tichavsky 1

1 University of Ostrava (Ostrava university) – Dvorakova 7, Ostrava, 701 03, Czech Republic

Instream large wood (LW) is an important component of stream habitat heterogeneity,but several aspects of its recruitment, transport and deposition in fluvial systems includingsteep channels (here defined as channels with bed gradients S > 0.04) are still not compre-hensively understood. We present a comparative study of LW mobility in two steep channels(0.06 < S < 0.20) located in contrast European landscapes during major hydro-geomorphicevents (assumed 10-20y recurrence interval). We investigated a headwater perennial streamdraining densely forested Central European medium-high mountain relief (Klepacsky, HrubyJesenık Mts, Czech Republic; A ≤ 2.5km2) and an ephemeral Mediterranean channel (Sfakianogorge, Crete, Greece; A ≤ 50km2) with notably lower production of biomass due to relativelydry climate. Both studied hydro-geomorphic events (Klepacsky in May 2010, Sfakiano Gorgein December 2000) were partially accompanied by debris-flood or debris-flow character of sed-iment transport including significant content of LW. The minimal estimations of transportedLW volume were 71.3 m3 along the 1.70 km long studied reach of Klepacsky and 49.4 m3 alongthe 4.05 km long studied reach of the Sfakiano gorge. The total measured wood loads (includ-ing autochtonous LW pieces) in studied reaches were 123 m3 in Klepacsky and 132 m3 in theSfakiano gorge. Despite completely different characters of hydrologic regimes, riparian zones andvalley confinement settings, living trees in the valley floor played crucial role in wood depositionand development of large allochtonous jams in both environments. Twelve partially damagedcheck dams in Klepacsky were additional important barriers for downstream wood transport,when ca. 25% of the total LW volume was stored in relation to these check dam constructions.The trees living in the valley floor were assumed to be the main source of LW in the studiedMediterranean channel (by individual tree throws or broken branches of sufficient LW dimen-sions), whereas long-term LW recruitment from very steep hillslopes or rock cliffs was quitenegligible. On the other hand, a few previous windstorms between the years of 2000 and 2010in Klepacsky caused notable delivery of LW pieces from adjacent hillslopes and LW recruitmentby bank erosion occurred only in some spatially-limited locations of semi-confined valley parts.

Keywords: large wood, wood transport, wood jams, mountain stream


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Using tree-rings to determine large wood residence time andtransport pulses in a gravel-bed river

Maxime Boivin ∗† 1, Thomas Buffin-Belanger 2,3, Dominique Arseneault 2,3

1 Univ. Quebec, Chicoutimi (UQAC) – 555, bd de l’Universite, Chicoutimi, Quebec G7H 2B1 – Canada;2 Univ. Quebec, Rimouski (UQAR) – 300 Allee des Ursulines, Rimouski, Quebec G5L 3A1, Canada;

3 Centre d’Etudes Nordiques (CEN) – Canada

Pioneering works on large wood (LW) in rivers have described historical wood accumulations in North

American rivers at the time of European colonization. The Great Raft of the Red River for example,

was an enormous wood accumulation that was more than 300 km with a long residence time during the

19th century (McCall, 1988). In modern times, such large rafts are unusual because of river management

(Wohl, 2014).

The gravel-bed rivers of the Gaspe Peninsula, Quebec (Canada), recruit and transport vast quantities

of large wood during flood events. The rapid rate of channels shifting due to high-energy flows and

non-cohesive banks allow the recruitment of large quantities of wood that in turn greatly influence river

dynamics. The delta of the Saint-Jean River (SJR) has accumulated wood since 1960, creating frequent

avulsions, leading to a wood raft of more than 3 km in length as of February 2015. The exceptional

amount of wood found in the raft of the SJR is unusual but natural (Boivin et al. 2015).

Tree-ring analyses have been used extensively to document hydrogeomorphological dynamics (Boucher

et al. 2009). Here, for the first time, tree-ring analysis from wood trapped in the SJR raft allows a

unique opportunity to estimate residence time of large wood in a river corridor and to ascertain the role

of environmental factors in large wood production cycle in a cold region environment. Specific objectives

include : 1) to determine the temporal pattern of wood recruitment; 2) to examine the role of fluvial ice

conditions in the transport pulses; 3) to quantify the large wood residence time and; 4) to characterize

the cycle of large raft formation in the delta of SJR.

Managers of the SJR carried out a vast dismantling operation to remove more than 1200 meters of the large

raft in the southern channel of SJR delta in February 2015. This offered the opportunity to collect large

wood for tree-ring analysis along the whole length of the raft. In total, 319 pieces of Thuja occidentalis

were extracted at, on average, every 3 linear meters of the southern channel. The wood recruitment date

was determined by crossdating tree ring width patterns to the calendar year (Gennaretti et al. 2014),

using the master chronology (1404–1982 AD) developed by Cook (1994) along the nearby Sainte-Anne

River. The estimation of residence time (transit from the watershed to the delta) is made possible by

comparing the year of recruitment to the year of accumulation in the delta. Analysis of aerial photos

(1993-2004), satellite images (1999-2014) and five years surveys (2010 to 2014) allowed to know the exact

year of each LW arrival within the delta.

Analysis of aerial and satellite images allowed knowing the volume of large wood brought in the delta

since 1993. A large variability of LW fluxes is observed from one year to another. For example, the flood

of December 2010 brought nearly 200 linear meters of additional wood in the Saint-Jean Delta compared

to the flood of 2007 when no LW was added to the raft. The dendrochronological data used to establish

the age of the trees produced by the watershed and established transit time between its recruitment in

the watershed and its arrival in the raft. These data and analysis show the hydro-climatic conditions for

the transport and recruitment of wood for the period 1993 to 2014.The results also showed that there

are three types of LW flood related to wood dynamics: 1) an erosive flood that produces a large amount

of wood in river; 2) a mobilizing flood that carries large quantities of wood and; 3) a flood mix that

produces and transports large quantities of wood.

Dendrochronological crossdating will allow to determine whether there are key years or cycles in the

∗Speaker†Corresponding author: maxime2 [email protected]

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production of LW in the SJR. Then, because we know the arrival year of each LW sampled, it will be

possible to determine their residence time in the river system. The residence time will also be analyzed

according to hydro-climatic conditions and fluvial ice conditions that prevailed during the period of

residence in the system. These two elements combined with existing data on the volume of LW recruitment

and transport, will allow the development of a LW budget (production, transport and accumulation) at

the scale of the watershed. This is a unique analysis that can be realized through the combination of

dendrochronology, geomorphology and hydroclimatology. In most rivers, transported LW are evacuated

from the river system and it is very difficult to estimate residence time at the watershed scale. With

the increase in volumes of wood produced and transported in the river, our results confirm that water

management’s agency must integrate this dynamic into the rivers of Eastern Quebec, Canada.

Keywords: large wood in river, dendrochronology, residence time, wood transport, riparian ecosys-

tem, large raft, large raft dismantling.

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The influence of large wood and rootwads on flow patterns andbed morphology in a moving bed channel

Su-Chin Chen 1, Min-Chih Liang ∗ 1, Samkele Tfwala † 1

1 Department of Soil and Water Conservation, National Chung Hsing University, 145 Xingda Road,402, Taichung – Taiwan

Studying large wood in river channels can help gain insight on their form and processes.Over the preceding decade, laboratory and field experiments have been used to explain wooddynamics, flow patterns and sediment transport. Moreover, field experiments are sparse, whilelaboratory experiments have focused mostly on fixed bed to capture their entrainment. Toenhance our scientific understanding on logs of different morphology, this study designed anexperimental flume to investigate the effects of log presence on flow and bed topography in amoving bed channel. Two log configurations were used, with and without rootwad. Wood pieceshad a length of 0.2 m, diameter 0.05 m and a density of approximately 760 kg/m3. Rootwadwere simulated by joining 0.06 m wood pieces, having a diameter of 0.02 m to the base of the logpieces at an angle of 30◦. The experiments were carried out in a 4 m long flume, 0.6 m widthand 0.6 m deep, and having a slope of 0.001. The experimental bed zone was paved with uniformsand, d50 = 0.750 mm, of 0.1 m thickness. Flow in the channel was set such that it was below thecritical flow for wood entrainment, and it ranged between 0.0015 to 0.005 m3/s. Three differentorientations of the log were considered, namely parallel, oblique and transverse to flow. Bedevolution was monitored using a camera and a laser mounted on a moving motor frame. Thisresearch shows that log orientation and the presence of rootwad dictate bed elevation changesand stability of single wood pieces. In addition, the contrast of morphological changes caused bythe presence of abundant wood in a moving bed is crucial in determining large wood appropriatefor river restoration. Our study provokes fascinating questions for future investigations.

Keywords: large wood, moving bed, rootwad, bed morphology


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Effects of a large woody debris accumulation on channel-bedmorphology during flood events

Gabriel Spreitzer ∗† 1, Heide Friedrich 1, Jon Tunnicliffe 2

1 The University of Auckland (Department of Civil and Environmental Engineering) – New Zealand2 The University of Auckland (School of Environment) – New Zealand

New Zealand is one of many countries dealing with offsite impacts of forest harvesting, inparticular, accumulations of slash and large woody debris (LWD) that develop in steep gradientriver systems. These debris dams can impact rivers and adjacent corridors by diverting flowsto enhance bank erosion, blocking culverts and creating high-water conditions at critical bridgesites. While smaller, natural wood accumulations, may enhance the diversity of riverine andhabitat, the large and transient blockages introduced by slash accumulations can cause deleteri-ous effects to stream biota. Interaction processes of bedload and vegetation are presently poorlyunderstood and still represent a big gap in research. In this project we focus on the interactionof biotic (LWD) and abiotic (sediment) factors, relevant for hydraulic flow characteristics duringflood events. We are using a novel experimental setup in the Water Engineering Laboratory atthe University of Auckland to study LWD accumulations at a narrow river cross-section. Wemonitor resulting changes in hydraulic conditions and assess the effects on bedload transportprocesses, and thus potential morphodynamic changes in the river channel. The experimentstake place in a 6 m long, 1.5 m wide and 1 m deep, glass-sided flume with sinuous channelcourse. We use Structure from Motion (SfM) photogrammetry as an imaging method to cap-ture LWD and sediment interaction processes. Sediment quantities and changes in channel-bedmorphology (aggradation and degradation) upstream and downstream of a critical cross sectionare evaluated, together with resulting backwater effects and hydraulic flow conditions for floodevents. Our results show that bedload transport processes upstream of the LWD accumulationwere less than expected, but consistent with the backwater effect energy drop. The gainedknowledge of this study will inform New Zealand’s freshwater and forestry management, andexpand our understanding of flow-sediment-wood interaction processes in river systems.

Keywords: Large Woody Debris (LWD), Wood, sediment, flow interaction, Organic debris accu-

mulation, Hydraulic flume experiment, Structure from Motion (SfM) in the laboratory


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Thursday 6 September, 8:45 – 10:25 Li 3 – Sediments: large-scale/field studies

Phenomenology of meandering of a straight river

Sk Zeeshan Ali ∗† 1, Subhasish Dey 1

1 Indian Institute of Technology – Kharagpur - 721302 – India

Meandering rivers are ubiquitous in earth-like planetary surfaces including Moon, Mercury,Io, Venus, Titan and Mars. Since past, numerous attempts were made to probe the cause ofmeandering of a straight river. Several concepts including earth’s revolution (Einstein 1926),riverbed instability (Friedkin 1945), helicoidal flow (Tanner 1960), excess flow energy (Yang1971) and macro-turbulent eddies (Yalin 1977) were proposed so far. Despite these concepts,the exact mechanism of the meandering of a straight river remains a vexing phenomenon.Lane (1957) proposed that for nearly straight to meandering rivers, the longitudinal riverbedslope S expressed as a function of flow discharge Q is in the form of S = aQb, where a and bare the empirical coefficient and exponent, respectively. Then, Henderson (1963) introduced theeffects of sediment grain size to refine Lane’s (1957) empirical relation. However, such relation-ships exclusively stand on empirical foundation and thus, they are dimensionally inhomogeneousinviting uncertainties. Interestingly, Yalin (1977) introduced the concept of macro-turbulent ed-dies to explain the meandering of a straight river. He argued that the longitudinal length scaleof macro-turbulent eddies approximately equals the longitudinal length of alternate bars in astraight river. He considered the length scale of the macro-turbulent eddies as six times the riverwidth. Although this concept provided a qualitative idea of the meandering of a straight river,a precise physical mechanism and a quantification of this phenomenon remains still undone.In this study, at first, we analyse the linear stability of a straight river. We find that the nat-ural perturbation modes maintain an equilibrium state by confining themselves to a thresholdwavenumber band. The effects of flow regimes, aspect ratio, relative roughness number andShields number on the wavenumber band are studied. Then, we present a phenomenologicalconcept to probe the initiation of meandering of a straight river, which is governed by thecounter-rotational motion of neighbouring macro-turbulent eddies in succession to create theprocesses of alternating erosion and deposition of sediment grains of the riverbed. This con-cept is deemed to have adequately explained by a mathematical framework stemming from thephenomenology of turbulent energy cascade (Frisch 1995) to obtain a quantitative insight. It isrevealed that at the initiation of meandering of a river, the longitudinal riverbed slope obeys auniversal scaling law with the river width, flow discharge and sediment grain size forming theriverbed. This universal scaling law is validated by the experimental data obtained from thenatural and model rivers.

Keywords: Fluvial hydraulics, river meandering, sediment transport


78



Determining the dynamics of coarse bedload transport usingpassive indirect monitoring: time-dependent variability at event

to inter-annual scales

Peter Downs ∗† 1, Philip Soar 2

1 University of Plymouth – School of Geography, Earth and Environmental Sciences – Drake CircusPlymouth PL4 8AA, UK – United Kingdom

2 University of Portsmouth – Department of Geography University of Portsmouth Portsmouth, PO13HE, UK – United Kingdom

The dynamics of coarse bedload transport in rivers is governed by multiple hierarchical fac-tors including catchment-scale controls on sediment production, annually variable hydroclimaticdriving of segment-scale sediment supply, and reach-scale factors related to the interaction ofhydraulic forces with channel morphology and antecedent conditions. Whereas research intocatchment-scale controls on sediment connectivity is benefitting from terrain imaging at highspatial resolutions, sensors for indirect passive recording of coarse bedload transport offer thecomplementary prospect of exploring time dependencies related to hydroclimatic and channel-scale controls at resolutions previously possible only at select locations with extensive and per-manent bedload monitoring infrastructure.For the flashy River Avon (Devon, UK), five-minute coarse (i.e., ≥10 mm) bedload frequencydata collected using seismic impact plates inherently records the instantaneous variability ofbedload transport intensity, patterns of event-scale hysteresis and selective path transport, andthe influence of inter-event supply variations (Downs et al., 2016). Further exploration of the rel-ative role of supply and transport limiting factors requires that bedload impacts are convertedinto section-averaged estimated sediment loads. We achieve this using a probabilistic modelthat combines calculated bedload transport potential with the recorded impacts to provide highresolution, location-specific estimates of bedload that are autogenically moderated for sedimentsupply and thus less liable to over-prediction (Soar and Downs, 2017).Converting a five-year record of impacts into loads illustrates the combined influence of hydro-climatic drivers and sedimentological structures on bedload at the inter-annual scale. Despitehighly variable water years, the results indicate the consistent dominance of ‘bar-building flows’as the peak efficiency for coarse bedload transport, the relative ineffectiveness of bankfull flows,and the existence of annual sediment rating curves that combine both supply and transport lim-iting phases. The latter result suggests that sediment transport forecasting is sensitive to bothflow year type and antecedent conditions that govern the availability of sediment supply. Dataat high temporal resolution thus emphasize that coarse bedload transport is time-dependent atscales that vary from seconds to years, even in this relatively ‘sediment rich’ setting. Betterunderstanding of time-dependent bedload behaviour complements advances in catchment- andchannel-scale investigations and has implications for striving towards sustainable solutions inriver management.

Keywords: coarse bedload transport, seismic impact plates, fluvial geomorphology, time, dependent

behaviour, uncertainty, river management


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Bar dynamics and sediment transport pulses in gravel-bedchannels

Blaise Dhont ∗† 1, Christophe Ancey 1, Patricio Bohorquez 2

1 Ecole Polytechnique Federale de Lausanne – EPFL/ENAC/IIC/LHE station 18 Ecublens CH 1015Lausanne – Switzerland

2 University of Jaen – Campus Las Lagunillas, s/n. Edificio Rectorado (B1) 23071. Jaen – Spain

Mountain rivers exhibit sediment transport rate fluctuations that often cover more than twoorders of magnitude, which make their prediction very challenging. Bedform migration is oftencited as the key process that causes giant fluctuations in the sediment transport rate.To quantify the effect of bedform migration on transport rate, we ran laboratory experimentsin a 16-m long 60-cm wide flume with well-sorted gravel bed. At the flume inlet, the waterdischarge and the particle flux were kept constant (they were selected such that bed equilibriumshould be reached quickly in the flume). Experiments were conducted over long times (typically> 500 h). Sediment transport rate was monitored at the flume outlet using accelerometers (ameasurement system that was close to geophones used in many field studies). Bed topographywas scanned at high spatial resolution using laser sheets. Water depth was measured usingultrasonic probes mounted on an automated rolling carriage.We observed that, under steady state experimental conditions, bed morphology played a keypart in the generation of bedload transport fluctuations. The bars migrated downstream in-termittently, producing the most important pulses. When the bar position was stable for afew hours, additional pulses resulted from sediment transfer from pool to pool, in the form ofsediment waves (bedload sheets). Thus, in our experiments, alternate bars formed a two-entitysystem (bar + pool) with two distinctive functions: the bars contributed to fix and stabilize thebed whereas the pools were the preferential zones of short-term storage and transfer of sediment.Our study sheds new light on how the dynamics of alternate bars drive sediment transport andcontrol the frequency and amplitude of sediment pulses in gravel-bed channels.

Keywords: bedload transport, flume experiment, geophone, laser scanning, alternate bed, transport

rate fluctuations


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Impact of flow variability and sediment characteristics onchannel width evolution

Andres Vargas-Luna ∗ 1,2, Alessandra Crosato 2,3, Protogene Byishimo 2, WimUijttewaal † 2

1 Pontificia Universidad Javeriana – Colombia2 Delft University of Technology – Netherlands

3 Unesco-IHE – Netherlands

Alluvial rivers are shaped by sequences of water flows excavating their channels. Observa-tions show that besides the magnitude, also the frequency and duration of streamflow oscillationsmight be important for the river channel formation. In addition, the river morphology appearsinfluenced also by both size and degree of uniformity of the sediment. Nevertheless, many mor-phodynamic studies still represent the flow regime with a single value of the discharge, oftencorresponding to the bankfull condition, and the sediment with its median grain size. Thiswork investigates the effects of streamflow variability and sediment characteristics on channelwidth formation, analysing the evolution of experimental streams with different sediments anddischarge hydrographs. Results show that the formative condition of the channel width is notthe geometric bankfull flow but a rather frequent peak flow. Remarkably different channelconfigurations arise from different sediment characteristics in the laboratory, where sedimentnon-uniformity produces more stable banks.

Keywords: River morphodynamics, channel width, streamflow variability, bankfull discharge, sedi-

ment gradation, laboratory experiments


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Development of a method for suspended sediment transportmonitoring by means of ADCP measurements

Rui Aleixo ∗† 1, Massimo Guerrero 1, Nils Ruther 2, Siri Stokseth 3

1 University of Bologna (UNIBO) – Italy2 Norwegian University of Science and Technology (NTNU) – Norway

3 Statkraft AS – Norway

Monitoring stations in rivers and water courses are an important mean to obtain importantdata about the different variables that play a role in the hydrodynamics and ecological processes.One of these variables is the suspended sediment transport. Knowing how much sediment istransported in suspension can be useful for example, to estimate the time-life span of a damreservoir.Measurements of suspended sediment transport are usually made by taking samples of waterfrom the river and, after analysis, determine what is the amount of sediments transported in theriver. Although simple, this method usually requires human intervention, the preparation of anexperimental campaign and the displacement of means to the field. Recently some methods torelate sound attenuation with the suspended sediment transport have been presented. A methodto determine the suspended sediment concentration as a result of backscatter measurements isapplied to the data from a field monitoring station in Kokel, using a side-looking ADCP in-stalled on an almost vertical bank of the Devoll river in Albania. This method allows using theADCP to perform simultaneous measurements of both suspended sediment concentration andflow velocity, thus contributing for a better understanding of the physical processes of the river.The aforementioned method relies on the general sonar equation and on the determination ofthe ratio between the attenuation and the backscatter term. This ratio is a function of the soundfrequency and of the sediments properties. On the other hand, this ratio can be related with thesediment concentration in the fluid by means of a calibration function. This calibration func-tion depends weakly on the sediment physical properties and on the particle size distribution.However, for better accuracy, the calibration curve should be adapted to the typical sedimentstransported by the river. A calibration curve can be obtained with sediments samples takenfrom the river or by adjusting an existing curve fitted to the same type of sediments. This paperpresents the field data coming from the Kokel monitoring station and its processing algorithmto determine the suspended sediment concentration. Emphasis is given to the calibration lawobtained by samples of sediments taken from the Devoll river, and a sensitivity analysis is made.The limitations of this method are presented and its advantages and disadvantages are discussed.Finally results for the suspended sediment transport and velocity profiles are presented in a formof time series allowing identifying different hydrological events.

Keywords: Acoustic techniques, ADCP, Backscatter, Suspended Sediment Concentration, Field

Measurements


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Thursday 6 September, 8:45 – 10:25 Br 3 – Flooding processes and compound channels

Influence of floodplain and riparian vegetation in the conveyanceand structure of turbulent flow at compound channels

Joao Fernandes ∗† 1, Joao Leal 2, Antonio Cardoso 3

1 National Laboratory for Civil Engineering (LNEC) – Av. do Brasil, 101, Lisboa, 1700-066 – Portugal;2 Faculty of Engineering and Science, Universitetet i Agder (UiA) – Norway;3 Instituto Superior Tecnico, Universidade de Lisboa (IST/UL) – Portugal

During floods, many rivers assume a compound channel configuration and important interactions

between the flows in the main channel and in the floodplains may occur. Additionally, shallow vegetation

in the floodplain and riparian vegetation at the interface between main channel and the floodplain are

commonly observed increasing the complexity of the flow structure with impact in the discharge con-

veyance.

The present study aims at understanding the changes in the channel conveyance and in the turbulent flow

structure due to the presence of both submerged vegetation in the floodplains and riparian vegetation.

An experimental campaign was carried out comprising uniform compound channels flows (i) without any

kind of vegetation, (ii) with synthetic grass in the floodplains, (iii) with synthetic grass in the floodplains

and rods in the interface between main channel and the floodplain and (iv) with synthetic grass in the

floodplains and artificial shrubs in the interface between main channel and the floodplain. The experi-

ments were carried out in a 10 m long and 2 m wide compound channel. The symmetrical cross section

is composed of a trapezoidal main channel (0.1 m bank full height, 0.4 m bottom width, 0.6 m bank full

width, with a side slope of 45◦) and two lateral floodplains (0.7 m wide each). The channel is made of

polished concrete and has a bottom slope of 0.0011 m/m.

The vegetated floodplains were obtained the bottom of these subsections with 5 mm high synthetic grass.

From preliminary single channel experiments, Manning-Strickler coefficient, n, equal to 0.0092 m-1/3s,

for the polished concrete, and equal to 0.0172 m-1/3s, for the synthetic grass, were obtained.

The riparian vegetation comprises two different types of vertical elements. The first one consists of rigid,

partly-submerged elements without foliage, namely, 6 mm diameter and 45 mm high vertical rods. The

second type differs from the first one, as the elements present a highly dense foliage crown with a spher-

ical shape located radially around the centre on top of the vertical rods. The crown diameter is 90 mm.

Despite the flexibility of the branches of the vegetation elements with foliage, the shape of the foliage re-

mained practically unchanged during the tests. The vegetation elements with foliage have approximately

6 to 8 branches.cm–3, which corresponds to a high degree of ramification.

Three water depths were tested for each configuration. Accurate acoustic Doppler velocimetry was used

to evaluate the 3d velocity field and the turbulence structures.

The channel conveyance is reduced by the presence of the synthetic grass in the floodplain. That re-

duction is due not only to floodplains conveyance reduction but also due to the reduction on the main

channel conveyance. The riparian vegetation also affects the channel conveyance, but the reduction is

almost only due to the reduction of the floodplain conveyance.

Besides the reduction of the compound channel conveyance due to the increase of flow resistance, the

floodplains vegetation has a limited influence on the cross sectional distribution of the streamwise velocity,

turbulence intensities and lateral shear stress. On the contrary, riparian vegetation was found to strongly

affect these distributions blocking the lateral spreading of the lateral shear layer. It was found that the

effects of the vegetation in the flow structure are enhanced by the foliage of the vegetation elements.

The streamwise velocity patterns for flow cases without riparian vegetation are similar. An increase of the

velocity gradient between the main channel and the floodplain flows is observed for compound channels

with vegetated floodplains. This increase in the velocity gradient results in the increase of the lateral


83



shear stress. In both cases, with and without vegetation in the floodplains, increasing the relative depth

leads to the reduction of the velocity gradient.

When compared with the case without riparian vegetation, the presence of both rods and shrubs in the

interface between the main channel and the floodplain results in a different streamwise velocity pattern.

In the main channel, the maximum velocity region moves towards the bottom. The influence of the

shrubs is observed in whole main channel.

Keywords: Compound channels, flood, vegetation, floodplain

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Drag determination of an array of square cylinders subjected toshear flow in a compound channel

Miltiadis Gymnopoulos ∗† 1, Panayotis Prinos 2, Elsa Alves 3, Rui Ferreira 1

1 Instituto Superior Tecnico – Department of Computer Science and Engineering, Instituto SuperiorTecnico, laboratory, pt – Av. Rovisco Pais 1049-001 Lisboa – Portugal

2 Aristotle University of Thessaloniki – Hydraulics Laboratory, Department of Civil Engineering –54124 Thessaloniki – Greece

3 Laboratorio Nacional de Engenharia Civil (LNEC) – Av. do Brasil, 101, 1700-066 Lisboa – Portugal

Overbank flow in rivers threatens integrity of built elements located in the floodplain. Ele-ments of infrastructure close to the interface between main channel and floodplain are subjectedto complex hydrodynamic actions resulting from the obstruction of the shear flow that developsin that interface. In the current paper, the drag forces and the drag coefficient of building-likestructures positioned in the interface are investigated. The experimental setup in LaboratorioNacional de Engenharia Civil (LNEC) involves the placement of an array of square cylinderson the floodplain of a straight compound channel, next to the interface with the main chan-nel. Three-component instantaneous-velocity recordings were performed by means of AcousticDoppler Velocimetry (ADV) within the boundaries of a considered fluid-control volume encom-passing the array, while uniform-flow conditions were established in the channel. The equationof momentum conservation was applied in its integral form in the fluid control-volume towardsestimation of the time-averaged drag force at a certain elevation from the floodplain. The dragcoefficient is estimated accounting for the typical shear layer at the main-channel/floodplaininterface and is compared with coefficients strictly valid for isolated cylinders.

Keywords: array, square cylinder, drag, shear flow, compound channel


85



An analytical solution for non-uniform flow in compoundchannels

Kamalini Devi ∗† 1, Bhabani-Shankar Das 1, Jnana-Ranjan Khuntia 1, Kishanjit K.Khatua 1

1 Civil Engineering Department, NIT Rourkela, Odisha, 769008 – India

The present work investigates the analysis of depth-averaged velocity and boundary shearstress distribution in compound channels with non-uniform flow condition. A quasi two-dimensionalmodel is proposed to assess the flow variables by accounting the physical processes that are spe-cific to non-uniform flow. For analyzing the flow behavior, experimental data sets concerningcompound channels with narrowing and enlarging floodplains of previous investigators are con-sidered. The model accounts the influence of momentum transfer on the flow variables throughadditional shear stresses that are developed in non-uniform flow. Three types of effective stressesproduced by molecular viscosity, turbulent and dispersion on the vertical planes are discussed.An analytical solution to the model is presented. Terms associated with the effective stressesare investigated relating them to the geometric and hydraulic parameters. The significance oflateral variation of energy slope is further investigated. For both homogenous and heterogeneousnon-prismatic channels, the approach is examined to predict the flow variables with reasonableaccuracy.

Keywords: dispersion, transverse convection, main channel, flood plain, shear layer region, non

uniform flow


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An analytical solution for flow estimation of a meanderingcompound channel

Arpan Pradhan ∗† 1, Kishanjit K. Khatua 1

1 National Institute of Technology, Rourkela (NITR) – Rourkela Odisha, 769008 –India

An analytical model is proposed to determine the discharge capacity in a meandering com-pound channel. The channel cross-section is divided into four sub-sections, such as the lowermain channel, the floodplain within the meander belt and the two outer floodplains. Momentumtransfer in-between these four subsections is taken into consideration in the analytical model.The model basically determines the force balance of each individual subsection to predict itsmean velocity and thereby the sub-sectional discharge. The paper suggests a non-dimensionalparameter, α T, which is the momentum transfer coefficient, that is determined to be uniquefor each individual channel. The paper deals with the calibration of this parameter for bothlarge-scale and small-scale datasets.

Keywords: meandering channel, momentum transfer, discharge estimation, force balance


87



Discharge and location dependency of calibrated main channelroughness: case study on the River Waal

Boyan Domhof ∗ 1,2, Koen Berends 1,2, Jord Warmink † 1, Aukje Spruyt 2, SuzanneHulscher 1

1 University of Twente, Department of Marine and Fluvial Systems – Netherlands2 Deltares – Netherlands

To accurately predict water levels, river models require an appropriate description of thehydraulic roughness. The bed roughness increases as river dunes grow with increasing dischargeand the roughness depends on differences in channel width, bed level and bed sediment. There-fore, we hypothesize that the calibrated main channel roughness coefficient is most sensitive tothe discharge and location in longitudinal direction of the river. The roughness is determined bycalibrating the Manning coefficient of the main channel in a 1D hydrodynamic model. The RiverWaal in the Netherlands is used as a case study. Results show that the calibrated roughness ismainly sensitive to discharge. Especially the transition from bankfull to flood stage and effectsof floodplain compartmentation are important features to consider in the calibration as theseproduce more accurate water level predictions. Moreover, the downstream boundary conditionalso has a large effect on the calibrated roughness values near the boundary.

Keywords: roughness, calibration, dependence, predictions, Waal


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10:55 – 12:35

BC 4 – Experimental hydrodynamics – part 1 . . . . . . . . . . . . . . 90

Me 4 – Driftwood – part 2 . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Li 4 – Bedform and sediment transport . . . . . . . . . . . . . . . . . . 102

Br 4 – Management of hydrological extremes . . . . . . . . . . . . . . 107

89

Thursday 6 September, 10:55 – 12:35 BC 4 – Experimental hydrodynamics – part 1

Velocity field and drag force measurements of a cube and ahemisphere mounted on an artificial bed surface roughness

Paride Nardone ∗† 1, Katinka Koll 1

1 Leichtweiß-Institut fur Wasserbau, TU Braunschweig – LWI fur Wasserbau Beethovenstr. 51a, 38106Braunschweig, Germany

Quantification of the resistance in complex roughness situations, when both bed surface andform roughnesses contribute to the total resistance, as well as partitioning of the two contri-butions is still unsolved. Studies about form resistance of single elements focused on obstaclesmounted on smooth bed surfaces, and only few considered a rough bed surface. In order todefine an approach for shear stress partitioning in open channel flows, the effect of flow condi-tions, the geometrical characteristics of the obstacle, and the effect of the bed surface need tobe studied. This paper contributes to the topic presenting results of experiments investigatingthe flow field around a cube and a hemisphere mounted on a bed surface with wake interferenceroughness. The velocity field and the drag force exerted on the obstacles were measured witha 3D Laser Doppler Anemometer and a drag force sensor, respectively. The double averagingmethodology (DAM) was applied to define the characteristic region influenced by the cube andthe hemisphere, and to analyse the streamwise velocities. DAM was developed for canopy flow,thus, the methodology needed to be adapted for isolated obstacle situations. A dependency ofthe drag coefficient on the relative submergence is observed and analysed.

Keywords: Flow resistances, Shear stress partitioning, Surface and form drag, DANS


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Experimental measurements of flood-induced impact forces onexposed elements

Michael Sturm1 ∗† , Bernhard Gems1 , Florian Keller1 , Bruno Mazzorana2 , SvenFuchs3 , Maria Papathoma-Kohle3 , Markus Aufleger1

1 Unit Hydraulic Eng., University of Innsbruck – Technikerstraße 13, 6020 Innsbruck – Austria2 Inst. Earth Sciences, Univ. Austral de Chile, Valdivia – Chile

3 Inst. Mountain Risk Eng., Univ. Natural Resources & Life Sciences, Vienna – Austria

The damage potential of buildings exposed to fluvial hazards is significantly high in mountain regions.

Settlements located on flat alluvial fans of torrents with steep upper catchment parts are particularly

exposed by these threats. A substantial availability of sediment in the catchments, being partly mobilized

during heavy rainfall and relocated to the alluvial fan, may cause an overloading of the channel capacities

and, consequently, an insufficient onward movement of the water-sediment-mixture. This leads to channel

outbursts of the torrent and buildings located on the alluvial fan get impacted and potentially damaged

by the hazard processes. Among other mechanisms, the impact forces on buildings resulting from tor-

rential hazards are crucial for the damage extent and for targeted risk reduction measures. However,

quantifying the hazard intensities as well as their spatial and temporal patterns may be challenging due

to the complex flow processes and their interaction with the building structures.

In this paper, impact forces of fluvial hazards on buildings exposed were investigated by use of a physical

scale model. Therefore, the Schnannerbach torrent channel (Austria) and its alluvial fan was used as a

case study and scaled 1:30 by Froude similarity. Three buildings were set up on the modelled alluvial fan

in the laboratory and equipped with measurement devices on 16 wall elements in order to detect triaxial

impact forces with high accuracy and a resolution of 200 Hz. Beside the impact forces, flow velocities

and incidental flow heights, such as deposition heights at the element wall, were measured within the

alluvial fan. The measured values of these parameters were correlated with the impact forces and used

for numerical model calibration. Specific fluviatile hazard scenarios under clear-water conditions and

with continuous bed-load supply were simulated. Therefore, discharge and grain size distribution were

varied and their influence on the process pattern and on the impact forces were measured. The effects

of surrounding buildings on the alluvial fan were further tested by setting up additional buildings in the

model environment. The locations of the wall elements and their exposition to the hazard processes were

analyzed. Potential influences of openings in the buildings envelope such as doors and windows were also

considered.

The experiments show that the impact forces are relatively independent from the hazard scenario itself,

with respect to the discharges and grain size distributions, especially for sediment-laden flow conditions.

Observed impact forces mainly depend on the developed flow paths on the alluvial fan, influenced by

surrounding buildings and the sediment deposition pattern on the floodplain. For the introduced correla-

tions of incidental flow heights and impact forces, both for clear-water and sediment-laden flow conditions,

calculation approaches are well applicable for estimations of impact forces in practical use, since they

only contain explicit and quantifiable process parameters. The scale model experiments were numerically

reconstructed with the software BASEMENT, a 2D-numerical model. The common applicability and po-

tential limits of simultaneously calculating complex flow and deposition processes in a steep and narrow

torrent channel and on a flat floodplain were analyzed. The modelling experiences and the determined

calibration parameters can be applied to different floodplains, where physical scale model experiments

are not available. Finally, concerning the damage potential of the buildings due to fluviatile processes,

the experiments show that impact forces do not necessarily lead to sustainability failure of the entire

structure without the support of further mechanisms such as abrasion, scouring effects and undermining


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of the buildings.

The presented work delivers highly valuable and physics-based information on the impacts of fluviatile

hazard processes in mountain streams and torrents and the fluid-building-interaction on alluvial fans.

The findings are applicable in practical use, e.g. for land use planning, hazard zone mapping and vulner-

ability analyses of buildings susceptible to torrential hazards, respectively.

The study is part of the project ”Vulnerability analysis of buildings exposed to torrent hazards – small-

scale experimental modelling of impacts on buildings and derivation of physics-based vulnerability func-

tions”, funded by the Austrian Science Fund (FWF; P27400-NBL).

Keywords: Bed Load Transport, Impact Force, Flood, Physical Scale Model, Vulnerability

92


Turbulent kinetic energy in a water worked stream

Ellora Padhi ∗† 1, Subhasish Dey 1, Nadia Penna 2, Roberto Gaudio 2, Venkappayya RDesai 1

1 Indian Institute of Technology – Kharagpur 721302 – India2 Univ. della Calabria, Laboratorio di documentazione – Via Pietro Bucci, 87036, Rende – Italy

Turbulent stream over a gravel bed is one of the important topics of discussion due to its intricate

behaviour in the near-bed flow zone. Near the bed, the flow is highly influenced by the fluid-gravel

interactions and becomes nonhomogeneous. In the laboratory, to replicate the flow characteristics of

a natural gravel bed stream, it is pertinent to reproduce the bed topographic condition of a natural

stream to ensure a faithful representation of a natural bed. It is however common to create the bed in a

laboratory flume by placing the gravels randomly in the flume and then screeded manually. Such a bed is

quite different from the bed observed in a naturally. To improve this issue, the screeded gravel bed (SGB)

is required to be water worked before performing the experiments to achieve a bed surface topography

resembling to that of a natural stream bed. Such a bed is termed water-worked gravel bed (WGB).

The bed surface topography of WGB was studied by some researchers (Cooper and Tait 2008; Hardy et

al. 2009). However, its effects on the near-bed flow characteristics, especially the turbulent kinetic energy

(TKE) fluxes and budget which play dominant role in the overall structure of the near-bed flow are yet

to be explored thoroughly. Further, to resolve the near-bed flow heterogeneity, the double averaged (DA)

turbulence characteristics (TKE components, TKE fluxes, TKE budgets and so on) are analysed for the

both WGB and SGB. The results of both the beds are compared to understand the effects of the change

in bed surface topography on turbulence characteristics.

Experiments were conducted for both the WGB and SGB, by using the particle image velocimetry (PIV).

Coarse gravels having a unimodal distribution (4 < d < 6 mm) with a median diameter of 4.81 mm

was used as a bed material. To keep the bed slope same as flume bottom, the gravel bed was screeded

manually, thus the SGB was formed. The slope of the SGB was measured and found to be 0.7%. Later,

the SGB was water-worked by using a flow Froude number of 0.88. During the WGB preparation, the

sediment transport took place over a period of 28.5 h, when its rate declined from 0.072 to 0.0003 kg

m–1 s–1, since there was no gravel feeding. At the end of this phase, the bed slope was measured and

found as 0.4%. For both the WGB and SGB, all the measurements were taken in the test section, where

the flow was quasi-uniform, since during the experiments the flow depth of 0.10 m was controlled by an

adjustable tailgate, with a constant Froude number of 0.52.

A significant change in bed surface topography was observed due to the process of the water work,

resulting in different roughness geometries for the WGB and SGB. The roughness height of the SGB

was found to be higher than that of the WGB. The DA streamwise and vertical TKE components for

both the WGB and SGB were analysed. In the near-bed flow, the TKE components of the WGB attain

higher values than those of the SGB. The reason is attributed to a larger surface roughness of the SGB.

Then, the form-induced streamwise and vertical TKE components for both the WGB and SGB were

investigated. The streamwise form-induced TKE component for the SGB attains a higher value than

that for the WGB. The possible reason is due to the change in spatial orientation of the gravels for the

SGB. Thereafter, the DA streamwise and vertical TKE fluxes for both the beds were examined. The DA

streamwise and vertical TKE fluxes for both the beds change their sign above the gravel crest, signifying

a changeover of the bursting events. The DA TKE fluxes for the WGB attain a higher value than that

for the SGB due to the change in surface roughness. The form-induced streamwise and vertical TKE

fluxes attain higher values for the WGB than those for the SGB due to the higher roughness height for

the SGB. Finally, the DA TKE budget was analysed for both the WGB and SGB. Near the bed, all the

components (production, diffusion, dissipation and pressure energy diffusion rate) of TKE budget for the


93



WGB are larger than those for the SGB due to the higher roughness height and the different orientation

of the roughness elements for the SGB.

Keywords: water worked gravel bed, TKE budget, double averaging method

94


Dam break over mobile bed: characterisation of the flow bymeans of pressure distribution and bed shear stress.

Ilaria Fent 1, Mario Franca ∗ 2, Sandra Soares-Frazao † 1

1 Universite catholique de Louvain (UCLouvain) – Belgium2 IHE Delft Institute for Water Education – Netherlands

The study of the pressure distribution within the dam-break flow over mobile bed is veryimportant because it allows to discuss the hydrostatic pressure distribution, which is the mainassumption for the validity of the shallow water equations (SWE). Indeed, this assumption isnot always valid, especially when the streamlines are not straight and not perpendicular tothe gravity acceleration direction. The flow varies abruptly in the first instants of the fallingdam-break wave evolution, but it tires towards a stationary motion during time. To bettercharacterize this phenomenon it is important to examine the evolution of each component ofvelocity vector field and the distribution of the pressure, which is compared to the hydrostaticdistribution. Moreover, the present study considers the distribution of pressure linked withthe distribution of the shear stress, through the Navier-Stokes equations. The final object ofthis work is to characterize the dam break experiment over mobile bed by means of forcesacting during the event. The dam-break experiment under examination has been performedin a dedicated flume designed at the laboratory of Civil Engineering Department, Universitecatholique de Louvain. The analysis of this very transient flow it is now possible and moreaccurate thanks to the application of non-intrusive new techniques, such as PIV.

Keywords: dam break, experiments, severe transient flow, velocity field, pressure distribution, shear

stress


95



Experiments on turbulence and near bank vorticities in an openchannel sharp bend

Alireza Farhadi ∗† 1, Christine Sindelar 2, Michael Tritthart 2, Helmut Habersack 2

1 University of Natural Resources and Life Sciences, Vienna – IWHW, Universitat fur BodenkulturMuthgasse 18, A-1190 Wien, Austria

2 University of Natural Resources and Life Sciences, Vienna – Austria

Turbulence has a significant influence on fluvial processes. Especially in the sharp bends ofgeometrically complex natural streams, the interaction of turbulence and flow three-dimensionalitiesis considerable. Here, generation and evolution of streamwise vorticity in an open channel bendis assessed by means of term-by-term experimental investigations. As a result, correspondingmechanisms are shown and analysed. In addition, based on the homogeneity term of vorticityequation, the applicability of a widely used simplified equation of streamwise vorticity is dis-cussed. The presented comparison reaffirms the inadequacy of the equation in order to estimatenear bank vorticities.

Keywords: sharp bend, vorticity, experimental, homogeneity


96



Experimental study of the transient motion of floatsreproducing floating wood in rivers

Hossein Ghaffarian ∗† 1, Diego Lopez 1, Nicolas Riviere 1, Emmanuel Mignot 1, HervePiegay 2

1 INSA Lyon – LMFA, Univ. Lyon, INSA de Lyon – France2 ENS de Lyon – CNRS UMR 5600 EVS, Univ. Lyon – France

The presence of large wood in rivers can damage hydraulic structures, especially in urban areas. Thus,

understanding more about the dynamics of such floating objects is crucial for reducing the associated risk

and maintenance costs. Many studies focused on statistics of wood flux and jam formation on obstacles, in

particular considering the effect of obstacle shape (such as bridge piers), flow characteristics (shallowness,

velocity) and wood geometry. Additionally, there have been several studies on the drag force due to flow

on logs and cylinders, providing information on the effect of geometry on the drag. However, only few

studies looked at the effect of this force on the transient motion of wood, essentially focusing on the

starting motion of logs lying on the floodplain, and there is still a lack of understanding of the transient

dynamics of isolated or grouped floating pieces of wood.

In this work, we study theoretically and experimentally the transient dynamics of floating particles

considering the simple case of acceleration under a uniform and unidirectional flow; this problem can

be modeled by a standard advection equation for large Reynolds number particles. Using the non-

dimensional formulation of this model, we identify a key parameter that drives the particle response

to the flow. This parameter is a ratio between a characteristic streamwise distance and a typical flow

length scale. This characteristic distance, which depends on the particle properties, provides an order of

magnitude of the distance travelled by the particle during its acceleration phase. Therefore, we refer to

it as the particle characteristic response distance. In the case of a flow around an obstacle, two situations

can be faced: when the ratio between this distance and the flow length scale is small, the particle follows

the flow streamlines. Conversely for larger values of this ratio, the particle trajectory diverges from the

streamlines, and thus the floating object will be more likely to hit an obstacle or a river bank.

The characteristic response distance of different particles was measured in a 1D experiment of particle

acceleration under a uniform flow. Three groups of floating particles were used: disks, logs without root

and logs with idealized roots. First, the methodology was established using disks as the simplest isotropic

geometry. Their aspect ratio, defined as the ratio between their length and diameter, ranges from 0.1 to

0.8. Then, to adopt a more realistic geometry for floating wood, we tested cylindrical logs aligned in the

streamwise direction with aspect ratios from 1 to 20. Finally the effect of a root-wad was investigated

using idealized roots with different lengths (from 3 to 7 times the trunk diameter) and different number

of roots (2 to 8). Our experiments were carried out in a straight, rectangular (8m long and 0.25m wide)

glass-walled flume where the surface flow velocity was measured by particle tracking velocimetry (using

small tracer particles).

We first find that the 1D model matches perfectly with the experimental data, and that for all particles

the characteristic response distance is typically about 2 times the body length in the streamwise direction.

The evolution of this distance with the particle aspect ratio shows that the longest response distance for

logs is reached at an aspect ratio of 5. The comparison of this critical value with field data on the

typical shape of floating wood could provides useful indications for risk management. Additionally, the

comparison of different root patterns showed that the particle response distance is independent of the

precise root-wad shape but is only a function of the resulting frontal area. Consequently, our results can

be easily extended to actual pieces of wood with complex geometries.

Keywords: Large wood, Wood dynamics, Transient motion, Drag force


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Studies on driftwood motions around obstacles by laboratoryand numerical experiments

Ichiro Kimura ∗† 1, Kazuya Kitazono 2

1 University of Toyama – 3190 Gofuku Toyama 930-8555 – Japan2 Chubu Electric Power Co. Inc. – Japan

It is important to predict driftwood motions around hydraulic structures such as bridgepiers, spur-dikes, fish ladder, etc., from the viewpoints of disaster prevention because collisionof driftwood can damage river structures and also deposited driftwood may increase flow resis-tance. We proposed a numerical model to simulate driftwood motions based on the coupling ofa Eulerian type three-dimensional flow model and a Lagrange type two-dimensional driftwooddynamics model.In order to validate the performance of the present numerical model, laboratory experiments ondriftwood motions in a curved open channel with obstacles were carried out for obtaining thereference data. The experiments were performed with a meandering experimental flume madeof plexiglass with 20cm in the width and 3m in the length. The laboratory experiments wereconducted by changing flow conditions for 10 cases.The computational results showed that the three-dimensional flow features considerably affectthe behavior of driftwood in a curved part because the secondary current of the first kind causedby the unbalance of the centrifugal force is induced strongly. We compared the computationalresults by the 3D (three-dimensional) and 2D (two-dimensional) flow models and found that the3D model is necessary to predict well the motion of driftwood at curved channel.We defined a non-dimensional driftwood settling parameter to consider the three-dimensionalbehavior of driftwood settlement around obstacles. The experimental results showed that ifthe driftwood settling parameter is small, the capturing of driftwood by the obstacles happenstwo-dimensionally confined near the water surface. On the other hand, if the driftwood settlingnumber increases, the deposition of driftwood around obstacles occur more three-dimensionally,that means some driftwood goes underneath the previously settled driftwood, and then formsa vertical stack of driftwood at upstream regions of the obstacles. We also found that if thedriftwood settling number increases, the rate captured driftwood increases.

Keywords: driftwood, river structures, numerical model, open channel flows


98



Calibration of a numerical model for the transport of floatingwooden debris

Elisabetta Persi1 ∗† , Gabriella Petaccia1 , Stefano Sibilla1 , Jose-Ignacio Garcıa-Palacın2

, Pilar Brufau2 , Pilar Garcıa-Navarro2

1 University of Pavia – Italy2 University of Zaragoza – Spain

The paper describes the calibration of a numerical model which simulates the two-dimensionalmotion of rigid floating debris, in particular of wooden logs which can flow on the water surface,during a flood. This topic is of increasing interest, since large floating debris can enhance andworsen the consequences of floods. When wooden elements come across inline structures, theycan stop against bridge piers, triggering the accumulation of other debris until partial or com-plete blockage of the bridge openings. The resulting backwater effect can provoke the floodingand the damage of larger areas as well as endangering a higher number of people in urban zones.The proposed model follows a one-way coupling Eulerian-Lagrangian approach, where the so-lution of the Shallow Water Equations is combined with the Discrete Element Method for thecomputation of the displacement of rigid bodies. The translation of logs is computed by adapt-ing the Maxey-Riley equation to the case of semi-submerged bodies at high Reynolds number.In order to account for the velocity distribution on the bodies length, a division of the elementin shorter subsections is provided. In this way, the distribution of the load exerted by the flowalong the body axis can be satisfactorily approximated. A specific formulation is proposed forthe rotation of wooden cylinders, taking advantage of the distribution of the hydrodynamicforces on the body for the angular momentum equilibrium computation. The model includesalso a term of added inertia, which accounts for the resistance to rotations and requires thecalibration of a specific inertia coefficient.With the aim to verify the proposed formulation, a series of experiments was performed in alaboratory channel at the University of Zaragoza. The 2D trajectories of floating spheres andcylinders were recorded in the case of stationary uniform and non-uniform flow. The latter con-figuration was obtained by positioning side obstacles of different shapes –smooth and abrupt– inorder to assess the behavior of floating bodies in both conditions. The experimental trajectoriesare compared with the ones simulated by the proposed SWE-DEM model (black line versus lightblue line in Figure 1).The results of spheres motion, which did not rotate significantly in the experiments, show thatthe translation model is accurate enough and allows the validation of the subdivision of thebody in smaller segments. When the semi-submerged bodies are cylinders, it is not possibleto separate the translation and rotation formulations because the body orientation affects bothcoefficients and the direction of the hydrodynamic forces. Drag and side force coefficients forsemi-submerged cylinders were preliminarily obtained from laboratory experiments and theirvariation with the cylinder orientation is properly modelled. The added inertia coefficient is in-stead set to a constant value, calibrated through a sensitivity analysis on a series of experimentswith different configurations. The experimental and simulated trajectories are in agreement, aswell as the angular displacement, which registers, however, a smaller accuracy.

Keywords: Wood transport, laboratory experiments, model calibration


99



Hazards due to large wood accumulations: Local scour andbackwater rise

Isabella Schalko ∗† 1, Lukas Schmocker 1, Volker Weitbrecht 1, Robert M. Boes 1

1 Laboratory of Hydraulics, Hydrology and Glaciology; Swiss Federal Institute of Technology Zurich(VAW, ETH Zurich) – Switzerland

Large wood (LW) in rivers is defined as logs with a diameter ≥ 0.1 m and a length ≥ 1.0 m.It plays a relevant role for the river ecosystem, as it increases the flow diversity and provideshabitats for species. During flood events, transported logs can accumulate at river infrastruc-tures and increase the flood hazard. LW accumulations result in an upstream backwater riseand may increase local scour, for instance at bridge piers. In addition, backwater rise due tothe intentional LW accumulation at retention racks may disrupt the sediment continuity. Con-sequently, estimates of the resulting backwater rise and local scour are necessary to improvethe flood hazard assessment. This study presents the findings on local scour and backwater risedue to LW accumulations with a moveable river bed. Flume experiments were conducted at theLaboratory of Hydraulics, Hydrology and Glaciology (VAW) at ETH Zurich in the course ofthe interdisciplinary research project WoodFlow – Management of LW in Swiss rivers. Duringthe experiments, the approach flow conditions (inflow Froude number and flow depth) and bedmaterial (uniform material and sediment mixture) were varied systematically for a specific LWaccumulation volume. For all experiments, the initial condition for the bed material was definedas weak transport, since the bed shear stress was slightly below the critical bed shear stress forincipient motion. The Froude number was identified as the governing parameter for backwaterrise due to LW accumulations. The present study confirms the hypothesis that the resultinglocal scour reduces backwater rise. For the local scour, the specific discharge and the grain sizeare the decisive parameters. Higher specific discharge and finer material lead to an increasedscour depth. As a next step, the findings of this study will be combined in a design equation toestimate backwater rise and local scour. Hence, the hazard assessment of river infrastructuresand the design of LW retention structures can be significantly improved for flood events withhigh LW transport.

Keywords: Backwater rise, Flood protection, Flood risk assessment, Large wood (LW), River

engineering, Scour


100



Spillway blockage caused by large wood in reservoirs

Paloma Furlan ∗† 1,2, Michael Pfister 3, Jorge Matos 2, Anton J. Schleiss 1

1 Laboratory of Hydraulic Constructions, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne– Switzerland

2 Instituto Superior Tecnico, Universidade de Lisboa, Lisboa, Portugal (IST) – Portugal3 Haute ecole d’ingenierie et d’architecture Fribourg (HEIA), HES-SO – Switzerland

Large wood (LW) elements are often transported by rivers into reservoirs during heavy rain-fall events. Large wood has important environmental attributes that benefit the diversificationof riverine ecosystems. There are several studies dealing with the transport and behaviour of LWinside streams. However, during flood events, LW tends to create jams or blockages at diversehydraulic structures inside streams, creating significant problems such as discharge limitationsand increased water levels. Even though knowledge on the effect of LW at bridges in rivers withrelatively high flow velocities starts to be available, the latter is hardly applicable for reservoirapproach flow conditions. Understanding LW blockage processes at a reservoir spillway is essen-tial regarding the safety evaluation of a dam and the surrounding areas. The geomorphologicbenefits of wood for stream restoration depends also on our present ability to manage jams andthe risk they imply for civil structures when blocked. Therefore, series of systematic laboratoryexperiments were conducted to analyse blockage of floating stems at an ogee crested spillwayequipped with piers. Different LW characteristics were represented in a physical model withcylindrical stems. Results associate the size of stem groups to blockage probabilities and theeffect blockages can have on the discharge capacity of a spillway.

Keywords: Large wood, blocking probability, ogee crest, spillways, floods


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Thursday 6 September, 10:55 – 12:35 Li 4 – Bedform and sediment transport

Quantification of bed-load transport over dunes

Kenneth Lockwood 1, Patrick Grover 1, Ana Maria Ferreira Da Silva ∗† 1

1 Department of Civil Engineering, Queen’s University – 58 University Av. Kingston, ON K7L 3N6,Canada

Dunes are the most common type of bed forms occurring in sand rivers, and have a signifi-cant impact on both hydraulic roughness and sediment transport. Owing to their practical andscientific significance, extensive research has been dedicated to dunes for many years. In spiteof this, many aspects of dune dynamics, and in particular the coupling of flow and sedimenttransport remains unclear. In this context, there appears to be disagreement on how to quantifylocal sediment transport rates over dunes. The matter acquires particular importance whencalculating the downstream migration of dunes, or the morphological changes they experienceunder changing flow conditions. This paper concerns the quantification of local sediment rates.The work is restricted to the case of bed-load.As is well-known, existing equations for the quantification of bed-load rate (Meyer-Peter, Bag-nold, etc.) were developed for uniform flow conditions. Such equations almost invariably givebed-load rate as a function of the bed shear stress. However, the flow over dunes is not onlynon-uniform, but also internally highly complex. The flow suddenly expands downstream of thedune crest, it separates from the boundary, and reattaches to it at approximately 4 to 6 timesthe dune height. As the flow progresses downstream, an internal boundary layer develops withthe flow accelerating over the stoss side of the dune. The question that arises is whether existingequations can represent bed-load rate in the accelerating region downstream of the reattach-ment point. For this to happen, the bed-load rate must be directly related to the local bedshear stress as the flow accelerates. On the basis of experimental results, it has been suggestedby a number of authors that such an approach may not be appropriate. On the other hand,in direct contradiction to such conclusions, several recent numerical dune morphological modelsemploying existing equations have produced results that compare favorably with experimentaland field data. Considering the aforementioned, the specific objective of the present work is toexperimentally investigate the applicability of existing bed-load rate equations to the flow overdunes outside of the recirculation zone.For the present purposes, an experiment was carried out in a 21 m long, 0.76 m wide sedimenttransport flume of Queen’s University. In this experiment, a sequence of fully developed dunesre-creating those produced in a previous study were constructed, and then immobilized so as toenable the measurement of the flow field and turbulence characteristics over them. Flow velocitymeasurements were carried out using a Nortek Vectrino II Acoustic Doppler Velocimeter. Thesemeasurements were then used in combination with results from an advanced numerical model tocalculate bed shear stress, bed-load rates, and subsequently the related morphological changes.The predicted and observed changes to bed morphology were compared and found to be in goodagreement. This suggests that current bed-load rate equations can accurately predict sedimenttransport over dunes outside of the recirculation zone.

Keywords: Rivers, Dunes, Morphological Changes, Sediment Transport


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A flume study to investigate the contribution of main-channelbedforms on levee formation

Till Branß ∗† 1, Francisco Nunez-Gonzalez 1, Andreas Dittrich 1, Jochen Aberle 1

1 Leichtweiß-Insitut fur Wasserbau, TU Braunschweig (LWI) – Beethovenstr. 51a, 38106 Braunschweig– Germany

Natural levees are narrow elevated sediment deposits along the floodplain edge of compoundchannels. They are formed during overbank flows, when sediment from the channel bed is setin suspension and transferred onto the floodplain, and act as natural embankments, influencingflow patterns and the morphological development of the floodplain.Natural levees have been described in many field studies (e.g. Pizzuto, 1987; Ferguson & Brierley,1999; Filgueira-Rivera et al., 2007) and different processes have been suggested to explain theirformation and highly varying geometry. For example Adams et al. (2004) related the diverselevee geometries to different mechanisms of lateral sediment transfer. They suggested that leveesgenerated by turbulent shear between the main channel and floodplain exhibit a narrow andsteep geometry while levees resulting from advective transport, caused by differences in the watersurface elevation between main channel and floodplain, tend to be wider and less steep. Otherstudies (e.g. Cazanacli & Smith, 1998) revealed a strong relation between overbank sedimenttransfer and the water depth ratio between the main channel and the floodplain. This indicatesa detailed understanding of the relevant variables and processes for the formation of naturallevees, is still far from complete. Especially the influence of riparian vegetation as well as mainchannel bedform configurations have not yet been investigated in depth.This paper focuses on the relations between the characteristics of the bed configuration in themain channel, and the amount of sediment deposited on the floodplain edge. For this purpose,experiments were performed in a 2 m wide and 30 m long sediment recirculating flume usinga cross-section of a half trapezoidal compound channel. Light-weight material was used assurrogate sediment to accelerate morphodynamic development within the experimental runs andto initiate overbank sediment transfer. Bed level changes in the main channel were continuouslyrecorded by ultrasonic sensors in two transversal sections, while the lateral growth of the leveedeposits was extracted from plan view photos, taken automatically on a regular basis duringthe entire experiments. Results are presented for different bed configurations, obtained bycontrolling the amount of recirculated light-weight material. A preliminary comparison betweenthe bedform configurations and the associated levee-like deposits shows a positive correlationbetween the amount of levee sediments and the mean bedform height. Furthermore, bedformspertaining to the upper 20% of the density distribution of bedform heights, strongly enhanced thegrowth of the levee by promoting the transfer of large quantities of sediment onto the floodplain.The analysis additionally indicates that the bedform geometry has a high impact on the amountof sediment transferred onto the floodplain. In light of the experimental results, the effect ofbedforms on levee formation processes will be discussed.

Keywords: natural levee, bedforms, compound channel


103



Influence of hydrology, sediment supply and sediment sortingon bar morphodynamics (Loire River, France)

Florian Cordier ∗ 1, Pablo Tassi 1,2, Nicolas Claude † 1, Alessandra Crosato 3,4, StephaneRodrigues 5,6, Damien Pham Van Bang 2

1 Laboratoire National d’Hydraulique et d’Environnement (LNHE) EDF R&D – 6 quai Watier, 78401Chatou Cedex – France

2 Laboratoire d’Hydraulique Saint-Venant – Ecole des Ponts ParisTech, EDF R&D, CEREMA – 6 quaiWatier, BP49, 78401 Chatou Cedex – France

3 IHE Delft Institute for Water Education (IHE Delft) – Westvest 7, Delft – The Netherlands4 Delft University of Technology (TU Delft) – Building 23, Stevinweg 1, 2628 CN, Delft – The

Netherlands5 Ecole Polytechnique Universitaire, Universite de Tours (Polytech Tours) – 35 allee Ferdinand de

Lesseps, 37200 Tours, France6 UMR CNRS CITERES 7324 (CItes, TERritoires, Environnement, Societes) – CNRS : UMR7324 – 35

Allee Ferdinand de Lesseps - 37000 Tours, France

Rivers inherently show heterogeneous sediment sizes and can also show a strong sedimentsupply variability in time because of natural episodic events or as a consequence of human activi-ties, which alter the characteristics and dynamics of alluvial bars at the macro-scale. The impactof the combination between sediment size heterogeneity and sediment supply variation, or evenwith other forcings (i.e. hydrology, channel geometry) remains poorly documented. In this work,a physics-based numerical model is applied on a trained reach of a sandy-gravel bed river toinvestigate the combination of these parameters on bar morphodynamics. The morphodynamiccomputations are performed with a two-dimensional depth-averaged hydrodynamic solver, inter-nally coupled to a sediment transport and bed evolution module, which estimate the transportof graded sediment and model bed stratigraphy, respectively. A 1 km long reach of the LoireRiver at Brehemont (France) is selected to conduct the numerical investigations. The interac-tion between several forcing mechanisms induces highly complex bar morphodynamic processesin this area.A comprehensive set of high-definition data is available, which allows to study theriver morphodynamics for a succession of three flooding events and a period of low flows. Basedon this model, a variety of scenarios is presented with the aim of exploring the implications ofsediment gradation, geometrical and boundary forcing eects on in situ bars morphodynamics.

Keywords: alluvial bars, sediment size heterogeneity, sediment supply, numerical modelling, mor-

phodynamics


104



Geomorphic effects of gravel augmentation on the Old RhineRiver downstream from the Kembs dam (France, Germany)

Valentin Chardon ∗ 1,2, Laurent Schmitt† 2, Herve Piegay 1, Fanny Arnaud 1, JordaneSerouilou 2, Jerome Houssier 2, Anne Clutier 3

1 Environnement Ville Societe (EVS) – CNRS UMR 5600, Univ. Lyon – 18 Rue Chevreul 69362 LyonCedex 07 – France

2 Laboratoire Image Ville Environnement (LIVE) – CNRS UMR 7362 LIVE, Univ. Strasbourg– 3 Ruede l’Argonne 67083 Strasbourg cedex – France

3 Centre d’Ingenierie Hydraulique (CIH-EDF) 15 avenue Lac du Bourget Passerelles Savoie Technolac73373 Bourget-du-Lac – France

The Old Rhine is a 50 km by-passed reach downstream from the Kembs diversion dam inthe Alsacian plain (France/Germany). It has been impacted by engineering works since the19th century. This reach exhibits poor ecological functionalities due to severe geomorphologi-cal alterations (e.g., channel bed stabilization, narrowing, degradation and armoring, sedimentdeficit). In the frame of the Kembs power plant relicensing (2010), Electricite de France hasundertaken two gravel augmentations (18 000 and 32 000 m3) to promote bedload transport. Afirst pilot gravel augmentation was also implemented in 2010 (23 000 m3). A geomorphologicalmonitoring based on bedload tracking, grain size analyses and topo-bathymetric surveys hasbeen performed on the three gravel augmentation reaches to assess the efficiency and sustain-ability of these actions (2010-2017).Results show that augmented gravels are entrained for a Q2 flood. Gravels moved several hun-dred meters for moderate floods and up to one kilometer for intense floods (Q15), while sedimentdeposition mainly diffused within the channel. The mobilization of augmented gravels dependsto the deposit placement and configuration. Bed armoring reestablished once the sediment wavemoved further downstream, after only four to six years, due to the stability and the narrownessof the channel and the absence of upstream bedload supply. The virtual velocity decreased overtime due to progressive tracer burial in the subsurface layer and trapping in the armor layer.Morphological and grain size diversification, including sediment refinement, were relatively lim-ited spatially. Furthermore, the risk of rapid sediment transfer towards channel navigation wasdiscarded.Monitoring results demonstrate that gravel augmentations are not sufficient to diversify geo-morphological conditions of the Old Rhine. Channel enlargements by controlled bank erosionand other actions should be carried out downstream from gravel augmentations to create chan-nel geometry conditions promoting bar development and habitat diversification. A attentionshould be carried on the grain size of future augmented gravels in order to limit bed armoringdevelopment.

Keywords: river restoration, large rivers, gravel augmentation, geomorphic monitoring, sediment

tracking, grain size analysis, LiDAR Topo, bathymetry


105



Hydrodynamic Simulation of an Irregularly MeanderingGravel-Bed River: Comparison of MIKE 21 FM and Delft3D

Flow models

Parna Parsapour-Moghaddam ∗† 1, Colin Rennie 1, Jonathan Slaney 2

1 University of Ottawa – Canada2 The City of Calgary – Canada

This study aims at hydrodynamic modelling of Bow River, which passes through the Cityof Calgary, Canada. Bow River has a mobile gravel bed. Erosion and deposition processes wereexacerbated by a catastrophic flood in 2013. Channel banks were eroded at various locations,and large gravel bars formed, which could lead to water level changes and accordingly moreflooding. This study investigates the performance of Delft3D-Flow and MIKE 21 FM to simulatethe hydrodynamics of the river during the 2013 flood. MIKE 21FM employs unstructuredtriangular mesh while Delft3D-Flow model uses curvilinear structured grids. Performance ofeach model was evaluated by the available historical water levels. The results of this studydemonstrated that, with approximately the same averaged grid resolution, MIKE 21 FM resultedin more accurate results with a higher computational cost compared to the Delft3D-Flow model.It was shown that Delft3D-Flow model may require higher grid cell resolution to result incomparably same depth-averaged velocities throughout the study area. However, consideringthe balance between the computational cost and the accuracy of the results, both models werecapable to adequately replicate the hydrodynamics of the river during the 2013 flood. Resultsof statistical KS and ANOVA test analysis showed that the model predictions were sensitiveto the horizontal eddy viscosity and the Manning roughness. This confirms the necessity of anappropriate calibration of the generated numerical models. The findings of this study shed lighton the Bow River flood modelling, which can guide flood management.

Keywords: Hydrodynamic modelling, Gravel bed, Meandering River, Delft3D Flow, MIKE21 FM,

Bow River


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Thursday 6 September, 10:55 – 12:35 Br 4 – Management of hydrological extremes

The German National Flood Protection Programme: evaluatingthe impact of supra-regional flood protection measures on

extreme floods using hydrodynamic modelling

Carina Schuh ∗† 1, Marcus Hatz 1

1 Federal Institute of Hydrology (BfG) – Am Mainzer Tor 1 56068 Koblenz, Germany

After the disastrous flood events of June 2013 in the German Elbe and Danube catchments,the German government together with the federal states decided on the joint elaboration ofa nationwide flood protection programme (NHWSP, 2015-2027+). Within the frame of thisprogramme, the government supports the realization of large-scale retention measures for theimprovement of supra-regional flood prevention. For scientific monitoring, the Federal Instituteof Hydrology (BfG) was mandated to conduct a two-part preparatory ad hoc study (2014-2015)and a subsequent research project (2015-2019) evaluating the collective impact of the plannedretention measures on flooding processes and flood peak reduction in the Danube, Elbe, andRhine basins. Findings from the ad hoc study provided the government with first elements ofevidence for taking its decision on the elaboration of the NHWSP programme, and supported thedevelopment of a modelling strategy for the accompanying research project. By using extensivesets of hydrodynamic models, the research project takes into account the complex interrelationsbetween supra-regional flood formation, flooding process, and retention control concepts whenevaluating flood reduction on catchment level. It is expected to technically substantiate thegovernment’s NHWSP programme by refining the criteria for identification and prioritization ofmeasures.

Keywords: flood protection, retention, hydrodynamic modelling, SOBEK River, supraregional,

Danube, Elbe, Rhine


107



Hydraulic function of the Kasumi levee system on the Kurobealluvial fan of the 19th century

Hiroshi Senoo ∗ 1, Tadaharu Ishikawa † 2

1 TOKEN C.E.E. Consultants Co., Ltd. – 1-15-6 Kitaotsuka, Toshima-ku, Tokyo 170-0004 – Japan2 Tokyo Institute of Technology – 2-4-15 Katasekaigan, Fujisawa-shi, Kanagawa 251-0035 – Japan

A system of discontinuous levees, commonly called kasumi (meaning haze) levees, was builtin Japan in the 18th and 19th centuries and maintained until the early 20th century. The systemcontained a variety of levee arrangements depending on local topography, land use and socialconditions, and their design concept and hydraulic effects have not been fully understood. Inthis study, the hydraulic function of the kasumi levee system constructed along the KurobeRiver was investigated using numerical flow simulations. The Kurobe River has its source in thecentral mountains of Japan’s main island, and the main channel undergoes an elevation changeof 3,000 m over 85 km before entering the Japan Sea. The large volume of sediment carried bythe river forms an alluvial fan with a radius of 13 km, a top angle of 60◦ and an average slope of1/100 at the downstream river reach. The kasumi levee system on the alluvial fan was completedin the early 19th century to unify several diverging channels into one stable channel. A shallowwater model including an expression of levee overtopping with an unstructured triangular meshsystem 1), 2) was adopted for the numerical flow simulations. Due to the absence of data for theKurobe River in the 19th century, the computation conditions were determined based on manydifferent types of record from the period. The channel capacity was estimated as 2,700 m3/sbased on the average flood frequency recorded at the time, along with hydrological statisticsobtained over recent 80 years. Three flood hydrographs were assumed for the simulations bychanging the scale of the hydrograph recorded in 1969 with a peak discharge greater than 3,000m3/s. GIS data (2016) was used for the ground elevation distribution on the alluvial fan byeliminating the recent highways and railways. The locations of kasumi levees were determinedbased on the 1894 records of Johannis de Rijke, a technical advisor from the Netherlands, andthe channel bed elevation was obtained from the longitudinal bed profile measured in 1969 beforemodern river improvement works. The results show that the overflow started from a west leveeopening near the top of the alluvial fan. The floodwater flowed through lowland regions alongthe west bank, and a portion of the floodwater returned to the main channel through a leveeopening in the middle reach. The inundation area and the returning flow were very similar tothose observed in the 1934 flood event when most of the kasumi levees still existed. In orderto investigate the flood protection works along the east bank against excess flooding due tochannel bed rises caused by sedimentation, an additional simulation was performed by assuminga channel bed rise of 1 m. The results show that the flood water from the upstream reach to theeast alluvial fan did not disperse widely and successfully returned to the downstream channelby longer doubled levees located in the middle reach. They also suggest that the kasumi leveesystem was well designed using the embankment technology of the day, based on a strategy ofpreventing inundation of the east part of the alluvial fan where villages and paddy fields werewell developed.

Keywords: the kasumi levee system, A shallow water model, an unstructured triangular mesh

system, flood risk management, alluvial fan


108



Balancing river restoration measures around a river bifurcation: a case study from the Netherlands.

Ralph Schielen ∗† 1,2, Bert Voortman 1, Tjeerd Driessen 3

1 Ministry Infrastructure & Water Management – The Netherlands2 Univ. of Twente – Dienstweg 1, Enschede – The Netherlands

3 RoyalHaskoning – The Netherlands

Shortly after the river Rhine enters the Netherlands, it bifurcates into three different branches by two

bifurcation points which lie only 10 km apart. The discharge partitioning over the bifurcates is extremely

important for the safety of the complete downstream area (more than 300 km of river stretch). That

is why this partitioning is highly regulated by two control structures in the adjacent floodplains near

the bifurcation points. These structures ensure that at high discharge conditions, the partitioning is in

accordance with the pre-set safety standards, and hence in accordance with the height and the strength

of the dikes in the downstream area.

The Netherlands are preparing themselves for the consequences of climate change. According to the

scenarios of the IPCC, discharge at extreme conditions is expected to increase. To mitigate this, the

Netherlands have adapted a Delta Program, in which combinations of flood level reducing measures and

dike reinforcements are studied. Measures in the vicinity of the bifurcation points, however, have a pos-

sible side effect in the sense that they could alter the discharge partitioning over the bifurcates if the

reduction of water levels is not equally balanced over the bifurcates. This effect increases flood risk in the

downstream areas and could change the flooding frequency of downstream flood plains. This effect can

be compensated by adjusting the settings of the control structures, but if the measure reduces the flood

level too much, the structures get out of range and cannot guarantee the correct discharge partitioning

anymore. This introduces an interesting dilemma, since the design of a river restoration measure aims for

a maximum reduction of flood levels. However, too much reduction on one bifurcate may affect the dis-

charge partitioning adversely and raises the need to execute expensive measures to increase the capacity

of the regulation works (if possible)., Another option is to to design a flood level reducing measure on the

other bifurcate or to reduce the original measure in size . In the latter case additional dike reinforcement

must be executed to guarantee the safety.

This paper describes how to obtain a balanced set of measures around the bifurcation points of the

River Rhine that maintains the discharge partitioning and has a maximum contribution to flood safety.

Starting point is a measure at the river IJssel (one of the Rhine bifurcates) just downstream the second

bifurcation point which had a large hydraulic effect that could not be compensated by the control struc-

tures. Stakeholders are, however, in favour of this measure, because it creates attractive opportunities

for the society, such as the development of nature and stimulate recreation. Re-examining the surround-

ing flood plains upstream the bifurcation point revealed options to balance the discharge partitioning.

However, this could only be done by simultaneously downsizing the effect of the original measure. This

was possible because the measure consists out of several distinctive parts. Not lowering a specific weir

in the project-area, did not affect the overall character of the measure (it was just as attractive) but

reduced the hydraulic effect by 50 %. The final result of the planning exercise was that it proved to be

possible to create a balanced set of measures that reduced the flood levels substantially, added to the

nature- and recreational values of the areas and yet maintained the discharge ratio at the bifurcation

points. The study also provided additional insight in the dynamics of both regulation works and their

impact on medium discharge ranges, and initiated some preliminary discussions whether this system can

be maintained for the far future when even more extreme discharges are expected.

Keywords: river bifurcation, river management, hydraulic effect


109



Recalculation of historical streamflow series. Impact assessmentand valorization.

Arnaud Belleville ∗† 1, Damien Sevrez 1

1 EDF - Division Technique Generale (DTG) – 21 avenue de l’Europe 38040 Grenoble cedex – France

For safety reasons, energy production or regulation, water resources management is one ofEDF’s (Electricite de France) main concerns. To meet these needs, since the fifties EDF-DTG(Division Technique Generale) has operated a hydrometric network that includes more than 350hydrometric stations. The process of producing streamflow series involves a succession of steps:acquisition of raw water level data, validation of these data, gauging operation, tracing of therating curve, discharge calculation, criticizing and data banking.The archiving of a discharge time serie into a database after the validation and criticizing phaseis often considered by the field hydrologist as the final step in the data production process.However, during the subsequent valorization of these data in the context of hydrological studies(calibration of hydrological models, flood forecasting and warning, engineering design, etc.), newknowledges relating to the hydrometric station (high-flow gauges, hydraulic modeling, etc.) maybe available and lead to the need to update discharges via the updating of the rating curves.Similarly, a historical succession of different practices of field hydrologists highlights heterogene-ity in the data processing.The paper proposes a methodology to update historical streamflow time series, so as to proposehomogeneous and less biased series. The GesDyn method [Morlot et al, 2014], is used to recal-culate streamflow series from water level records and historical gaugings. Otherwise, in orderto improve understanding of the hydraulic and extrapolation of rating curves for high flows,EDF-DTG has realized a major program of survey and hydraulic modeling for its hydrometricstations network.This methodology is then applied to an hydrometric stations sample. Two streamflow series arethen available for each station: the historical series and the recalculated series. The deviationsbetween the two series are analyzed through the following hydrological metrics: volume, low-flowfrequency distribution and high flow frequency distribution. A case study is finally detailed tohighlight the potential impacts of streamflow time series recalculation on the determination ofextreme flows.In terms of perspectives, a reflexion can be made on the role of the field hydrologist in relationto the hydrologist using these data, on the interest of inscribing these recalculations of streamflow series in a perennial and systematic approach. The question of the valorization and thetraceability of such studies is also asked.

Keywords: Rating curve, extrapolation, streamflow time series


110



Experimental and numerical analyses on the capacity and thecontrol management of a large flood retention basin situated at

the Inn River in Tyrol

Adrian Lindermuth ∗† 1, Bernhard Gems 1, Stefan Walder 2, Markus Aufleger 1, IrinaKampel 2, Christoph Waldhoer 2

1 Unit of Hydraulic Engineering, University of Innsbruck, 6020 Innsbruck – Austria2 Dept Water Management, Office Tyrolean Regional Government, 6020 Innsbruck – Austria

Between the 20th and 23rd of August 2005 a pronounced depression across the Gulf of Genoa led to

large amounts of precipitation in the Alpine region. In the western federal provinces of Austria rainfall

intensities of more than 20 mm/h and accumulated amounts of around 280 mm within 48 hours were

registered. On these days, the Tyrolean Inn reached in the area of the capital city Innsbruck, a flood

peak, which corresponded to a 200-year flood event and caused damage totaling 350 million euros. A

considerable proportion of these massive flood damages also occurred in the tributary rivers, mainly

affecting the valley floors of Rosanna and Trisanna River. The consideration of recent extreme events

in flood statistics implies an increase of design floods such as the 100-year flood peak. Potential con-

sequences are an enlargement of flooded areas, of affected settlement areas, as well infrastructure and

traffic facilities. Concerning land use management and construction regulations for buildings, changes in

the zoning of hazard maps play an important role. With the focus on the 75 km long Tyrolean Inn River

downstream the capital city Innsbruck, the harmonization of the 100-year flood peak and appropriate

results of 2d-hydrodynamic modelling simulations indicate the need for extensive construction measures

to protect the vulnerable settlements and industrial areas situated closely to the River. Linear protection

measures, representing the only feasible option in the confined area conditions, lead to an increase of the

peak discharge and would demonstrably worsen the situation for downstream areas. In order to counter

this impact, three large areas along the river with capacities up to 5.4 million cubic meters are planned to

be build. A controlled flooding of these areas is realized with a set of adjustable gates at the inlet struc-

tures. The present study deals with the efficiency and control management of one retention area situated

in the Lower Inn Valley. For it, a physical scale model test was accomplished in the hydraulic laboratory

at the University of Innsbruck. The model scale is 1:35 according Froude similarity. The inlet structure

contains four weir fields, each equipped with an adjustable primary and a secondary vertical gate. The

experiments mainly focus on the determination of the performance of the weir fields as a function of the

water levels in the receiving water and in the retention area. Operation modes with single and combined

use of weir fields are analyzed. The maximum discharge capacity of the inlet structure is determined

and important parameters for an optimum use of the retention area in case of extreme flood events (e.g.

operation interval, location of control gauge in the Inn River) are evaluated. Further, extraordinary loads

in terms of a 300-year flood event, intense bed-load and driftwood accumulation in close range of the

inlet structure and as well potential influences of bed-level changes in the Inn River are tested. Apart

from an almost horizontal riverbed, a tributary in the immediate vicinity of the building creates a special

challenge during model construction and experiments, but also for the operation in practice. Concerning

installed measurement devices, water inflow takes place via several lines and is controlled electronically

via hydraulic flaps and inductive discharge measurements. Fixed and mobile ultrasound gauges are used

to determine the flow depths. The flow velocities are recorded using micro impellers and a Vectrino sen-

sor. Retained discharges are controlled via a Poncelet-weir, which is arranged directly after the retention

area.

The experimental modelling results confirm the aspired effects of the considered retention area in com-

bination with the remaining flood protection and retention measures in the Lower Inn Valley. With an


111



optimal control management of the retention area inlets, a 100-year design flood event is coped without

flooding settled areas on the valley floor and a 300-year flood does not cause any relevant damages on

buildings, infrastructure and traffic facilities. Analyses of the extreme loading scenarios reveal a robust

arrangement of the considered inlet structure in terms of clogging scenarios and sedimentation. With

careful management of the retention areas, various hydrological extreme events can be managed with

characteristics (spatial and time-varying) features which differ from those of the design flood event.

Keywords: Flood Protection, Flood Retention, Physical Scale Model, Inn River

112



14:00 – 15:40

BC 5 – Experimental hydrodynamics – part 2 . . . . . . . . . . . . . . 114

Me 5 – Dams and reservoirs – part 1 . . . . . . . . . . . . . . . . . . . 119

Li 5 – Bedload measurements . . . . . . . . . . . . . . . . . . . . . . . . 125

Br 5 – Urban floods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

113


Comparison of velocity and turbulence profiles obtained with aVectrino Profiler and PIV

Jay Lacey ∗† 1, Jason Duguay 1, Bruce Macvicar 2

1 Department of Civil Engineering, Universite de Sherbrooke – Canada2 Department of Civil and Environmental Engineering, University of Waterloo – Canada

Laboratory experiments were carried out in a small open-channel hydraulic flume at theUniversite de Sherbrooke. A PIV and an acoustic Doppler velocity profiler (Vectrino II (VII))were used to measure high frequency velocities in profiles along the centreline of a small open-channel flume. Two background turbulence levels were tested. Comparisons were made ofmean and turbulent statistics obtained with the two measurement techniques. The results showreasonable agreement between mean streamwise and lateral velocities measured with the PIV andVII near the ”sweet spot” of the VII. In contrast, mean vertical velocities deviate substantiallybetween the two measurement methods. Turbulence statistics have somewhat similar profileshapes, yet significant bias is observed between the two measurement methods.

Keywords: Instrumentation, velocity profiles, turbulence statistics, Vectrino Profiler, PIV


114



Experimental study of the surface oscillations induced by ashallow flow past a lateral cavity

Lukas Engelen ∗† 1, Stephan Creelle 1, Laurent Schindfessel 1, Tom De Mulder 1

1 Hydraulics Laboratory, Dept. of Civil Engineering, Ghent University – Belgium

The interaction between a rectangular, open channel, lateral cavity and a shallow mainstream gives rise to one or multiple recirculation cells within the cavity (Riviere et al., 2010)and vortex shedding in the mixing layer between the cavity and main stream (Mignot et al.,2016). For certain combinations of geometry and flow characteristics, standing gravity wavesare excited within the cavity that oscillate at its natural frequency (Wolfinger et al., 2012; Tunaet al., 2013). Tuna and Rockwell (2014) and Mignot et al. (2015) showed that the water surfacewithin the cavity can start to oscillate in the longitudinal or transverse direction, and even bi-directional seiching has been reported. However, the conditions in which the different seichingmodes occur and their (possible different) effect on the flow field is not yet fully understood.Because this ‘seiching’ phenomenon alters the flow field and mass exchange processes, funda-mental experimental research is needed to understand and predict its occurrence.The paper presents an experimental study in which the standing gravity waves inside the cavityare reconstructed. First, the occurrence and relative magnitude of the different seiching modesare quantified for a range of flow conditions using two simultaneous pressure registrations inthe corners of the cavity. Although previous research showed that the possible frequency of thecavity oscillations can be estimated based on the cavity’s geometry and water depth, no methodhas been found to predict when and which mode will be triggered. The presented comparisonof the relative magnitude of the seiching modes suggests that a transitional Froude numberexists, approximately 0.63, at which the dominant seiching mode changes from transverse tolongitudinal seiching. Moreover, the relative amplitude of longitudinal seiching proved muchmore significant than that of transverse seiching.Secondly, two flow configurations with dominant seiching in either the transversal or longitudi-nal direction are selected based on the pressure-based results, for which the surface variation isanalyzed in detail using a recently developed 3D-PTV setup. By seeding the flow with float-ing particles, their instantaneous positions are combined to reconstruct the time-dependent 3Dsurface inside the cavity. Although the technique is still being optimized, the preliminary re-sults in this paper seem to confirm the multi-modal and bidirectional aspect of the seichingphenomenon. Especially in case of dominant transverse seiching (Fr< 0.63), the surface seemsto be the superposition of multiple seiching modes.Further research will focus on the improvement of the 3D-PTV setup to achieve better andmore robust results. Subsequently, 3D-PTV will be used to analyze the surface oscillations evenmore in detail, but also use the Lagrangian information to study the (3D) flow field and massexchange between the main stream and cavity.

Keywords: Open channel flow, lateral cavity, seiching, water surface reconstruction, surface PTV,

resonant coupling


115



Predicting the vortex shedding frequency at the interface oflateral cavities

Clement Perrot-Minot ∗† 1, Emmanuel Mignot 1, Nicolas Riviere 1, Richard Perkins 1

1 Laboratoire de Mecanique des Fluides et d’Acoustique (LMFA) – Ecole Centrale Lyon, Univ. C.Bernard Lyon 1, INSA Lyon, CNRS UMR5509 – 36 Av Guy de Collongue 69134 Ecully cedex – France

In river environments, lateral cavities are typical simplified versions of by oxbow lakes,artificial harbors, wandos, etc. The behavior of the free surface in such cavities is found tobe strongly dependent on the Froude number of the main stream. Observations reveal thatfree surface oscillations in these lateral cavities, named ”seiche”, occur for a Froude numberabove Fr=0.6, and can attain large amplitude (up to few meters) with relatively short period( ˜10min). The origin of these oscillations is often attributed to a resonance of vortices shed inthe mixing layer (at the interface between the cavity and the main flow) with one of the naturalfrequency of the cavity.However for a Froude number below Fr=0.6, free surface oscillations in the cavity are of muchsmaller amplitude. Predicting the vortex shedding frequency in the mixing layer between acavity and a main stream could help predicting the apparition of the seiching phenomena butalso the momentum and mass exchange between the cavity and the main flow. Hence, the vortexshedding frequency is examined experimentally in absence of large oscillation of the free surfaceinside the cavity, i.e. for Fr < 0.6.It was observed that the vortex shedding frequency follows monotonically increasing trends withincreasing Froude number of the main stream, with possible jumps from one to another.These trends are retrieved analytically by adapting to the present configuration a model basedon the Rossiter approach. This model considers that the vortices shed in the mixing layercreate some water depth variation at the impingement corner of the cavity, in turn generatingpressure waves that propagate upstream, and influence the vortex shedding process. Finally, themeasured vortex shedding frequencies correspond quite accurately to the frequencies predictedby the model. This highlights the existence of a resonant phenomenon between vortices in themixing layer of a lateral cavity and gravity waves even without any seiching phenomena.

Keywords: Seiche, resonnance, lateral cavity, mixing layer


116



Advanced characterization techniques of the scour hole arounda bridge pier model

Ana-Margarida Bento ∗† 1, Lucia Couto 2, Joao Pedro Pego 1, Teresa Viseu 2

1 Laboratorio Nacional de Engenharia Civil / Faculdade de Engenharia da Universidade do Porto(LNEC / FEUP) – Portugal

2 Laboratorio Nacional de Engenharia Civil (LNEC) – Portugal

The collapse of bridges may occur due to several reasons, being local scouring around itsfoundation the most common in both national and international contexts. Local scour occursdue to the formation of vortices around obstacles (piers or/and abutments) as a result of chang-ing the unidirectional approach flow into the three-dimensional field in an erodible channel (asa riverbed). The local scouring process is, thus, intrinsically dependent on bridge geometry,river channel morphology, and hydrologic regime, which are entirely site specific. The study ofthe individual contribution of each parameter will provide mechanisms and improved tools tominimise the occurrence of such catastrophic failures, as well as the inevitable and subsequenteconomical losses and human casualties. These widespread and serious threats have increasedthe awareness of and interest in bridge scour research until our days.One of the most intuitive mean of studying the scouring phenomenon and with significant ad-vances over decades is physical modelling. Therefore, the goal of this work is to characterize thescour hole development in time due to the presence of a bridge pier model in a movable bed andto discuss the inherent hydrodynamic erosion processes.To accomplish this objective, local scouring experiments, reproducing the flow at the vicinityof a bridge pier model embedded in a uniform sediment bed, were performed in the 40.7 mlong, 2.0 m wide and 1.0 m deep glass-sided rectangular tilting flume (CIV), located at LNEC,Lisbon (Portugal). The bridge pier model does not reproduce a specific bridge pier, but itsdesign replicates the typical shape of bridge foundations of the XIX and XX centuries, whichare the most common in Portugal. The 0.14 m thick rectangular round-nose concrete columnwas installed at the middle cross section of an existing recess box and covered with a uniformquartz sand characterized by a mean sediment diameter (D50) of 0.86 mm, a specific gravity(s) of 2.65, and a geometrical standard deviation (σD) of 1.28. The sand adopted, the positionand the geometrical characteristics of the bridge pier were chosen in order to avoid the sand bedgradation effect, and the flume sidewall effects on the scouring process.In the present work, the characterization of the scour hole geometry took advantage of ad-vanced survey and sensor technologies, which have been replacing the topographic informationretrieved from traditional cross-section models by the three-dimensional (3D) point clouds anddigital elevation models. (DEMs). Kinect sensor and close-range photogrammetry offer efficienttechniques of deriving point clouds and DEMs, respectively, and were both applied in this study.Their potential, limitations and results are herein examined and conveniently compared.

Keywords: bridge pier, photogrammetry, experiments, kinect sensor, scour hole, sediment transport


117



Flow distribution in diverging compound channel usingimproved independent subsection method

Bhabani-Shankar Das ∗† 1, Kamalini Devi 1, Sebastien Proust 2, Kishanjit K. Khatua 1

1 Civil Engineering Department, NIT Rourkela, Odisha, India, India2 Irstea centre de Lyon-Villeurbanne, UR RiverLy – 5 rue de la Doua, CS 20244, 69625 Villeurbanne

cedex – France

Experiments have been conducted in three diverging compound channels for different flowconditions to study the flow distributions in floodplain, upper and lower main channel. Ina compound channel, vertical apparent shear exists on the interface between the upper mainchannel and the floodplain, which generally accelerates the flow on the floodplain and resists theflow in the upper main channel. In addition, a horizontal apparent shear stress also occurs onthe interface between the upper and lower main channels, which generally accelerates the flowin the lower one and resists the flow in the upper one. Therefore, it is essential to consider theexchanges of momentum at both vertical and horizontal shear layer regions. In this paper, anattempt is made to improve the classical independent subsection method (ISM) to determine themagnitudes of flow and velocities in both upper and lower main channels. Four subsections arecreated in improved ISM according to the vertical and horizontal division lines that correspondto the vertical interface between the main channel and floodplain and the horizontal interfacebetween upper and lower main channels respectively. The improved ISM consists in a set offour coupled 1D momentum equations (instead three equations of classical ISM) for subsectionsand a mass conservation equation for the total cross-section. The computed results show thatthe method is well capable of predicting the discharge distributions in the floodplain and mainchannel (both at upper and lower main channel).

Keywords: Flow distribution, diverging compound channel, upper and lower main channels, ISM


118


Thursday 6 September, 14:00 – 15:40 Me 5 – Dams and reservoirs – part 1

Numerical study on reservoir sediment management by addingexcavated sediment downstream of dams in Japan

Sameh Kantoush ∗† 1, Takamasa Suzuki 2, Yasuhiro Takemon 1, Kamal El kadiAbderrezzak 3, Riadh Ata 3, Tetsuya Sumi 1, Mohamed Saber 1

1 Water Resources Research Center, Disaster Prevention Research Institute, Kyoto University – Japan;2 Shizuoka Prefectural Government, Shizuoka – Japan;

3 Laboratoire d’Hydraulique Saint-Venant – 6 quai Watier, BP49, 78401 Chatou cedex – France

In Japan, there are more than 2700 operating dams, more than 15 m in height with median age of 61

years. Among them, 900 dams have reservoir volumes larger than 1.0 Mm3. Japan is a world leader in

the number of implemented sediment management techniques by flushing, sluicing, dredging/excavating,

and bypassing. Excavating sediments and transporting them to the reach just below the dam, where

natural or artificial floods will distribute them along the riverbed, such technique has different definitions

and classifications. Sediment supply tests have been conducted in more than 20 dams in Japan managed

by Ministry of Land, Infrastructure and Transport (MLIT). In such tests of these dams, the sediment

is transported temporarily below dams and flushed by the natural or artificial released flow. Sediment

transport and associated channel mobility are recognized as key processes for creating and maintaining

physical habitats, aquatic and riparian ecosystems in the river basin scale. However, the effect of sup-

plied sediment on the bed elevation, sediment size and habitat in the supplied river segment has not been

studied well because of the the limited sediment volume in most of Japanese dams.

The paper summarizes various case studies on excavated sediment supply in Japan and a case of nu-

merical study to evaluate the effect of the supplied sediment on the spawning redds of Ayu- fish in the

Tenryu River. Detailed monitoring of pre- and post- sediment supply are carried out to analysis the

impact of such technique on riverbed formation, riverbed materials, benthic organisms, and algae. As

sediment supplied projects have different configurations of flow and sediment characteristics, some of

these projects had positive impacts when supplied sediments are washed during high flows. On the other

hands, some cases induced undesirable morphological and ecological consequences as well as significant

channel adjustments that result in failure of the restoration project itself.

Results of numerical simulations show that under the present management scheme of non-supplied sedi-

ment from the upstream dams, suitable spawning redds are formed on sandbars at the confluence instead

of riffles. However, field surveys indicate that riffles with newly deposited sediment are more suitable for

fish spawning. The effects of sediment supplies on the spawning environment for Ayu-fish were investi-

gated via a review of past field studies at the Tenryu River. Newly formed riffles with gravel substrates

were evaluated to be suitable for Ayu-fish spawning redds. Investigations to predict potential spawning

areas using two-dimensional numerical modelling revealed that under the present management scheme of

not supplying sediment from the upstream dam, suitable spawning redds would be formed not on riffles

in the main channel, but on riffles in the secondary channel at the confluence with the main channel.

Future projects include simulations to determine the impact of sediment supply conditions (i.e., loca-

tion, quantity, etc.) on the number of soft riverbeds. Additionally, a more detailed investigation on the

relationships between the formation of water channels on sandbanks and riverbed softness, which were

investigated herein, will offer insight on the formation of Ayu-fish spawning redds due to the sediment

supply and flow rate during floods.

Keywords: River restoration, Sediment transport, Sediment replenishment, 2D numerical model,

Habitat restoration downstream of dams


119



Numerical modelling of bank failures during reservoirdraw-down

Nils-Reidar Olsen ∗† 1, Stefan Haun 2

1 The Norwegian University of Science and Technology (NTNU) – Norway2 University of Stuttgart – Germany

Numerical algorithms are presented for modeling bank failures during reservoir flushing.The algorithms are based on geotechnical theory and the limit equilibrium approach to findthe location and the depth of the slides. The actual movements of the slides are based on thesolution of the Navier-Stokes equations for laminar flow with high viscosity. The models areimplemented in the SSIIM computer program, which also can be used for modelling erosion ofsediments from reservoirs. The bank failure algorithms are tested on the Bodendorf hydropowerreservoir in Austria. Comparisons with measurements show that the resulting slides were in thesame order of magnitude as the observed ones. However, some scatter on the locations wereobserved. The algorithms were stable for thick sediment layers, but instabilities were observedfor thin sediment layers.

Keywords: Navier, Stokes equations, sediment transport, resevoir flushing, geotechnical failure


120



Design optimization of permeable sediment traps for fluvial bedload transport.

Anita Roth ∗† 1, Sebastian Schwindt 2, Mona Jafarnejad 1, Anton J. Schleiss 1

1 Ecole Polytechnique Federale de Lausanne (EPFL) – Switzerland2 UC Davis – United States

Sediment traps are crucial elements for flood protection in mountain rivers with high sedi-ment transport capacity. Existing structures often interrupt the channel connectivity. Ideally,a sediment trap should be permeable for bed load during non-hazardous floods and ensuresediment retention during hazardous discharges. A new sediment trap concept, fulfilling theserequirements was recently developed and tested in a laboratory flume. A guiding channel troughthe deposition area is combined with a slot check dam having an upstream bar screen with bot-tom clearance. This study aims to validate the proposed concept with a finer sediment mixtureon an experimental set-up. Furthermore, we provide improved recommendations for bar screendesign regarding minimal bar spacing and the range of applicable clearance heights. Optimal barspacing and clearance heights of the bar screen are determined through individual tests of thebar screen with steady discharges and varying sediment supply intensity. The best performingbar screen configuration is subsequently tested in combination with a slot check dam using aflood hydrograph to simulate the influence of quasi-unsteady discharge. The proposed conceptcorresponds to a combined mechanical-hydraulic control and works well for a large range of grainsizes, if the bar screen is correctly adapted.

Keywords: Open check dams, Permeable sediment trap, River continuity, Sediment retention, Bed

load


121



Three-dimensional numerical modeling of hydraulics andmorphodynamics of the Schwarzenbach reservoir

Kilian Mouris 1, Felix Beckers 1, Stefan Haun ∗† 1

1 University of Stuttgart – Germany

Three-dimensional numerical modeling has become particularly important in hydraulic engineering

during the last decade. One reason is that the application of one- or two-dimensional numerical models

is in many cases, for instance in modelling reservoirs, not satisfying due to complex occurring three-

dimensional flow fields. Especially in morphodynamic modeling, e.g. to predict sedimentation processes,

it is essential to take these three-dimensional effects into account. Therefore, in this study the numerical

model SSIIM 2 was used to simulate the flow situation, the suspended sediment transport and the sedi-

mentation processes within the Schwarzenbach reservoir in Germany.

The Schwarzenbach reservoir is located in the northern Black Forest, has a length of 2.2 km, a maximum

width of 600 m and a maximum depth of 47 m at operation level leading to a total storage capacity of

14.4 million m3. The reservoir was built in 1926 to serve as upper reservoir in a hydro-electric pump

storage system. It has a complex flow field induced by three natural tributaries fed by a catchment area

of 50 km2 (two surface inflows at the head and one transition tunnel in the middle of the reservoir) and

the additional pumped and turbined water.

For the numerical investigations the 3D model SSIIM 2 is used. SSIIM 2 has been successfully applied in

previous studies to model suspended sediment transport and depositions in reservoirs. The model uses

an unstructured, non-orthogonal and adaptive grid, which allows the grid to move with changes in the

bed and water levels. The computation of sediment transport is divided into suspended and bed load

transport. Suspended sediments are calculated by solving the transient convection-diffusion equation and

bed load transport is calculated by an empirical formula.

Hydrodynamic simulations were carried out in a first step to assess the influence of different algorithms

and parameters on the calculated flow field. Among these are simulations to test the effect of wind, differ-

ent turbulence models and different discretization schemes (Power Law, Second Order Upwind, QUICK,

Van Leer). All simulations show a complex flow field with two large (re-)circulation zones in the middle

of the reservoir, mainly as result of the inflow from the transition tunnel (lateral inflow). Thereby, the

influence of wind and the different discretization schemes on the size and location of (re-)circulation zones

could be seen.

To assess the performance of the model, a plausibility check was performed based on stationary ADCP

measurements from 2016. The ADCP was installed in an upward-looking configuration on the bottom of

the reservoir approximately 270 m northwest from the operation outlet. Comparisons illustrate compa-

rable patterns and characteristics. However, the numerical model underestimates the velocity magnitude

during pumping and turbine operation.

Morphodynamic simulations were carried out in a second step to compute the suspended sediment dis-

tribution and to investigate deposition patterns within the reservoir. Five different grain fractions were

implemented in the model. The grain diameters correspond to sediment samples taken from the reservoir

bed in 2016. Nine scenarios were simulated, which differ in terms of water level and inflow conditions as

well as in the used upwind schemes and in taking into account the wind. The results of the morphody-

namic simulations demonstrate that the suspended sediment distribution and the deposition pattern are

mainly influenced by the inflow discharge and the operation level of the reservoir. Modified discretiza-

tion schemes or a consideration of wind had almost no influence, neither on the suspended sediment

concentration pattern nor on the sediment depositions.


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Keywords: 3D numerical modeling, RANS model, sediment transport and deposition, reservoir

management

123


Sediment balance of a cascade of alpine reservoirs based onmulti-decadal data records

Sebastian Guillen-Ludena1 ∗† , Pedro A. Manso1 , Anton J. Schleiss1 , Benno Schwegler2

, Jan Stamm2 , Andres Fankhauser2

1 Laboratoire de Constructions Hydrauliques, Ecole Polytechnique Federale de Lausanne, Switzerland(LCH-EPFL) – EPFL-ENAC-IIC-LCH Station 18 CH-1015 Lausanne – Switzerland

2 KWO Kraftwerke Oberhasli AG, Grimselstrasse 19 CH-3862 Innertkirchen – Switzerland

Reservoir sedimentation is a major concern in the operational management of dams andappurtenant structures. The increasing volume of sediments deposited in reservoirs leads to aloss of water storage, undermining the purpose itself of the dam for human use or protection.The deposition of sediments (mostly fine) in the vicinity of the dam’s operational structures, suchas bottom outlets and power intakes, may result in partial or total blockage of these structures.To cope with these problems, it is essential to determine the sediment balance of the reservoirs,by assessing the origin and quantity of the in- and out-fluxes of sediments. This paper presentsa methodology to determine the annual sediment balance of a system of interlinked reservoirsacross several decades, as well as its application to the alpine hydropower cascade formed bythe Oberaar, Grimsel and R’aterichsboden reservoirs located in Switzerland. At that aim, theannual sediment fluxes and the sedimentation rates of each reservoir were characterized. Also,the percentage of fine sediments (dm < 10 µm) included in the total sedimentation rate wasestimated. The results reveal that the annual sedimentation rate of the lowermost reservoirof the system (R’aterichsboden) is highly altered by the flushing operations of the reservoirupstream (Grimsel). Also, for the uppermost reservoir of the system (Oberaar), the volume offine sediments deposited annually can reach up to 46% of the total sedimentation rate.

Keywords: Reservoir sedimentation, Sediment balance, Cascade, Fine sediments


124


Thursday 6 September, 14:00 – 15:40 Li 5 – Bedload measurements

Experimental bed active layer survey with active RFID scourchains: Example of two braided rivers in the French Alps (the

Drac and the Veneon)

Guillaume Brousse ∗ 1, Gilles Arnaud-Fassetta † 1, Frederic Liebault 2, DanielVasquez-Tarrio 3

1 Pole de Recherche pour l’Organisation et la Diffusion de l’Information Geographique (PRODIG) –CNRS UMR8586 - 2 rue Valette - 75005 Paris – France

2 Irstea centre de Grenoble, UR ETNA – 2 Rue de la Papeterie, 38402 Saint-Martin-d’Heres – France3 Centre Europeen de Recherche et d’Enseignement de Geosciences de l’Environnement (CEREGE) –

CNRS UMR7330 – avenue Louis Philibert - BP 80 - 13545 Aix-en-Provence cedex 4 – France

An innovative scour chains device composed of active UHF RFID tags is proposed to surveythe bed active layer. This device has been tested on three cross-sections deployed along two largealpine braided rivers: the Drac and the Veneon rivers. A specific field deployment procedurehas been developed, using a technique of drilling with a tube and a jack-hammer. After eachflood, the device allows to record presence or absence of active tags inside a 1-m deep scourchain column. This provides the maximum scouring depth of the bed at the position of thecolumn, and the topographic resurvey of the channel provides the net fill depth. The mainadvantage of this technology against traditional scour chains is the rapidity and easiness withwhich the scouring depth is obtained after a flow event, notably under conditions of massive netdeposition after the flow. Another key benefit is the very high recovery rate of immobile tags,which secures the reconstruction of the active layer, even after extreme floods. This technology istherefore particularly suitable for large braided rivers, where traditional scour chains necessitatetoo much field efforts for their relocation, and can be rapidly lost under deep active layers. Evenif active RFID scour chains are much more expensive than traditional scour chains, our fieldtesting demonstrate that they provide a very robust solution for the reconstruction of the activelayer under the challenging field conditions of very active and large braided channels. RFIDerosion columns provided new data on the active layer of the studied streams. After differentflow events, including a major flood on the Veneon, we recorded a mean bed active layer of1.2 m in the Veneon River and 0.25 m in the Drac River. Important standard deviations areidentified along cross sections (0.2 m on the Veneon River and 0.3 m on the Drac River). Thesevariations are explained by bedload magnitude, which is controlled by. In prospects, erosioncolumns opens the way to coupling bed active layer monitoring and bedload tracking within asingle device.

Keywords: Bed active layer, scour chains, active UHF RFID.


125



Application of the wavelet transform to sediment grain sizesanalysis with an impact plate for bedload monitoring in

sediment bypass tunnels

Takahiro Koshiba ∗† 1, Tetsuya Sumi 1

1 Water Resources Research Center, Disaster Prevention Research Institute, Kyoto University – Japan

An impact plate (IP) is a bedload transport monitoring device developed for a part of thesediment bypass tunnels management. In the measurement, the impact produced by bedload isrecorded as the number of impulses (Ip) which is widely used in Japan. Ip, however, has severalshortcomings attributed to the insufficient raw signal denoising. In this study, the discretewavelet transform (DWT), an advanced signal processing technique especially for noisy, non-periodical, and transient signals, was introduced to devise an improved Ip count system solvingthe problems in the original signal denoising process. The presented results revealed that theDWT is useful for water noise reduction, signal overlap reduction, and mitigating Ip saturationat grain sizes Ds = 50 and 100 mm compared to the original Ip counting system.

Keywords: Impact plate, Bedload monitoring, Wavelet transform, Sediment bypass tunnels, Grain

size


126



Measuring bedload grain size distributions with passive acousticmeasurements

Thomas Geay ∗† 1, Sebastien Zanker 2, Teodor Petrut 1, Alain Recking 3

1 GIPSA-lab, Univ. Grenoble Alpes, CNRS, Grenoble INP – 38000 Grenoble – France2 EDF - Division Technique Generale (DTG) – 21 rue de l’Europe - 38040 Grenoble cedex – France

3 Irstea centre de Grenoble, UR ETNA – 38041 St-Martin-d’Heres – France

Bedload Self-Generated Noise (SGN) measurements consist in deploying an underwater mi-crophone (i.e. a hydrophone) in the water course and to record the ambient noise of a river.The use of hydrophones is of interest as it can be easily deployed and can provide a continuousmonitoring of bedload transport. However, developments are still required to fully understandhow bedload characteristics (e.g. specific flux or granulometry) are related to bedload SGN pa-rameters (e.g. acoustic power and spectrum). Laboratory experiments have shown that centraland peak frequencies of bedload noise decrease as the particle size increases, just like in stringinstruments where the tone frequency decreases from a narrow string to a broader string. In thispaper, we propose to test a new inverse method enabling the estimation of bedload grain sizedistributions from SGN measurements. The inverse method is based on a theoretical modellingof the noise generated by a bedload mixture. SGN and physical sampling measurements havebeen made in 5 French alpine rivers having several transport conditions (bedload D50 from 1to 40 mm) and varying slopes (0.05 to 1%). Measurements were made for specific bedload fluxvarying from 10 to 150 g/m/s. The proposed inverse method was used to estimate the bedloadgrain size distributions. SGN results are compared to bedload samples and are found to largelyoverestimate sampled granulometries. Finally, it is observed that the spectral characteristicsof bedload SGN are not related to bedload GSD but rather to the roughness of the river bed,acting as a source of attenuation and shaping bedload SGN spectra.

Keywords: bedload monitoring, surrogate methods, hydrophones, grain size distributions, granu-

lometry, passive acoustic


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An estimate of bedload discharge in rivers with passive acousticmeasurements: towards a generalized calibration curve.

Sebastien Zanker ∗† 1, Thomas Geay 2, Alain Recking 3,4, Alexandre Hauet 1, ClementMisset 3,4

1 EDF - Division Technique Generale (DTG) – 21 rue de l’Europe - 38040 Grenoble Cedex France2 Grenoble Images Parole Signal Automatique (GIPSA-lab) – Universite Grenoble Alpes, 11 rue des

Mathematiques, 38402 Saint-Martin-d’Heres cedex – France3 Universite Grenoble Alpes – 38041 Grenoble – France

4 Irstea centre de Grenoble, UR ETNA – 38041 St-Martin-d’Heres – France

Bedload Self-Generated Noise (SGN) measurements consist in deploying an underwater mi-crophone (i.e. a hydrophone) in the river and to record the ambient noise. The use of hy-drophones to measure bedload characteristics (flux, spatial distribution, granulometry) couldbe of interest as it can be more easily and rapidly deployed than physical samplers in rivers.Several measurement campaigns where conducted during spring and summer 2017 in 5 alpinerivers with contrasted transport conditions (bedload D50 between 1 and 40 mm) and varyingslopes (0.05 to 1 %).Physical sampling measurements were done from a bridge along the river cross section for specificbedload flux varying between 10 and 150 g.m-1s-1. Bedload SGN measurements were obtainedwith a small board equipped with a hydrophone and deriving downstream the bridge within a10 to 50 m long river section. For 2 of the 5 rivers, acoustic Doppler current profilers (ADCP)were also deployed along the river cross-section to provide a surrogate measurement of apparentbedload velocity.As a result, we have been able to draw an acoustic 1D-map of the river bottom, derived fromthe SGN sub-surface measurements obtained with the deriving board. The results show a co-herent relation between the riverbed acoustic maps and the physical samplings for 3 rivers over5. Bedload profile were less consistent with SGN measurements when bedload transport waslocalized in a narrow channel. The apparent bedload velocities obtained with ADCP for 2 riversare consitent with the physical samplings (bedload location and flux distribution) but a slightbias was observed and is attributed to grain-size sorting effects along the cross-section.Finally, when plotting together 4 over 5 rivers, an almost linear relation can be establishedbetween bedload discharge (computed with physical samplings data) and the average acousticresponse (i.e acoustic power averaged over the cross-section). This result suggests that a gener-alized calibration curve could exist between bedload SGN and bedload discharge. The existenceof an outsider is interpreted as a problem related to propagation effects. Further researchesshould therefore concentrate their effort on deconvoluting SGN signals from propagation effectsto give a better confident proxy for bedload discharge measurement in different rivers types.

Keywords: Bedload, Measurement, Acoustic, Hydrophone, Helley, Smith, ADCP


128



On bedload measurement performances of high-resolutionacoustic (ACVP) and conductivity (CCP) profilers

Guillaume Fromant ∗† 1, Ryan Mieras 2, Thibaut Revil-Baudard 1, David Hurther 1,Jack Puleo 2, Julien Chauchat 1

1 Lab. Ecoulements Geophysiques Industriels (LEGI) – BP 53 38041 Grenoble cedex 9 – France;2 Center for Applied Coastal Research, Dept Civil and Env. Eng., Univ. Delaware – United States

Over the past two decades, considerable research efforts have been concerned with understanding

and modeling sediment transport processes under energetic flow forcing conditions for which bedload

moves as a sheet flow. In this context, it is widely accepted that the geophysical community suffers from

a technological lack of high-resolution flow measurement tools adapted to the study of sediment trans-

port physics in environmental flows. The ability to profile sediment transport across the entire bottom

boundary layer over a mobile bed is currently limited to a few measurement technologies, due to the

extremely high particle concentration (0.08 < φ < 0.35) and limited vertical thickness (of the order of

the particle size) of the bedload layer. This strongly limits our advance in process based modeling of

sediment transport, especially concerning the validation and optimization of two-phase modeling that

require advanced high-resolution measurement tools capable of sediment flux profiling at turbulent flow

scales across the bedload layer.

This study reports on detailed measurements of particle concentration and velocity profiles under gravity-

current driven sheet flow conditions involving two fundamentally different measurement systems: an

acoustic concentration and velocity profiler (ACVP) and two types of conductivity concentration profil-

ers (CCP), distinguished by their vertical sampling resolution (1 mm versus 2 mm). The objective of

this study lies in the evaluation of the measurement performances (and limitations) of the two systems

in retrieving the bedload layer properties.

Tests were conducted using two different uniformly distributed acrylic particles having diameters of 1.0

and 3.0 mm, and a packed bed volumetric concentration of 0.55. The flow conditions were adapted to

each particle size to ensure similar sediment transport flow regimes as sheet flows, with a Shields num-

bers near 1 and a suspension number (ratio of settling velocity to friction velocity) near unity for the two

experiments. The two systems were used to measure instantaneous concentration profiles across the bed

load and suspension layers. This study marks the first use of the 2 mm CCPs, as well as it is the first

time the CCP technology is used in light-weight acrylic particle flows driven by steady, unidirectional

gravity currents.

A detailed comparative analysis of acoustic and conductivity-based measurements is carried out in terms

of measured concentration profiles, bed interface position of the flow bed and the sheet flow layer thick-

ness.

As expected from electric conductivity based measurement principle, the CCP technology provides very

accurate and sensitive concentration profiles over the entire dense sheet flow layer associated with

φ > 0.08. Its ability to return accurate concentration estimates in the dilute suspension layer down

to concentrations of the order of 1% and 10% for the 1 mm CCPs and 2 mm CCPs, respectively, is also

shown outside its conventional range of application usually restricted to φ > 0.10.

The ACVP provides reliable non-intrusive concentration estimates across the entire dilute suspension

layer, confirming the applicability of acoustic scattering based technologies to dilute sediment suspension

flows. Inside the dense bedload layer, very good agreements with the CCM measurements are found for

φ < 0.35 for the two tested conditions. In the lower dense bedload layer associated with the sediment

pick-up layer, systematic overestimations of the acoustic measurements are observed, comprised within

less than 10% of the CCM measurements.


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Finally, a good agreement is found between the three flow measurement systems in terms of average

and time-resolved bed level position and bed load layer thickness, validating the different bed interface

detection methods implemented in the two systems.

Keywords: Sediment transport, sheet flow, concentration measurement, ACVP, CCP

130

Thursday 6 September, 14:00 – 15:40 Br 5 – Urban floods

Study of dam break flow interaction with urban settlementsover a sloping channel

Ioanna Stamataki ∗† 1, Jun Zang 1, Eugeny Buldakov 2, Thomas Kjeldsen 1, DimitrisStagonas 2

1 Research Unit for Water, Environment and Infrastructure Resilience, University of Bath (WEIR) –Claverton Down Road, Bath, BA2 7AY – United Kingdom

2 Department of Civil, Environmental and Geomatic Engineering, University College London (UCL) –Gower Street, London, WC1E 6BT – United Kingdom

This paper describes a dam break experiment on a sloped channel, carried out in a hydraulicflume at UCL for the purpose of computer model validations of extreme events, such as flashfloods.An elevated reservoir was situated upstream followed by a 1/20 slope leading up to a flat flood-plain. Plexiglas blocks were positioned on the floodplain constituting different urban settlementsand creating different obstructions to the flow. The flume was instrumented along its lengthmeasuring the change in water depth in the reservoir; the water depth time histories in variouslocations; the flow patterns and flood front velocity; and lastly the pressure and load on thebuildings.The experiments were repeated for different urban settlements, flood intensities (two differentinitial water depths in the reservoir) and roughness layers along the slope, representative of avegetated and a non-vegetated hill. In the present study, the experimental results were describedqualitatively and compared with theoretical processes and 2D numerical results obtained usingOpenFOAM’s RAS turbulent model. Water depth, velocity and load measurements were anal-ysed for different cases and it was found that while the 2D model provided a good fit on theslope, the flows generated around the building were more complex 3D formations which lead toinaccuracies.All experiments were repeated multiple times to ensure repeatability and thus the procedurewas validated successfully providing a complete dataset that can be used for the validation ofcomputational models for extreme events.

Keywords: dam break flow, physical model, experimental data, urban flood, flash flood, extreme

events, structure interaction, sloping channel, computer model validation


131



A Study on Evacuation Safety at Inundated Stairs by usingReal-scale Hydraulic Model Experiment

Myounghwan Kim ∗† 1, Du-Han Lee 1, Ji-Sung Kim 1, Jung-Hyun Eom 2

1 Korea Institute of Civil Engineerig and Building Techno (KICT) – 283, Goyang-daero, Ilsanseo-gu,Goyang-si, Gyeonggi-do, 10223 – South Korea

2 Inha University – 100 Inha-ro, Nam-Gu Incheon, 402-751 – South Korea

In recent years, sudden and local downpours in Korea have become more frequent. Theserainfall patterns increase load on drainage system and reduce ability to exclude inland water,leading to flooding. If such rainfall patterns lead to flash floods especially in dense urban areas,sudden submergence of underground spaces by floods can be a fatal threat to life. Therefore,it is very important to secure evacuation routes in case of inundated underground spaces. Inthis study, we tried to determine evacuation safety by understanding hydraulic characteristics ofinundated stairs that could become evacuation routes in underground spaces. For this purpose,water depth and volume flow rate were measured at each point of inundated stairs, and dataobtained from results were used to evaluate evacuation safety at each step.

Keywords: urban flood, underground flooding, inundated stairs, evacuation safety, real scale ex-

periment


132



Sewer overflow in the urban model MURI

Tariq Chibane ∗† 1, Andre Paquier 1, Saadia Benmamar 2

1 Irstea centre de Lyon-Villeurbanne, UR RiverLy – 5, rue de la Doua CS70077 69626 Villeurbannecedex – France

2 Ecole Nationale Polytechnique d’Alger – 10, Avenue Hassen Badi, El Harrach, Alger – Algeria

Floods are one of the main natural hazards in the world and cause a lot of damages on urbanareas. In an urban flood, interaction between surface runoff and flow into the sewer system cantake place. The consideration of this interaction is necessary to understand the phenomenonof urban flooding. In order to investigate flows and to properly understand and describe theexchange of flows between the surface runoff and the sewage network during floods event, afacility called MURI was built at Irstea hydraulics laboratory. It represents a city area with itssewage network and will allow to carry out experiments to better understand the phenomena ofurban floods and to validate the numerical simulations. After the set-up of the facility, a seriesof preliminary experiments were carried out in order to check the facility and the calibrationof the various devices. At first, using an ultrasonic sensor (US), the topography of the secondfloor was determined in order to be able to obtain a reliable value of the water depth from themeasurement of the water level. In a second time, various simple configurations with variousflow regimes permitted to estimate the real roughness of the material (PVC) for the surfaceand the sewer network. Using Darcy-Weisbach and Manning-Strickler equations, the calibrationresults agree with process based values (size of roughness of about 0.1 mm). In the same time,the discharges are measured using flowmeters at the upstream and the downstream of the model;a slight measurement bias has been observed between flowmeters because of the air entrainmentat the downstream end. The first configuration that was studied is a 5.4 m long and 0.15 m widesingle street with a slope of 0.1% and two street inlets (the diameter of the orifice is 14mm) thatensure the connection of one cross section of the street with the sewage network. A flow of 3 L/ s was launched into the street. The weir downstream was 40 mm high, in order to control thewater depth in the street (about 81 mm above the closed street inlets) and to obtain a reliablevelocity profile for a large part of the water depth. In the sewer pipe, a flow of 0.5 L/s wasused and the pressure was such that, after the opening of the two orifices, overflow occurredfrom the pipe to the street with a discharge of about 0.32 L/s. The exchange flow dischargecan be calculated using either an orifice equation or the head loss in the two pipes connectingthe street and the sewage network. If the first method is quite fair with a classical coefficient of0.6, the second one provides a too high discharge because head losses are higher than estimated.This result can be due to the complexity of the flow particularly in the street near the inlets.The outflow from the bottom creates a blockage of the upstream flow and thus both a riseof water surface upstream and an acceleration of the flow in the middle of the street close tothe inlets. Secondary flows created by this process are propagating downstream changing thevelocity profiles as far as the downstream end. A second experiment in the same street and withthe same street inlets but with an inflow discharge of 2 L/s in the street and a downstream weirheight of 50 mm (to obtain the same water depth as for 3 L / s) was performed. Results arequite similar but as expected, the effect close to the street inlets was stronger with a measuredvertical velocity up to 0.2 m/s.

Keywords: Laboratory experiments, Urban floods, Flow exchanges, Street inlets, Sewage network...


133



Numerical study of building drag dissipation formulations inthe integral porosity shallow water model

Ilhan Ozgen ∗† 1,2, Martin Bruwier 3, Jiaheng Zhao 2, Dongfang Liang 4, PierreArchambeau 3, Benjamin Dewals 3, Kenichiro Kobayashi 5, Satoru Oishi 1,5, Reinhard

Hinkelmann 2

1 RIKEN Advanced Institute for Computational Science – Japan2 Chair of Water Resources Management and Modeling of Hydrosystems, Technische Universitat Berlin,

secr. TIB1-B14, Gustav-Meyer-Allee 25, 13355 Berlin – Germany3 HECE, UEE, University of Liege – Belgium

4 Geotechnical and Environmental Research Group, University of Cambridge – Trumpington StreetCambridge CB2 1PZ – United Kingdom

5 Research Center for Urban Safety and Security, Kobe University – Japan

The integral porosity shallow water model is a type of porous shallow water model forurban flood modeling, that defines two types of porosity, namely a volumetric porosity insidethe computational cell and a conveyance porosity at each edge. Porosity terms are determineddirectly from the underlying building geometry, hence buildings do not need to be discretizedexactly. This enables simulations with significantly reduced CPU time on meshes with cell sizeslarger than the building size. Here, the macroscopic model view leads to an additional sourceterm at the unresolved building-fluid interface, yielding a building drag dissipation source term.In literature, several formulations for this term can be found. The integral porosity shallowwater model is sensitive to the building drag dissipation, and using the drag parameters as acalibration parameter enhances the accuracy of model results. However, the ideal way to achievethis is still an open research question. In this contribution, we present a simple technique toestimate building drag dissipation that uses the conveyance porosity configuration to estimatethe projected area inside the cell, which is then used in a drag force equation. The advantageof this approach is that it is computationally inexpensive, no additional parameters need to bestored, and only a single parameter has to be calibrated. The proposed approach is comparedwith drag dissipation formulations from existing literature in a laboratory experiment thatfeatures a dam-break against an isolated obstacle. The aim of the comparison is to evaluatepresent existing building drag dissipation models with regard to accuracy and computationalcost.

Keywords: porous shallow water equations, integral porosity model, building drag, comparative

study


134



1D/2D porosity model for urban flood modeling: case of adense street networks

Pascal Finaud-Guyot ∗† 1,2, Pierre Garambois 2,3, Shangzhi Chen 3, Guilhem Dellinger 1,Abdellah Ghenaim 2, Abdelali Terfous 2

1 Ecole Nationale du Genie de l’Eau et de l’Environnement de Strasbourg (ENGEES) – France2 Laboratoire des Sciences de l’Ingenieur, de l’Informatique et de l’Imagerie (ICube) – ENGEES, Univ.

Strasbourg, INSA – 300 bd Sebastien Brant - BP 10413 - 67412 Illkirch cedex, – France3 INSA de Strasbourg – France

An increasing urbanization of floodplains has led to higher vulnerability of urban areas.Floods consequences can be severe with huge damages and human losses, especially for extremeevents. Improving prediction systems and mitigation measures has become a priority. Thereforebuilding more accurate and robust urban flood models appears as necessity and may requirea better understanding of urban floods hydrodynamics. In the field of urban flood modelingseveral approaches have been proposed using shallow water equations (SWE) either in 1D or in2D (Arrault et al., 2016; Bazin, 2013; Finaud-Guyot et al., 2011; Hervouet et al., 2000), SWEmodified with porosity (Finaud-Guyot et al., 2010; Guinot, 2012), or even 3D Navier Stokesequations (Araud, 2012). Each of these hydrodynamic models may be more or less adapteddepending on the real physical complexity of the flow. The most complex models are com-putationally expensive and require a generally unaffordable amount of data to be constrained.For instance, the flow complexity at a crossroad and downstream is at least 2D in space. Aflow recirculation generally occurs downstream of a crossroad, leading to a constriction of theeffective flow section. In view to achieve cheap and reliable simulations a new 1D/2D approachis introduced for complex hydraulic meshes (Chen, In redaction). A coupling is achieved be-tween 1D for the streets and 2D Shallow Water equations for the crossroads. A complementaryparametrization of the 1D equations with a porosity term is introduced to account for the effectof recirculation areas occurring downstream of each crossroad. This approach is tested on an alarge experimental dataset obtained on the Icube urban flood experimental rig (Finaud-Guyotet al., n.d.). It consists of numerous flood cases on a densely instrumented urban geometry. Foreach street, the porosity distribution is calibrated in order to reproduce the experimental data.However, such a porosity calibration requires the sought water depth and discharge distributionsat the crossroad scale. Therefore, some porosity functions based on empirical and hydrodynamicconsiderations have been implemented. The accuracy of those functions are assessed at differ-ent scales with two different experimental configurations: a simple 4 branches crossroad and anetwork composed of multiple 4 branches crossroads (Icube urban flood experimental rig). Thesensitivity of the modeled water levels and discharge distributions with the 1D/2D model withporosity is assessed and compared to full 2D and 3D approaches.

Keywords: 1D2D porosity model, urban flood, experiment


135



136



16:10 – 17:50

BC 6 – Computational hydrodynamics . . . . . . . . . . . . . . . . . . 138

Me 6 – Dams and reservoirs – part 2 . . . . . . . . . . . . . . . . . . . 143

Li 6 – Field measurements of sediment transport . . . . . . . . . . . . 148

Br 6 – Urban porosity models . . . . . . . . . . . . . . . . . . . . . . . . 153

137

Thursday 6 September, 16:10 – 17:50 BC 6 – Computational hydrodynamics

Implicit 2D surface flow models performance assessment:Shallow Water Equations vs. Zero-Inertia Model

Javier Fernandez-Pato ∗† 1, Mario Morales-Hernandez 1,2, Pilar Garcıa-Navarro 1

1 LIFTEC-CSIC, University of Zaragoza – Spain2 Dept. Soil and Water. EEAD-CSIC – Spain

Zero-Inertia (ZI) models are used in overland flow simulation due to their mathematicalsimplicity, compared to more complex hypothesis as Shallow Water (SW) models. The mainhypothesis in ZI models is that the flow is driven by water surface and friction gradients, neglect-ing local accelerations. On the other hand, SW models are a complete dynamical formulationthat provide more information at the cost of a higher level of complexity. In realistic problems,the usually huge number of cells required implies a large amount of computing effort and time.This is particularly true in 2D models. Hence, there is an interest in developing efficient nu-merical methods. In general terms, numerical schemes used to solve time dependent problemscan be classified in two groups, attending to the time evaluation of the unknowns: explicit andimplicit methods. Explicit schemes offer the possibility to update the solution at every cell fromthe known values but are restricted by numerical stability reasons. This can lead to very slowsimulations in case of using fine meshes. Implicit schemes avoid this restriction at the cost ofgenerating a system of as many equations as computational cells multiplied by the number ofvariables to solve. In this work, an implicit finite volume numerical scheme has been used tosolve the 2D equations in both ZI and SW models. The scheme is formulated so that bothquadrilateral and triangular meshes can be used [1,2]. A conservative linearization is done forthe flux terms [3], leading to a non-structured matrix for unstructured meshes thus requiringiterative methods for solving the system. A comparison between 2D SW and 2D ZI is donein terms of performance, efficiency and mesh requirements, in which both models benefit of animplicit temporal discretization in steady and nearly-steady situations.

Keywords: Finite volumes, implicit shcemes, shallow water equations, zero, inertia model, perfor-

mance assessment


138



Novel approaches for large-scale two-dimensional hydrodynamicmodelling of rivers

Mohamed Yossef ∗† 1, Jurjen De Jong 1, Aukje Spruyt 1, Martin Scholten 2

1 Deltares – Netherlands2 RWS-wvL – Netherlands

For decades, the decision-making process for water management in the Netherlands makesfull utilisation of state of the art models. For rivers, two-dimensional hydrodynamic modelsare considered essential for a wide range of questions. Every five years, there is a major modelrevision that includes software updates, improved physical processes, new modelling strategy,and a new calibration. 2017 marked the setup and calibration of the first river model in thesixth generation of these models. In this paper, we discuss the most recent developments intwo-dimensional hydrodynamic modelling of rivers. We give an overview of the process followedto agree on the functional design of the model and address the use of the recently developedDelft3D Flexible Mesh suite. We address, in some details: i) a mesh independent approach formodel setup; ii) the utilisation of a new calibration technique, which is automated using dataassimilation and includes spatial and discharge dependencies; and iii) the use of a novel opera-tional module to control hydraulic structures. The first river model within the 6th generation ofmodels is that of the Meuse River, where the new approaches are being successfully applied. Inconclusion: the mesh independent modelling approach offers great flexibility and facilitates thatthe same data set can be used for multiple versions of the model (e.g. different grid resolution;or different model extent). The automated calibration approach makes it possible to utilise acomprehensive calibration data set for a large-scale model in a reproducible way. The increasedcomplexity of modelling has become possible over the last decade due to the availability oflarge datasets and increased computational power. This paper is particularly relevant for bothmodellers and decision makers.

Keywords: Hydrodynamics, models, Meuse River, Netherlands, calibration, Delft3D Flexible Mesh,

data assimilation, Deltares


139



Numerical shockwave anomalies in the resolution of the shallowwater equations with bed variations

Adrian Navas-Montilla ∗† 1, Javier Murillo 1

1 University of Zaragoza (EINA) – Spain

The presence of numerical shockwave anomalies appearing in the resolution of hyperbolicsystems of conservation laws is a well-known problem in the scientific community. The mostcommon anomalies are the carbuncle and the slowly-moving shock anomaly. They have beenstudied for decades in the framework of Euler equations, but only a few authors have consideredsuch problems for the Shallow Water Equations (SWE). In this work, the SWE are consideredand the aforementioned anomalies are studied. They arise in presence of hydraulic jumps,which are transcritical shockwaves mathematically modelled as a pure discontinuity. Whensolving numerically such discontinuities, an unphysical intermediate state appears and gives riseto a spurious spike in the momentum. This is observed in the numerical solution as a spikein the discharge appearing in the cell containing the jump. The presence of the spurious spikein the discharge has been taken for granted by the scientific community and has even becomea feature of the solution. Even though it does not disturb the rest of the solution in steadycases, it produces an undesirable shedding of spurious oscillations downstream when consideringtransient events. We show how it is possible to define a coherent spike reduction technique thatreduces the magnitude of this anomaly and ensures convergence to the exact solution with meshrefinement. Concerning the carbuncle, which may also appear in presence of strong hydraulicjumps, a combination of Riemann solvers is proposed to circumvent it. Also, it will be shownhow there is still room from improvement when treating anomalies in moving hydraulic jumpsover variable topography.

Keywords: shallow water, finite volume, hydraulic jumps, shockwave anomalies


140



Vortex-Resistance Hypothesis: Large Eddy Simulation ofTurbulent Flow in Isolated Pool-Riffle Units

Hamed Dashtpeyma ∗ 1, Bruce Macvicar † 1

1 Civil and Environmental Engineering Department, University of Waterloo, Waterloo, Ontario, N2L3G1, Canada

By numerical simulations of turbulent flow in isolated pool-riffle units with various riffleheights, four different types of vortices were found and named as follows: surface rollers (SR),corner rollers (CR), ramp rollers (CR), and axial tails (AT). Surface rollers are shaped on theflow surface due to submerged hydraulic jump or any obstacles in the forced pool-riffle units.Corner rollers are shaped close to the corners near the walls at the pool head. Ramp rollers areformed at the bed of the channel on the ramp into the head of the pool. All kinds of vorticesstretch in the streamwise direction as they travel to the downstream, which they are called axialtails. The simulations showed that all four types of vortices interact with each other, combine,amplify or cancel out each other as they travel downstream. The strength of vortices and howthey interact result into different types of flow patterns. The surface rollers combine with cornerrollers to make a jet like plunging flow near the pool bed. In other cases with lower riffle heights,ramp rollers tend to push the flow up, which in turn leads to higher turbulence near the bedand higher velocity near the flow surface (skimming flow). Moreover, if both surface rollersand ramp rollers have the similar strength (e.g., vorticity) and scale, the streamwise velocityprofile has a peak around the middle of the flow, and minimum velocities near the bed andfree surface. This flow pattern was named as ”rifting flow.” Based on these findings, a newhypothesis is proposed called ‘vortex-resistance,’ which states that the turbulent structures, byincreasing the eddy viscosity and changing the pressure domain, act as an obstacle that steersthe flow. Plunging and skimming flow can thus be understood as the products of different typesof turbulent structures. These findings provide new clarifications to long-standing questionsrelated to the hydraulics of pools and riffles.

Keywords: LES, Pool, Riffle, Plunging flow, Skimming flow, Rifting Flow, CFD, Turbulent flow


141



IDDES Evaluation of Oscillating Hydraulic Jumps

Vimaldoss Jesudhas ∗† 1, Frederic Murzyn 2, Ram Balachandar 1

1 University of Windsor Canada – Canada2 Ecole Superieure des Techniques Aeronautiques et de Construction Automobile (ESTACA)– France

This paper presents the results of three-dimensional, unsteady, Improved Delayed DetachedEddy Simulations of an oscillating and a stable hydraulic jump at Froude numbers of 3.8 and 8.5,respectively. The different types of oscillations characterized in a hydraulic jump are analyzed byevaluating the instantaneous flow field. The instability caused by the flapping wall-jet type flowin an oscillating jump is distinct compared to the jump-toe fluctuations caused by the spanwisevortices in the shear layer of a stable jump. These flow features are accurately captured by thesimulations and are presented with pertinent discussions. The near-bed vortical structures inan oscillating jump are extracted and analyzed using the lambda-2 criteria.

Keywords: oscillating hydraulic jumps, jump toe oscillations, improved delayed detached eddy

simulation, air, water multiphase flow, coherent structures


142



Direct field observations of massive bedload and debris flowdepositions in open check dams

Guillaume Piton ∗† 1,2, Firmin Fontaine 1, Herve Bellot 1, Frederic Liebault 1, CoralineBel 1, Alain Recking 1, Therese Hugerot 3

1 Irstea centre de Grenoble, UR ETNA – 38041 St-Martin-d’Heres – France2 Universite Grenoble Alpes –Grenoble – France

3 Environnements, Dynamiques et Territoires de la Montagne (EDYTEM) – CNRS : UMR5204, Univ.Savoie – 73376 Le-Bourget-du-Lac cedex – France

Sediment detention basins, also called SABO dams, are key facilities in flood protectionsystems of mountain catchments, specifically in torrents prone to massive bedload transport ordebris flows. A better understanding of the processes generating sediment trapping is requiredto optimize their functioning. Two monitoring stations have been implemented in the FrenchAlps on two torrents: the Manival (Saint-Nazaire-Les-Eymes) and the Claret (Saint-Julien-Mont-Denis). Time-lapse photos show an event depositing 10,000 m3 of debris flow in a basin inless than six minutes and several events partially filling the other basin with gravel, impairingits capacity to store debris flows later. After a presentation of the catchments, this paperqualitatively analyzes the dynamics of the depositions. It highlights and stresses the consistencyand differences between bedload and debris-flow deposition. Overall, despite clear differencesof geomorphic activity, deposits tend to fill the trap basins just enough to enable the sedimenttransport continuity reestablishment through the basin. The open check dams thus play a roleonly provided that this continuity precondition is completed. These observations enhance ourcomprehension of massive sediment trapping in torrents and our capacity to better adjust trapmaintenance and design to the objective sought in each site.

Keywords: torrential barrier, steep slope stream monitoring


143



Experimental investigation of reservoir sediments

Felix Beckers ∗† 1, Stefan Haun 1, Markus Noack 1

1 University of Stuttgart, Germany – Germany

Reservoir sedimentation can reduce the lifetime of a reservoir and may have negative impactson the operation as well as on the affected downstream region. Thus, sustainable sedimentmanagement strategies are required to minimize reservoir sedimentation, to remobilize alreadydeposited material and to restore natural sediment continuity at its best. However, successfulmeasures can only be derived when detailed knowledge of the sediment characteristics and thesediment erosion stability as well as their mutual interaction exists. In this context, especiallythe description of fine sediment mixtures consisting of clay, silt and sand is a challenge dueto their cohesive erosion behavior. These sediment groups, however, often dominate reservoirsediments. Therefore, this study presents an experimental approach to analyze the composition,the characteristics and the stability of reservoir sediments by taking into account physical,chemical and biological parameters. In a first step, adjacent sediment cores are taken from thereservoir with a so called ”Frahm-Lot”. This device was previously used in marine technologyand is applied in inland waters for the first time. With the device, undisturbed sediment coreswith a diameter of 0.1 m and a length of up to 1 m can be extracted from the reservoir bed.It can be operated from a floating platform up to a maximum depth of 100 m. The extractedcores are subsequently used for experimental investigations in the laboratory. First, verticalprofiles of bulk densities are determined for all cores by using a non-destructive gamma-rayattenuation method. The physical principle is to measure the absorption of gamma radiationby a penetrated media. The attenuation of the sediment can be correlated with the attenuationof air and water resulting in the sediment bulk density. Based on corresponding bulk densityprofiles, cores get grouped and are selected for further destructive analyses. One part of thecores is used to evaluate particle size distribution (PSD), total organic carbon (TOC), cationexchange capacity (CEC), extracellular polymeric substances (EPS) and Chlorophyll-a (CHL-a) in different horizontal layers. This leads to representative vertical profiles along the cores.PSD is determined by laser diffraction, TOC by loss on ignition, CEC by exchange with bariumchloride and EPS as well as CHL-a by a photometric analysis. The second part of the cores inthe group is used to determine the erosion stability in the same horizontal layers to enable acomparison with the investigated parameters. For this purpose, an erosion flume (SETEG) anda photogrammetric method is applied to measure the erosion rates at different induced shearstresses. The critical shear stress can be calculated from the measured erosion rates to derivethe sediment stability in each layer. Finally, all results of corresponding cores can be correlatedwith each other to investigate the depth-dependent influence of the investigated parameters onthe measured sediment stability.

Keywords: Sediments, reservoirs, cohesive sediments


144



Toward an operational approach for the characterization andmodelling of fine sediments dynamics in reservoirs

Christophe Peteuil ∗† 1, Magali Jodeau 2, Matthieu De Linares 3, Eric Valette 4, DamienAlliau 1, Carole Wirz 1, Thierry Fretaud 1, Germain Antoine 2, Matthieu Secher 4

1 Compagnie Nationale du Rhone (CNR) – Direction de l’Ingenierie et des Grands Projets – 2, rueAndre Bonin - 69316 Lyon cedex 04 – France

2 Laboratoire National d’Hydraulique et d’Environnement, EDF R &D – 6 quai Watier, 78401 ChatouCedex – France

3 Artelia – Departement Eau & Environnement – 6, rue de Lorraine Echirolles cedex – France4 Centre d’Ingenierie Hydraulique CIH-EDF – 15 avenue Lac du Bourget Passerelles Savoie Technolac

73373 Bourget-du-Lac – France

Achieving a sustainable management of sediment fluxes in existing or proposed reservoirs isa challenging but essential requirement for dam operators. Such objective is of utmost impor-tance to avoid sedimentation-related consequences. Numerical modelling is of great interest tounderstand the flow and sediment dynamics in a reservoir, to simulate the long-term evolutionof sediment deposits and to evaluate the efficiency of various management strategies. This pa-per presents recent case studies, which validate the feasibility and relevancy of such technicaloption. The progresses obtained on essential stages of the numerical modelling of sedimentsdynamics in reservoirs are particularly emphasized. Concerning the distribution of deposits, apromising field method based on an optimum combination of direct samplings with acousticmeasurements and video auscultations is detailed. Feedbacks are then provided concerning aninnovative device deployed in the field for a direct measurement of the settling velocity. Issuesabout the assessment of calibration parameters are also addressed in this communication. Labexperiments performed on deposits sampled in several reservoirs provide practical guidance toevaluate the erosion parameters of sediments. Finally, several examples of sediment dynamicsmodelling in reservoirs including both cohesive and non-cohesive sediment are presented.

Keywords: reservoir sedimentation, sustainable sediment management, sediment dynamics mod-

elling, field survey, lab tests, settling velocity, erosion parameters


145



Influence of lateral embayments on suspended sedimenttransport under unsteady flow conditions

Carmelo Juez ∗† 1, Matthias Thalmann 1, Anton J. Schleiss 1, Mario Franca 1

1 Ecole Polytechnique Federale de Lausanne (EPFL), Laboratoire de Constructions Hydraulique

(LCH), Lausanne – Switzerland

Local widening in a channelized river is a common practice in restoration projects. Thelateral embayments built for this purpose in the river banks are partially filled up by fine sedi-ments creating potential for riparian habitat. However, the design of these lateral cavities maybe compromised by the fluctuations in the water discharge. Pursuing a better understanding onthe design of lateral embayments, systematic experimental investigations have been carried outwith five different fluctuating hydrograph scenarios. Water depth, sediment concentration andarea covered by the settled sediments are analyzed in each experiment. The process of sedimen-tation in the lateral embayments proofed to be very resilient to flushing. However, there areconsiderable differences in what happens during the flushing event depending on the geometricconfiguration of the embayments and the flushing hydrograph applied: (i.) A higher peak indischarge means that more sediments are resuspended and the risk of a complete flushing in-creases. (ii.) Long and short cavities retain their depositions more efficiently from resuspensionthan cavities of intermediate length. Long cavities have large dead water zones with well shel-tered depositions. Short cavities have skimming flow type, i.e. the dynamics within the cavitieswidely decoupled from the main flow, and are therefore able to retain the sediments.

Keywords: River embayments, macro, roughness lateral elements, fine sediments, unsteady flow,

hydropeaking, seasonal flows, groyne fields


146



Estimating Reservoir Sedimentation at Large Dams in India

David Froehlich ∗† 1

1 Independent Consultant – United States

Eroded sediment transported by natural streams tends to settle out when it enters the com-paratively calm water of an artificial lake (a reservoir) created by a dam to store the water.The rate of water storage loss depends on the annual sediment load carried by the streams andthe extent to which that material is retained in the reservoir. The amount of sedimentation iscontrolled by a number of factors including the area and geologic origin of the catchment, theland uses (cultivation practices, grazing, logging, construction activities, and conservation prac-tices), the amount of rainfall, the reservoir storage capacity, the duration of storage in relationto the sediment load of the stream, the particle size distribution of the suspended sediment, theplanform configuration of the reservoir, the location and size of sluices and other outlet worksat the dam, and the method and purpose of water releases through those outlets.As time passes, a reservoir continues to fill with sediment, which reduces the available storagevolume and may interfere with the operation of dam outlet works and hydropower intake struc-tures. The question is, how long will it take before the functions of the dam and its reservoirare so severely affected by sedimentation that continued operation becomes untenable?

The rate of sedimentation in a proposed or existing reservoir may be estimated in several ways.The approach followed here is based on an evaluation of sedimentation in existing reservoirsin which the accumulated deposits have been surveyed over an extended period. The data areobtained from a compendium of storage loss from siltation at 243 reservoirs in India (CWC2015). Mathematical models are developed that relate reservoir capacity loss to catchment area,reservoir surface area, the original storage volume, and the time since the first filling of the im-poundment. Models prepared for sedimentation of reservoirs found on eastward, and westwardflowing regions differ significantly. The formulations give good fits to the assembled data.

REFERENCECentral Water Commission (2015). Compendium on silting of reservoirs in India. Ministry ofWater Resources, Watershed and Reservoir Sedimentation Directorate,New Delhi, Delhi, India.

Keywords: sedimentation, reservoir, dams, India


147


Thursday 6 September, 16:10 – 17:50 Li 6 – Field measurements of sediment transport

Bedload transport in a steep alpine stream: assessment ofsediment mobility and virtual velocity using the bedload

tracking

Riccardo Rainato ∗† 1, Lorenzo Picco 1, Daniele Oss Cazzador 1, Luca Mao 2

1 Department of Land, Environment, Agriculture and Forestry, University of Padova. – Italy2 Department of Ecosystems and Environment, Pontificia Universidad Catolica de Chile. – Chile

The bedload transport is challenging to analyze in field, consequently, several assumptionsabout it were made basing on laboratory researches or on short-term field studies. During thelast decades several monitoring methods were developed to assess the bedload transport in thefluvial systems. The aim of this work is to investigate the transport of the coarse sedimentmaterial in a steep alpine stream, using the bedload tracking. The Rio Cordon is a typicalalpine channel, located in the northeast of Italy. It is characterized by a rough streambedwith a prevalent boulder-cascade and step pool morphology. Since 2011, 250 clasts equippedwith Passive Integrated Transponders (PIT) were installed in the main channel, to analyzetheir mobility along a reach 320 m long. From November 2012 to August 2015, the transportinduced by a range of hydraulic forcing between 0.44 m3 s-1 and 2.10 m3 s-1 was assessed by10 PIT-surveys. First, the mobility expressed by the tracers was analyzed, observing markeddifferences in terms of travel distance. Then, the average recovery rate achieved during thetracer inventories (Rr > 70%) permitted to define the threshold discharge for each grain sizeclass analyzed and, then, to assess the virtual velocity experienced by the tracers.

Keywords: Bedload, tracers, alpine channel


148



Evaluation of an acoustic Doppler technique for bed-loadtransport measurements in sand-bed rivers

Slaven Conevski ∗† 1,3, Axel Winterscheid 2, Nils Ruther 1, Massimo Guerrero 3, ColinRennie 4

1 Norwegian University of Science and Technology – SP Andersens vei 5, Norway;2 Federal Institute of Hydrology, 56068 Koblenz – Germany;

3 University of Bologna – Via Terracini 28/Via Lazzaretto 15/5, Bologna – Italy;4 Civil Engineering, University of Ottawa – 161 Louis Pasteur St. Colonel By building, office A-015 ON,

K1N 6N5 – Canada

The quantification of the bedload transport in fluvial environments is a notoriously diffi-cult and labor-intensive task. The temporal and spatial variability of the bed load togetherwith the instrument disturbance can induce stochastic and systematic uncertainties. These dataare usually considered as unreliable, which complicates the further elaboration of the sedimenttransport behavior. Statistically valid measurements are extremely important for the evalua-tion of the sediment transport masses, especially in large navigable or heavily exploited rivers.Recently, many studies showed that the measurements with the bottom tracking (BT) featureof the acoustic Doppler current profilers (ADCP) have emerged as a promising technique inevaluating the bed load. The use of these non-intrusive techniques could significantly reducethe uncertainty. Firstly, they do not disturb the riverbed and are easy to deploy. Secondly, verylong and frequent measurements can be easily performed. Widespread implementation of theADCP BT bedload technique would reduce the scarcity and statistical uncertainty of bed loaddata.Strong statistical correlations are reported between the ADCP BT velocity and the transportrate obtained by physical sampling or dune tracking; however, these relations are strictly site-specific and a local calibration is necessary. Previous laboratory research has demonstrated thatwith rather simple filtering and smoothing of the ADCP BT velocity (denoted as the apparentvelocity), one can obtain relatively correct spatially averaged velocity of the bed surface. Devia-tion in the results is assigned to the coupling between acoustic waves at the given instrumentalfrequency, the size distribution of mobile particles (i.e., PSD) and the riverbed morphology.The aim of this work is to develop a methodology for evaluating the bed load transport usingcommercial ADCPs without calibration with physical samples. Relatively long stationary mea-surements were performed in a sand-bed river using three different ADCPs working at 3MHz,1.2MHz and 0.6MHz. Simultaneously, bed load samples were collected with physical samplers,and the riverbed was closely observed with digital cameras mounted on the samplers. By dis-carding only the aliased values and the flow-opposite values from the apparent ADCP velocity,the velocity magnitudes and directions are significantly improved. Additionally, the transmissionloss of the signal in the active layer is evaluated and compared with the empirically estimatedthickness. The results obtained from the different ADCPs are analyzed and compared; it isdemonstrated that the local calibration of apparent velocity to estimate bedload transport rateis associated not only with the PSD and the spatial heterogeneity, but also with the penetra-tion of the signal through the active layer, and the internal signal processing of the instrument.It is demonstrated that the kinematic transport model can yield a relatively good estimate ofthe transport rate by directly using filtered apparent velocity and instrument-related calibra-tion coefficients. The ADCP data can also be used for a qualitative validation of the physicalsamples.

Keywords: bedload transport, ADCP, sandy rivers, kinematic transport model∗Speaker†Corresponding author: [email protected]

149



Improving bedload transport determination by grain-sizefraction using the Swiss plate geophone recordings at the

Erlenbach stream

Dieter Rickenmann ∗† 1, Nicolas Steeb 1, Alexandre Badoux 1

1 Swiss Federal Institute for Forest, Snow and Avalanche Research (WSL) – Switzerland

The Swiss plate geophone system is a bed load surrogate monitoring technique that hasbeen calibrated in several mountain streams to quantify bedload transport. The amplitude ofthe signal recorded by the Swiss plate geophone contains information about the grain-size distri-bution of the transported bedload. At the steep Erlenbach stream in Switzerland, direct bedloadsamples were taken with a large metal basket, and these measurements were compared with thesignal of the impact plate geophone system to derive information about bedload transport. Typ-ical total sample masses varied between about 5 and 380 kg. Wyss et al. (2016) developed theso-called amplitude histogram (AH) method to estimate the bedload flux for different grain sizeclasses at the Erlenbach.A reanalysis of the measurements was made recently to examine the performance of the AHmethod in the light of new findings regarding the calibration of the geophone system (Ricken-mann and Fritschi, 2017). It was found that the AH method produces reasonable estimates ofthe total bedload flux summed over all grain-size classes; however the estimation of the grain sizedistribution (GSD) revealed partly poor results. The reasons for this poor agreement with themeasured grain-size distribution are two-fold: (i) first, some samples contained comparativelysmall total bedload masses, thus limiting the number of grains per class that were transportedover the plates; and (ii) a reasonably strong correlation exists for example between the D-75of the detectable transported particle sizes and the impulse rate, i.e. the number of impulsesrecorded per sampling time, which was not taken into account in the original AH-method. Con-sidering these two new elements, an improved version of the AH method was developed thatresulted in a better agreement between the geophone-based, calculated GSD and the measuredGSD.

Rickenmann, D., Fritschi, B. (2017): Bedload transport measurements with Swiss impact plategeophones in two Austrian mountain streams (Fischbach and Ruetz): system calibration, grainsize estimation, and environmental signal pick-up. Earth Surf. Dynam. Discuss., doi:10.5194/esurf-2017-1.Wyss, C.R., Rickenmann, D., Fritschi, B., Turowski, J.M., Weitbrecht, V., Boes, R.M. (2016):Measuring bedload transport rates by grain-size fraction using the Swiss plate geophone signal atthe Erlenbach. Journal of Hydraulic Engineering, 142(5), 04016003, doi: 10.1061/(ASCE)HY.1943-7900.0001090.

Keywords: bed load surrogate monitoring, impact plate, geophone system, steep stream, grain size

distribution


150



Characterization of bed load discharge in flood bores and veryunsteady flows in an ephemeral channel

Eran Halfi ∗† 1, Joel Johnson 2, David Katoshevski 1, Ian Reid 3, Jonathan Laronne 1,Vishal Deshpande 1, Yael Peretz 1

1 Ben Gurion University – Beer Sheva – Israel2 The University of Texas, Austin – United States

3 Loughborough University – United Kingdom

There are many methods and equations for estimating bedload flux under steady flow con-ditions. Yet, little is known about the effect of very unsteady flows, such as flash floods andspecifically bores, on bedload flux. The unpredictable nature of the floods together with manylogistic difficulties and safety issues in monitoring explain this gap in knowledge, particularlyin field data. Global climate change may increase flash flood occurrence in many landscapes,making understanding of their effects even more crucial. Our study focuses on two typical con-ditions of flash flood bores: a) where they arrive on a dry river bed and b) where they overridea column of moving water, often the recession of a preceding flash flood.The methodology of our study is based on the demonstrated ability of the Eshtemoa gaugingstation to automatically monitor the variation of bedload flux (Reid slot samplers), along withinnovative equipment including underwater microphones and geophones for capturing the acous-tic signals of bedload sediments (1 Hz), surface water velocity by radar (SVR), video camerasfor continuous monitoring of water surface velocity and structure (by the LSPIV method), sur-face water slope (pressure sensors), and 3-D velocimetry for characterizing turbulence (40 Hz).Alerting sensors and cellular phone transmission enable onsite presence upon the arrival of abore.Two monitored flow events were sufficiently large to transport significant amounts of bedload;the larger event peaked at 0.8 bankfull, producing a bedload flux of up to 4 kg/sm, and havinga modest recurrence interval. Calibration of the acoustic indirect sensors against the directslot samplers allows determination of bedload flux at a frequency of 1 Hz. Analyses of the twoevents indicate a dramatic increase in turbulence (i.e. turbulent kinetic energy and instanta-neous vertical velocities), shear stress and bedload flux during the first two minutes of borearrival.

Keywords: Bedload, flash flood, bores, unsteady flow


151



Numerical simulation of bedload tracer transport associatedwith sand bar formation, bank erosion, and channel migration

Toshiki Iwasaki ∗† 1, Satomi Yamaguchi 1, Hiroki Yabe 1

1 Civil Engineering Research Institute for Cold Regions – Japan

An understanding of the bedload transport processes in rivers is essential to predict theriver morphology and morphodynamics, as well as the transport and fate of sediment-boundmaterials such as pollutant, organic matter etc. Direct measurements of the bedload transportprocesses are quite difficult, in particular, at field scales, so that the modeling for tracking thebedload transport phenomena would be powerful tools to understand the river morphodynamicsand substance dynamics. Passive tracer particles, which do not affect the bedload transport butare distinguishable from the bedload particles, have been widely used to monitor the bedloadtransport in natural environments. The models of the bedload tracer transport have been alsoproposed to express the bedload tracer motion, but the application of the model for complexsituation is still limited. In this study, we perform numerical simulations of the bedload tracertransport associated with the complex river morphodynamic processes. More specifically, wenumerically simulate the behavior of bedload tracers, which are supplied from the floodplaindue to the bank erosion, within the channel under the effects of the sand bar formation andchannel migration.The numerical model we used in this study consists of hydrodynamic module, morphodynamicmodule and tracer transport module. A two-dimensional unsteady shallow water flow model isused to calculate the flow field, and an equilibrium-type of bedload transport model is applied.A simple slope collapse model based on the concept of angle of repose is incorporated intothe morphodynamic model to reproduce the bank erosion. We use a flux-type bedload tracertransport model with the active layer approach to track and store the tracer concentration inthe bedload and substrate layers.The model is applied to a laboratory scale experiment. In the experimental flume (total flumewidth is 3 m and the length is 23 m), a straight channel (the width is 0.5 m and bank height is0.04 m) was set, and the tracer particles was installed in a part of floodplain. A steady waterdischarge and equilibrium bedload supply were given from the upstream end. The proposednumerical model well reproduces the morphodynamics of the river bed and channel migration aswell as the associated tracer transport behaviors seen in the experiment as described below. Theinitial straight channel becomes wide and the alternate sand bars develop within the channel.The alternate bars cause the erosion of the floodplain, resulting in the meandering channel.The bank erosion and channel migration transport the tracer particles on the floodplain into thechannel region. The tracer particles then are transported as bedload in the channel, but the mostof the tracer particles is captured by the scroll-bars developed within the channel. Further long-term computation of the tracer transport and the river morphodynamics indicates that activesand bar development and channel migration strongly slowed down the virtual advection speedof the bedload tracers because the active morphodynamic processes store the tracer particlesinto the substrate, causing very long waiting time of tracer particles.

Keywords: bedload tracers, river morphodynamics, numerical simulation, advection, dispersion


152


Thursday 6 September, 16:10 – 17:50 Br 6 – Urban porosity models

Investigation of distributed-porosity fields for urban floodmodelling using single-porosity models

Sandra Soares-Frazao ∗† 1, Fabian Franzini 1, Jeremy Linkens 1, Jean-Charles Snaps 1

1 Institute of Mechanics, Materials and Civil Engineering, Universite catholique de Louvain – Place duLevant 1 1348 Louvain-la-Neuve – Belgium

Porosity-based model rely on the assumption that an urban area can be compared to aporous medium, where the porosity is defined as the ratio between the actual area available tothe flow, i.e. not occupied by buildings, and the total area of the considered urban environment.In classical single-porosity models, the resulting value of the porosity parameter is consideredas constant and accounts essentially for the reduced water storage capacity and reduced spaceavailable for the flow. As a consequence, the source term involving the porosity parameter onlyaccounts for a local head loss at the entrance and at the exit of the urban area. Therefore, thehead losses occurring inside the urban area are accounted for using drag-type source terms. Inthe present work, we tested different definitions of the porosity parameter, showing the benefitsof accounting for areas with distributed porosity based on the actual layout of buildings andstreets. This formulation is still compatible with the basic idea of porosity-based model, i.eallowing for the use of coarse computational meshes instead of refined meshing of the urbanarea.

Keywords: Porosity models, variable porosity field, numerical simulations, shallow, water equations


153



Modelling urban floods using a finite element staggered schemewith porosity and anisotropic resistance

Daniele P. Viero ∗† 1

1 Department of Civil, Environmental and Architectural Engineering, University of Padova – ViaLoredan 20, 35131, Padova – Italy

(Special session porosity models) Artificial porosity models for urban flooding use porosityas a statistical descriptor for the presence of buildings, which are then treated as subgrid-scalefeatures. Computational efficiency makes porosity models attractive for large-scale applications.They are typically implemented in the framework of two-dimensional (2D) finite volume col-located schemes. The most effective schemes, falling under the category of Integral Porositymodels, allow accounting for a wealth of sub-grid processes, but they are known to suffer fromoversensitivity to mesh design in the case of anisotropic porosity fields. In the present exploratorystudy, a dual porosity approach is implemented into a staggered finite element numerical model.The free surface elevation is defined at grid nodes, where continuity equation is solved; fluxes areconveyed by triangular cells, which act as 2D-links between adjacent grid nodes. The presenceof building is modelled using an isotropic porosity in the continuity equation to account forthe reduced water storage, and an anisotropic conveyance porosity in the momentum equationsto compute bottom shear stress. Both porosities are defined on an element-by-element basis,thus avoiding mesh-dependency. Although suffering a number of limitations, the model showspromising results.

Keywords: Urban flooding, Artificial porosity, Anisotropic resistance, Mesh independence, Shallow

water models


154



Improvement of anisotropic porosity models with a mergingtechnique

Martin Bruwier ∗† 1, Pierre Archambeau 1, Sebastien Erpicum 1, Michel Pirotton 1,Benjamin Dewals 1

1 Hydraulics in Environmental and Civil Engineering, Research unit Urban & EnvironmentalEngineering, University of Liege (ULg) (HECE) – Belgium

Anisotropic porosity shallow-water models are used to take into account fine-scale topo-graphic information at a coarser modelling scale, through porosity parameters multiplying thevarious terms of the shallow-water equations. A storage porosity is assigned to each cell toreflect the void fraction in the cell and a conveyance porosity is used at each edge to reproducethe impact of subgrid obstacles on the flux terms.The numerical stability of explicit numerical schemes for solving the porosity shallow-waterequations is controlled by a modified Courant-Friedrichs-Lewy criterion, in which the time stepdepends on the storage porosity value. This may lead to a strong increase in the computationaltime in the presence of cells with low storage porosity value. Such a case is particularly expectedto arise for simulations on Cartesian grids for which the meshing stems directly from the choiceof the grid size.In this presentation, this problem is addressed using an original merging technique consisting inmerging cells with a storage porosity lower than a threshold value with neighbouring cells, andupdating accordingly the topology of the edges. The benefit of adding the merging techniquein anisotropic porosity models is highlighted for a simple configuration of a prismatic channelwith a constant discharge for which the normal water depth is prescribed at the downstreamboundary condition. Modifying the orientation between the computational grid and the channeldirection, the values of the water depths computed with a standard shallow-water model increasedue to the artificial changes of cross-section resulting from the discretization on a Cartesian grid.Using a porosity-model in which low porosity values are simply removed from the computationaldomain (no merging), these artificial changes can be significantly reduced at the cost of a signif-icant increase of the computational time (up to a factor 15). Including the merging technique inthe porosity model is shown to give a similar reduction of the numerical overestimation of theflow water depths while reducing the computational burn to a factor around 2.

Keywords: Porosity model, merging technique, Cartesian grid


155



Integral porosity shallow water model at district scale - Casestudy in Nice

Finn Amann ∗ 1, Ilhan Ozgen † 1,2, Morgan Abily 3, Jiaheng Zhao 1, Dongfang Liang 4,Kenichiro Kobayashi 5, Satoru Oishi 2,5, Philippe Gourbesville 3, Reinhard Hinkelmann

1

1 Chair of Water Resources Management and Modeling of Hydrosystems, Technische Universitat Berlin– Gustav-Meyer-Allee 25, 13355 Berlin – Germany

2 RIKEN Advanced Institute for Computational Science – Japan3 Innovative CiTy Lab (I-CiTy) – Universite Nice Sophia Antipolis, Universite Cote d’Azur – 1-3 bd

Maıtre Maurice Slama 06200 Nice – France4 Geotechnical and Environmental Research Group, University of Cambridge – Trumpington Street

Cambridge CB2 1PZ – United Kingdom5 Research Center for Urban Safety and Security, Kobe University – Japan

After three hours of intense rainfall, the city of Nice was flash flooded on October 3, 2015,resulting in casualties and severe damage in property. This study presents a porous shallowwater-model based numerical simulation of the flash flood event in a district of Nice, and com-pares the results with a high-resolution conventional shallow water model. This contributionaims to discuss practical aspects of applying a porous shallow water model to a real world case.The porous shallow water model is an integral porosity-type shallow water model. It uses un-structured triangular meshes. The conventional shallow water model is a distributed memoryparallelized high-performance computing code, that uses a uniform Cartesian grid. The studysite is an approximately 5 km2 spanning district of the city of Nice, France. Topography in-formation is available in a 1 m resolution and in addition, the available digital elevation modelincludes inframetric structures such as walls and small bridges. In the presentation of the casestudy, challenges of the pre-processing step of the integral porosity shallow water model areaddressed, and a way to semi-automatically generate ”good” triangular meshes using the open-source geoinformation system QGIS and the mesh generator Gmsh is presented. During thepost-processing step, the coarse resolution results are mapped back onto the high-resolutiontopography to make the results more meaningful. The agreement between the high-resolutionreference solution and the porous model results are poor. A speed up of about 10 to 15 wasobserved for the present case.

Keywords: integral porosity shallow water model, case study, Nice, flash flood, urban flooding


156



Experimental validation of transient source term inporosity-based shallow water models

Vincent Guinot ∗† 1,2, Sandra Soares-Frazao 3, Carole Delenne 1,2

1 Universite de Montpellier – 163 rue Auguste Broussonnet 34090 Montpellier – France2 Inria LEMON – Bat 5 – CC05 017 860 rue Saint-Priest 34095 Montpellier Cedex 5 – France

3 Universite catholique de Louvain – Belgium

Porosity-based shallow water models for the simulation of urban floods incorporate addi-tional energy dissipation terms compared to the usual two-dimensional shallow water equations.These terms account for head losses stemming from building drag. They are usually modelledusing turbulence-based equations of state (drag proportional to the squared velocity). However,refined numerical simulations of wave propagation in periodic urban layouts indicate that suchdrag models do not suffice to reproduce energy dissipation properly. Correct wave propagationspeeds, energy dissipation rates and flow fields are obtained by incorporating a new type ofsource term, active only under transient situations involving positive waves. This source termdoes not take the form of an equation of state. It can be modelled as an artificial increase inwater inertia. In this communication, an experimental validation of this source term model ispresented by means of new dam-break flow experiments in idealized, periodic urban layouts.The experimental results validate both the existence and the proposed formulation of this newsource term.

Keywords: Porosity models, experiments, wave propagation speed, energy dissipation


157



158

Friday 7 September, 8:45 – 10:25

Friday 7 September

8:45 – 10:25

BC 7 – Turbulent structures . . . . . . . . . . . . . . . . . . . . . . . . . 160

Me 7 – Ecological survey . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

Li 7 – Sediments: laboratory experiments . . . . . . . . . . . . . . . . . 170

Br 7 – River Experiment Center of Andong, Korea . . . . . . . . . . . 175

159

Friday 7 September, 8:45 – 10:25 BC 7 – Turbulent structures

Large and very large scale motions in rough-bed open-channelflows

Stuart Cameron ∗ 1, Vladimir Nikora † 1, Mark Stewart 1, Andrea Zampiron 1

1 University of Aberdeen – United Kingdom

This talk will highlight the key features of Open-Channel Flow (OCF, e.g., streams andrivers) directly relevant to sediment transport, hydraulic resistance, and eco-hydraulics. Par-ticular focus will be on ‘superstructures’ (or ‘very large scale motions’ up to 40-50 flow depthsin length). Long duration (2 to 4 hours) high-frequency (50 to 100HZ) PIV measurements ofrough-bed open-channel flows reveal that the pre-multiplied spectra of the streamwise velocitycomponent has a bi-modal distribution corresponding to the presence of large and very largescale motions (LSM’s and VLSM’s, respectively). The existence of VLSM’s in boundary layers,pipes and closed-channels has been acknowledged for some time, but for open-channels therehas previously been little supporting evidence. Length scales of the large and very large scalemotions exhibit different scaling properties; whereas the streamwise length of the LSM scaleswith flow depth, the VLSM streamwise length does not scale purely with flow depth and mayadditionally depend on other scales such as the viscous length, roughness height, the channelwidth or the boundary layer development length. The transverse extent of LSM was foundto increase with increasing elevation, but VLSM transverse scale is anchored around two flowdepths. The origin and nature of LSM and VLSM are still to be resolved, but differences intheir scaling may suggest the VLSM form independently rather than as a spatial alignment ofthe LSM’s. Potential implications of these recent findings for clarifying mechanisms of sedimenttransport, hydraulic resistance, and flow-biota interactions will be briefly discussed.

Keywords: Open Channel Flow, Turbulence, Hydraulic Resistance, Sediment Transport, Flow and

Biota Interactions


160



Turbulent structure inside and above shallow to deep canopies

Loıc Chagot ∗† 1, Frederic Moulin 1, Pierre Elyakime 1, Olivier Eiff 2

1 Institut de Mecanique des Fluides de Toulouse (IMFT) – France2 Institute for Hydromechanics, Karlsruhe Institute of Technology (KIT) – Germany

Extreme flood events are expected to become more intense and more frequent due to climatechange, and are also used as reference for the design of civil engineering structures. Accuratepredictions of both velocities and water levels for such events become a major challenge, espe-cially in urban zones, since hydraulic models calibrated with short return period events yieldlarge confidence intervals. Yet, to yield more accurate predictions, physical processes-basedmodels require a better description of the flow structure in shallow water conditions near theermergent/immerged transition. This is the larger objective of the present study which is partof the ANR Flowres project on the prediction the flow in floodplains during extreme flood eventswith changing land occupations. Turbulent boundary layer flows in and above urban or plantcanopies have been studied extensively for roughness elements geometry ranging from cubes(McDonald, 2000) to elongated cylinders (Nepf, 2012). Studies of very low submergence effectsare relatively scarce, in particular regarding the flow structure inside the canopy. This workbuilds on the previous studies of Florens et al. (2013) and Wallace (2016), who investigatedthe roughness sublayer, including the canopy for the case h/k = 6.7, and above the canopy forh/k = [1.5 − 3], respectively, where h is the water depth and k is the obstacle height. In thelater study, a logarithmic law was shown to persist even at values of h/k as low as 1.5.The specific objectives of the present work were to experimentally study the effects of very lowrelative submergence down to near critical submergence and emergence. The roughness’ ele-ments aspect ratio was also varied to examine the turbulent structure and its relation to thevarious canonical models such as boundary layers, mixing layers and wakes expected to existin these situations. The experiments have been performed in a 26 m long by 1.10 m wide by0.5 m deep glass-walled open-channel covered with prismatic roughness elements. Two kinds ofrough-beds were investigated for canopies ranging from the ”urban” type (cubes of 4x4×4 cm3)to the ”vegetation” type (elongated prisms of 12 ×2×2 cm3). The planar density λp = Ar/At

with Ar the planar area of one prismatic element and At the total area occupied by one pattern)was kept constant (λp = 0.2) to isolate the effect of the canopy depth. For all rough beds,different values of relative submergence were explored ranging from 0.5 to 4.0. The flow wasinvestigated using Particle Image Velocimetry (PIV) in 9 or 5 parallel vertical planes uniformlydistributed along one periodic pattern. To measure the velocity within the canopy, transparentBK7 glass roughness elements and a telecentric lens were used. The double-averaging method-ology proposed by Nikora et al. (2007) was employed to estimate vertical profiles of pertinentturbulent flow quantities along the whole depth of the flow with 10 000 decorrelated velocityfields for each measured plane.In the scope of this conference, we will focus on the evolution of double-averaged vertical profileswith the submergence for three kinds of canopies. We show how highly converged (both in spaceand time) profiles of double-averaged longitudinal velocity and total shear stress can be used tocalculate the vertical distribution of drag in the canopy. With this methodology, values of thedrag coefficient Cd can be calculated, and are found to be always close to unity, even in theupper part of the canopy.

Keywords: Turbulence, canopy flow, river flow, shallow flow, rough bed, PIV


161



Turbulence structures of nonuniform rough open channel flow

Priscilla Williams 1, Vesselina Roussinova ∗† 1, Ram Balachandar 1

1 University of Windsor – 401 Sunset Ave Windsor, ON – Canada

This paper focuses on the turbulence structure in a non-uniform, gradually varied, sub-critical open channel flow (OCF) on a rough bed. The flow field is analysed under accelerating,near-uniform and decelerating conditions. Information for the flow and turbulence parameterswas obtained at multiple sections and planes using two different techniques: two-componentlaser Doppler velocimetry (LDV) and particle image velocimetry (PIV). Different outer regionvelocity scaling methods were explored for evaluation of the local friction velocity. Analysis ofthe mean velocity profiles showed that the overlap layer exists for all flow cases. The outer layerof the decelerated velocity profile was strongly affected by the pressure gradient, where a largewake was noted. Due to the prevailing nature of the experimental setup it was found that thetime-averaged flow quantities do not attained equilibrium conditions and the flow is spatiallyheterogeneous. The roughness generally increases the friction velocity and its effect was strongerthan the effect of the pressure gradient. It was found that for the decelerated flow section overa rough bed, the mean flow and turbulence intensities were affected throughout the flow depth.The flow features presented in this study can be used to develop a model for simulating flowover a block ramp. The effect of the non-uniformity and roughness on turbulence intensities andReynolds shear stresses was further investigated.

Keywords: Scaling laws, Turbulence, Roughness, Nonuniform flow, LDV, PIV


162



Coherent Flow Structures in a Shallow Mixing LayerDeveloping over 2-D Dunes

Gokhan Kirkil ∗† 1

1 Kadir Has University – Turkey

A high resolution Detached Eddy Simulation (DES) is used to characterize the evolutionof a shallow mixing layer developing between two parallel streams in a long open channel overtwo-dimensional (2D) dunes. The study discusses the vertical non-uniformity in the mixing layerand provides a quantitative characterization of the growth of the large-scale quasi 2D coherentstructures with the distance from the splitter plate. The presence of large-scale roughnesselements in the form of an array of two-dimensional dunes with a maximum height of 0.25D(D is the channel depth) induces a very rapid and larger shift of the centerline of the mixinglayer due to the increased influence of the bottom roughness. Results show that in streamwisesections situated after 100D (D is the channel depth) from the splitter plate, the width of themixing layer close to the free surface stays constant. The tilting of the mixing layer interfacetoward the low speed stream is observed as the free surface is approached in all vertical sections.

Keywords: shallow flows, mixing layers, detached eddy simulation, river confluence, dunes


163



Flow structure in compound open-channel flows in the presenceof transverse currents

Sebastien Proust ∗† 1, Vladimir Nikora 2

1 Irstea centre de Lyon-Villeurbanne – 5 rue de la Doua, CS 20244, 69625 Villeurbanne cedex – France2 University of Aberdeen – King’s College, Aberdeen, AB24 3FX – United Kingdom

The structure of free-surface flows is experimentally investigated in an 18 m long and 3 mwide laboratory flume with a compound cross-section consisting of a central main channel (MC)and two adjacent rough floodplains (FPs). The study focuses on the effects of transverse currentson: (i) mixing layers and quasi-two-dimensional Kelvin-Helmholtz type coherent structures thatform at the interfaces between the MC and the two FPs; (ii) secondary current cells developingacross the channel; and (iii) large and very-large-scale motions that were recently observed byCameron et al. (2017) in non-compound rough-bed open channel flows. The study is based onone-point and two-point Acoustic Doppler Velocimetry measurements. The experiments startedwith uniform flow conditions in absence of the depth-averaged and time-averaged transversecurrents, with a constant flow depth in the longitudinal direction and with constant dischargesin each FP (8 L/s) and in the MC (98 L/s). Streamwise non-uniform flows are then generated byimposing an imbalance in the discharge distribution between MC and FPs at the flume entrance,keeping the total flow rate (Q = 114 L/s) the same as for the uniform flow setup. Five unbalancedinflow conditions have been tested, with a FP inflow of 0, 4, 12, 16 and 20 L/s at each FP. Thenon-uniform flows are associated with longitudinal changes in the flow depth and with transversecurrents. These currents represent a spanwise depth-averaged and time-averaged flow from MCto FP or vice versa, quantified by the depth-averaged transverse velocity Uyd. It is shown thateven small transverse currents can be very effective in flow modification, as they can significantlydisplace the mixing layer, shear-layer turbulence, and coherent structures towards MC or FPdepending on the currents direction. They can also alter the cross-sectional distribution andstrength of the secondary currents. The co-existence and interactions of quasi-two-dimensionalcoherent structures, very-large-scale motions, and secondary currents at different flow conditionsare also part of this study. Cameron, S. M., V. I. Nikora and M. T. Stewart (2017). ”Very-large-scale motions in rough-bed open-channel flow.” Journal of Fluid Mechanics 814: 416-429.

Keywords: mixing layer, coherent structures, Kelvin Helmholtz instability, secondary currents, very

large scale motions, transverse currents


164


Friday 7 September, 8:45 – 10:25 Me 7 – Ecological survey

Quantification of the morphodynamics and ecologicalfunctionality of a Mediterranean river

Margot Chapuis ∗† 1, Amine Ait Elabas 2, Katia Souriguere 3, Franck Compagnon 3,Vincent Mayen 4, Benoıt Terrier 4

1 Laboratoire Etude Structures, Processus d’Adaptation et Changements de l’Espace (ESPACE) –CNRS, Univ. Nice Sophia Antipolis, Univ. Cote dAzur – 98 Bd Edouard Herriot 06204 Nice cedex 3 –

France2 Universite Lumiere - Lyon 2 – France

3 Syndicat Mixte pour les Inondations, l’Amenagement et la Gestion de l’Eau (SMIAGE) – France4 Agence de l’Eau Rhone Mediterranee et Corse (AERMC) – France

The Var River (South-East France) was extensively modified (channelization, dams...) onthe 21th century and is currently undergoing an ambitious restoration project to restore its‘natural’ active braiding pattern on the downstream reach of the river.As part of the feedback evaluation of the project, this study aims at: (1) quantifying themorphological evolution of the bed that is recovering from sediment discontinuity; (2) identifyingand/or developing hydromorphological and ecological indicators which quantify improvement inthe river system from hydrosedimentary and ecological points of view.We used LiDAR and orthophoto datasets and performed analyses for unchannelized braidingrivers (Liebault et al., 2013; Lallias-Tacon, 2015). Active width (Wrestored = 242 ± 19 m vs.values ranging from 103 ± 53 to 163 ± 53 m for ‘unrestored’ reaches) and normalized bed reliefindex values (BRIrestored = 0.003 ± 0.001 vs. 0.003 ± 0.003 to 0.007 ± 0,004 for ‘unrestored’reaches) indicate a combination of low roughness and wide active width. Thus the ‘restored’reach shows a different set of indices compared to nearby ‘unrestored’ reaches, suggesting thesetools are promising in discriminating ‘restored’ vs. ‘unrestored’ reaches. Adapting existingmethods from ‘natural’ to ‘channelized’ braiding rivers widened the potential application of thetools developed by Lallias-Tacon (2015) to modified braiding river systems.

Keywords: Morphodynamics, functionality of the river system, hydromorphological and ecological

indicators, river restoration, braiding river, sediment continuity, LiDAR


165



Geomorphic identification of physical habitat features in alarge, altered river system

Lucie Guertault ∗† 1, Garey Fox 1, Shannon Brewer 2

1 Department of Biological and Agricultural Engineering, North Carolina State University – Raleigh,NC – United States

2 U.S. Geological Survey, Oklahoma Cooperative Fish and Wildlife Research Unit, Oklahoma StateUniversity – Stillwater, OK – United States

Biological patterns in streams are determined by interactions between watershed hydrologyand geomorphology, and manifest across a wide range of space and time scales (Frissell et al.,1986; Maddock, 1999). Altered flow regimes in streams can significantly affect ecosystems anddisturb ecological processes, leading to species loss and extinction. Many river managementprojects use stream classification and habitat assessment approaches to design practical solu-tions to reverse or mitigate adverse effects of flow regime alteration on stream systems.The Canadian River is a 1450-km long, wide, shallow stream, dominated by sand and mud sub-strates flowing in the Southern Great Plains of the United States. Impoundments and increasedgroundwater pumping altered flow regimes, stream connectivity and physiochemical patterns inthe Canadian River. Stream alteration led to the rapid decline of pelagic-broadcast spawningfish species emblematic of the Great Plains, that require substantial lengths of free flowing riverto complete ontogeny (Worthington et al., In press).The objective of this study was to develop a methodology to provide a primary identificationof physical habitats in an 80-km long segment of the Canadian River in central Oklahoma.The methodology relied on basic geomorphic variables describing the stream and its floodplainthat were derived from aerial imagery and Lidar data using Geographic Information Systems.Geostatistical tests were implemented to delineate habitat units. This approach based on highresolution data and did not require in-site inspection provided a relatively refined habitat de-lineation, consistent with visual observations. Future efforts will focus on validation via fieldsurveys and coupling with hydro-sedimentary modeling to provide a tool for environmental flowdecisions.

Keywords: altered river, physical habitat, geomorphology


166



Dynamic characterization of meandering channels planform

Lucas Dominguez ∗ 1, Ronald Gutierrez 2, Yoch Ponte 3, Jorge Abad † 3

1 Department of Engineering and Basic Sciences, University of Litoral. – Argentina2 Pontifical Catholic University of Peru (PUCP) – Peru

3 Water Research Center (CITA UTEC) – Peru

Meandering rivers tend to evolve along the floodplain at different migration rates during itsevolution. These rivers tend to reach a dynamic equilibrium condition that provides dominantwavelengths, amplitudes, and other planform characteristics, those properties depend on flowand sediment discharge, geologic conditions of the valley, and other variables such as soil prop-erties, vegetation among others. These physiographic features are achieved through erosion ofmargins in the concave curves and deposition of solid material in the convex areas, processes thatlead to the development of lateral (and longitudinal) migration of the river course describing asort of swept across the floodplain producing oxbow lakes at certain temporal and spatial fre-quencies (again based on the dynamic equilibrium concept, a range of frequencies are expectedfor each river). An important range of hydraulic engineering problems and scientific unknownsrequire an appropriate description of these morphological processes. Currently, remote sensingtechniques (satellite images of high resolution) provides an economical means to address theproblem in a first level of approximation, and move towards the quantification of geometricvariables that characterize the type of meandering channel. Despite the large number of stud-ies examining the geomorphological variables of meandering channels, most of them are basedon static classification and characterization of meandering rivers. This presentation outlines adynamic classification and characterization of meandering rivers where temporal variability isshown to be important to understand the behavior of these channels. We have developed aMATLAB-based toolbox to perform the characterization of several meandering rivers aroundthe world, especially in the Amazon basin. We have used Wavelet analysis, filtering techniquesand other mathematical tools to describe the equilibrium conditions of meandering rivers andtheir interaction with the geology.

Keywords: computation toolbox, meandering channels, geomorphology, migration rates


167



Predicting floodplain inundation and vegetation dynamics inarid wetlands

Steven Sandi∗ 1, Patricia Saco 1, George Kuczera 1, Li Wen 2, Neil Saintilan 3, JoseRodriguez † 1

1 University of Newcastle, Newcastle, NSW – Australia2 NSW Office of Environment and Heritage, Sydney – Australia

3 Macquarie University, Sydney, NSW – Australia

The Macquarie Marshes is a freshwater wetland system located in semiarid Australia. Theecological importance of this site has been recognized under the Ramsar convention. Plant as-sociations in the marshes has shown a complex dynamic where some wetland vegetation patcheshave transitioned to terrestrial vegetation during severe drought, but also quickly responded toincreased inflows due to record and near record rainfall accompanied by water releases from anupstream reservoir. Management decisions regarding the environmental flows require the use ofpredictive tools in order to assess the response of the vegetation. We have developed a vegeta-tion response model that couples hydrodynamic modelling of the northern Macquarie Marsheswith watering requirements of different plant associations and vegetation succession rules. Themodel simulates floods in the wetland during a series of years, after which patches of vegetationare analysed according to water depth, percent exceedance time and frequencies of inundation.During the simulated period, the patch can have adequate watering conditions, or it can havecritical conditions that would lead to a succession to another type of vegetation. The predictedvegetation is reintroduced in the model, providing feedbacks for the next simulation period. Inthis contribution, we implemented the model to simulate changes of wetland understory duringthe period 1991 to 2014.

Keywords: Macquarie Marshes, wetland dynamics, freshwater wetlands


168



Impacts of gravel-bed rivers transformation on fluvialecosystems and human society: examples from the Czech flysch

Carpathians

Vaclav Skarpich ∗† 1, Miroslav Kubın 2, Tomas Galia 1, Stanislav Ruman 1, JanHradecky 1

1 University of Ostrava (Ostrava university) – Dvorakova 7, Ostrava, 701 03 – Czech Republic2 Protected Landscape Area Administration Beskydy – Nadraznı 36, 756 61 Roznov pod Radhostem –

Czech Republic

In the last centuries, fluvial systems (especially gravel-bed rivers) in developed countrieshave undergone rapid changes in channel morphology and geomorphic pattern. The most seri-ous problems include channel transformation related to progressive channel narrowing, incisionor bed sediment coarsening. The main reasons for these transformations were connected tothe human interventions, which affected water and sediment fluxes in the basins. This papersummarizes contemporary research activities focused on these negative effects of channel trans-formations in the Czech flysch Carpathian rivers.A complex analysis of both the contemporary and the historic development of the geomorphicregime transformation were realized in the river channels draining Czech part of flysch Carpathi-ans, namely the Ostravice, Olse and Moravka Rivers. The main reasons for observed channeltransformations were connected with ‘hungry water’ effect. This was triggered by direct humaninterventions on hydrological regime as well as sediment flux by damming (e.g., valley dams,check dams, weirs), channel regulations (e.g., bank stabilisations), trans-basin diversion of wateror land cover changes of the mountainous part of the basins.As the result of channel transformations, progressive changes in fluvial ecosystem and other ef-fects on human society were observed. The initial phytosociological survey demonstrates a higherbiodiversity in the floodplain along the preserved anabranching river channel in the MoravkaRiver basin. In contrast, the floodplain along the deeply incised channel indicates lower biodi-versity values. Our observations of aquatic communities demonstrated that the channel transfor-mation connected with incision and coarsening of bed sediments negatively affected fish or brooklamprey populations in the Czech flysch Carpathian rivers. For example, habitat of Lampetraplaneri should be comprised of relatively fine bed sediments. Required sand and fine gravel aremissing or occur sporadically due to the effect of ‘hungry water’ in the transformed gravel bedchannels. Furthermore, the presence of relatively coarse bed material and high water depthsin incised channels degraded living habitats for locally common fish species (Cottus gobio andSalmo trutta).Regulation, damming and incision of channels caused changes of hydrological regime linked withgradual drying of floodplain. The analysis of floodplain groundwater fluctuations shows a de-creasing trend in the annual maximum groundwater level caused by valley dam in the MoravkaRiver basin. Additionally, a large set of hydraulic structures, bridges or weirs were affectedby undercutting and progressive destruction in the Ostravice, Olse and Moravka River basins,which is assigned to increased transport capacity of regulated channels together with decreasedsediment supply from mountainous parts of the basins.

Keywords: channel transformation, incision, ecosystem changes, Czech flysch Carpathian rivers


169


Friday 7 September, 8:45 – 10:25 Li 7 – Sediments: laboratory experiments

Erosion of fine sediments from a rough bed

Michele Trevisson ∗ 1, Olivier Eiff† 1

1 KIT-Institute for Hydromechanics (IfH) – Otto-Ammann-Platz 1, 76131 Karlsruhe – Germany

Gravel beds in river systems represent important aquatic habitats, which may be endangeredby the introduction of large amounts of fine sediments. In order to better understand theinteraction between fine sediments and coarse immobile beds in sediment supply-limited systems,a series of flume experiments was conducted. The main goal was to determine under whatconditions erosion stops. The experiments were performed over a bed of regularly arrangedspheres. Plastic particles were taken as sediment and the erosion was investigated under uniformflow conditions for variable bed shear stress conditions just above critical conditions. The systemwas observed to behave in two different ways: with higher bed shear stress fine sediments werecompletely washed out, whilst with lower stress the sediment bed reached a stable level justabove the equator of the spheres.

Keywords: sediment transport, shear stress partitioning, rough beds


170



Impact of bed surface arrangement on bedload rate:comparisons between loose, armored and water-worked beds.

Emeline Perret ∗† 1, Benoıt Camenen 1, Celine Berni 1

1 Irstea centre de Lyon-Villeurbanne, UR RiverLy – 5 rue de la Doua, 69100 Villeurbanne – France

Existing formulas for predicting bedload rate may be not adapted for mountain rivers withpoorly sorted sediments, partly because they were often established using laboratory data withconditions far from those found in such rivers. Natural bed arrangement is particularly difficultto reproduce in flumes, although recent studies highlighted its importance on bedload dynamics.This study aims to quantify bed arrangement impact on bedload rate using original laboratorytests and to improve existing bedload formulas. Three types of bed composed with the samematerial but having different bed arrangements were studied: loose beds were installed manuallyin the flume and the others, packed and water-worked beds, were created using water power.Packed beds were assimilated to flat beds composed of a static armor layer whereas water-workedbeds exhibited stronger bed organization, including large-scale bed forms. Laser-scanner surveyswere used to characterize differences in bed morphology. Similar unsteady hydraulic conditionswere applied over these beds. Results showed that bedload dynamics varies significantly depend-ing on the initial arrangement. Compared to loose bed, bedload was enhanced over water-workedbed and reduced over packed bed. Bed surface indicators are thus important parameters to takeinto account when predicting gravel transport.

Keywords: sediment transport, water, worked bed, laboratory experiments, bed arrangement


171



On experimental censorship of bed load particle hops

Francesco Ballio ∗ 1, Siobhan Fathel 2, David Furbish 2, Alessio Radice † 1

1 Politecnico di Milano – Italy2 Vanderbilt University – United States

Bed-load sediment motion can be analyzed from a Eulerian viewpoint (referred to the prop-erties of the process at some control locations) or taking a Lagrangian approach (followingindividual particles as they move). Key quantities under consideration in the latter case arethe characteristics (length, duration and mean velocity) of particle motions from entrainment todisentrainment, frequently named as particle hops. Parameterizing the particle hop propertiesas functions of the hydro-dynamic flow has been object of extensive investigation during the lastdecades.Experimental measurement of particle motions is unavoidably related with a field of view, thatcan be represented by a river reach under investigation (for example, in field studies on transportof tracer pebbles) or by an area of observation within a laboratory flume. Even though the twokinds of experimentation have very different size, they share similar shortcomings in relation tothe possibility to perform Lagrangian measurements. Let one focus on laboratory studies, thatare more numerous in the scientific literature. Potentialities and affordability of video imagingtechniques has made them very popular for the analysis of sediment transport, making largedata sets available for physical interpretation of the process. However, a Lagrangian observa-tion would be ideally required to be totally independent of a field of view. By contrast, manyincomplete hops are observed when particles cross the boundaries of the focus area used duringthe experiments. Measured probability distributions and statistical moments of the hop prop-erties can be thus biased by the occurrence of incomplete hops. Moreover, the effect of a finitearea of observation involves censorship of all hop lengths (even the shortest in a population)and not only truncation of hops longer than an area of observation. This is due to the factthat particle entrainment events can occur close to the boundaries of the measuring window.A truncation/censorship in space, due to the extent of an area of observation, has a temporalcounterpart in the duration of an experiment. Cross-effects are also expected assuming a rea-sonable correlation between hop length and duration.The paper discusses the expected effects of hop censorship from a theoretical perspective. Then,experimental censorship is demonstrated with reference to data measured in recent experimentsfrom the two research groups contributing to this work. A bias to experimental data may beavoided by appropriate experimental strategies or finding post-processing means to correct thestatistics of hop properties by removing the effect of experimental censorship. Removing cen-sorship of particle hops can significantly change the values obtained for statistical moments ofthe key quantities.

Keywords: Bed load sediment transport, Lagrangian approach, particle trajectory


172



Propagation of sediment fronts in a laboratory flume

Alessio Radice ∗† 1, Stefania Unigarro 1

1 Politecnico di Milano – Italy

Flood events in anthropic mountain areas often involve the transport of large sediment vol-umes, generally produced by slope erosion or landslides. The consequent morphologic evolutionof the river beds is of primary importance, because rapid flood events can induce significantaggradation/degradation of the bed. Sediment deposition increases the river bed level and, con-sequently, the maximum water levels, possibly causing overtopping; on the other hand, erosionnear structures can make them unstable.In this context, a key issue is the downstream migration of sediment, for which a relatively scarceknowledge is available despite some experiments exist on propagation of sediment fronts. There-fore, in this work we performed an experimental study to observe the hydro-morphologic responseof a laboratory flume subject to bed-load sediment transport and non-equilibrium upstream sedi-ment feeding. Experimental control parameters involve the bed slope, water discharge, sedimentcharacteristics, upstream sediment feeding rate. The paper presents a preliminary series of runswith uniform lightweight sediment where both the hydro-dynamic and the sediment feeding rateswere kept constant in time, the purpose of follow-up investigation being to extend the analysisto situations with unsteady boundary conditions. The physical modelling was performed in atilting flume located in the Mountain Hydraulics Laboratory of the Politecnico di Milano. Theflow discharge is measured by an electro-magnetic flowmeter. The sediment feeding is knownfrom preliminary calibration of a vibrating hopper and is also continuously measured during theexperiment. The temporal evolutions of the longitudinal profile of the stream bed and of thewater surface are measured by imaging methods. At the end of a run, an integral check of thesediment mass balance of sediment (fed-deposited-discharged) is used as a verification of theexperimental procedure. Main experimental results involve (i) the general shape of the river bedduring the process, with a separation of morphologic processes taking place at different scalesand (ii) a characterization of the velocity of propagation of aggrading and degrading sedimentfronts.The goal of the study is to provide insight on propagation of sediment fronts. However, the simi-larity between our experiments and typical numerical simulations of river morphologic change isalso evident. Hydro-morphologic river modelling typically involves the one-dimensional, shallowwater equations coupled with the Exner equation for sediment continuity and a closure relationfor evaluation of the sediment transport capacity. A morphologic model rarely involves theentire river length; most frequently, only a reach under specific analysis is considered and a sed-iment supply is input at the upstream boundary to mimic the interface between the computedriver reach and the remaining part of the catchments. The supplied material then migratesdownstream. Therefore, the experimental conditions used in this study are relevant benchmarksituations for numerical modelling of river hydro-morphologic processes.

Keywords: River morphology, sediment supply, sediment front, migration


173



Experimental study of riverbank protection withbio-engineering techniques

Sara Posi 1, Lucas Montabonnet 2, Alain Recking ∗† 2,3, Andre Evette 3, Herve Bellot 2,Frederic Ousset 2, Xavier Ravanat 2, Guillaume Piton 2,3, Luca Solari 1

1 University of Florence, Dept Civil and Environmental Engineering (DICEA - UNIFI) – via S. Marta,3 50139 Firenze – Italy

2 Irstea centre de Grenoble, UR ETNA – 2 rue de la Papeterie, 38402 St-Martin-d’Heres –, France3 Universite Grenoble Alpes – 38041 Grenoble – France

River management implies in many situation to control the river bank stability. For in-stance the retreat of river banks can be a real problem when human activities are present invery dynamics river systems. This is particularly the case in mountainous environments wheresoil occupation pressure is high and where rivers are very dynamics.Civil engineering techniques, such as concrete or rip-rap protection, have been used during thelast decades. Whereas these techniques proved to be resistant to the flow shear stress in manysituations, these structures are often oversized (especially in mountainous streams), and reduceconsiderably the ecological values of the bank protected: lower plant species diversity, increasingcolonization of invasive species and limitation of wildlife habitats.However, alternative techniques exist, and more particularly bio-engineering techniques. Thesetechniques are not new (they were already used during the nineteen century for mountain streamsrestoration), and a renewed interest could be observed during the last decade. However the de-sign of such bank protection is still largely based an expert evaluation of each situation, and westill crudely lack a real state of the art, based on mechanistic consideration of forces exerted bythe river.We present the results of preliminary flume experiments aiming to study the resistance of riverbank protections using different bio-engineering techniques. The final applied objectives will beto propose a framework for a good use of each technique, accounting for the river morphodynam-ics context. This work is a collaboration between Irstea and the French Agency for Biodiversity(AFB).

Keywords: Bank protection, bedload, vegetation, bio, engineering


174


Friday 7 September, 8:45 – 10:25 Br 7 – River Experiment Center of Andong, Korea

Flow patterns over vegetation patches in the natural channel

Yonguk Ryu 1, Joongu Kang 2, Un Ji ∗† 2, Sang Hwa Jung 2, Chang-Lae Jang 3, EllisPenning 4

1 Pukyong National University – South Korea2 Korea Institute of Civil Engineering and Building Technology – South Korea

3 Korea National University of Transportation – South Korea4 Deltares – Netherlands

Vegetation in the fields of hydraulic engineering is usually parameterized as a factor con-tributing to hydraulic roughness. In general, hydraulic roughness is considered one of the mostuncertain aspects of river modelling. Due to the ecological features of vegetation, furthermore,the roughness of vegetation does not only depend on the species, but also on the density, seasonalvariability, patchiness, undergrowth, stage and so on. This study experimentally investigatedthe effects of high and low densities of vegetation patches on the flow characteristics in a large-scale outdoor experimental channel with rooted willows. Stream-scale experiments on vegetatedflows were carried out for various hydraulic conditions, resulting in emergent, partially sub-merged, and fully submerged conditions of vegetation. Vegetation patches were arranged byalternative bar formation and the flows in vegetated and non-vegetated sections were compared.Three-dimensional flow structure was measured by ADV (acoustic Doppler velocimetry). Verti-cal, cross-sectional, and longitudinal velocity distributions were analyzed for different hydraulicconditions at various points. Flow velocities through the sparse patch were similar to those ofnon-vegetation area for low flow condition of emergent vegetation. Dense and submerged vege-tation produced more complicated and non-uniform flows over the cross-sections of vegetationpatches.

Keywords: Vegetation, natural channel, velocity measurements


175



New methods for predicting and measuring dispersion in rivers

Jonathan Nelson ∗† 1, Richard Mcdonald 1, Carl Legleiter 1, Paul Kinzel 1, TravisTerrell-Ramos 1, Yutaka Higashi 2, Il Won Seo 3

1 United States Geological Survey – 4620 Technology Drive, Golden, CO 80403 – United States2 Kyoto University – Yoshidahonmachi, Sakyo Ward, Kyoto 606-8501 – Japan

3 Seoul National University – 1 Gwanak-ro, Gwanak-gu, Seoul 151-742 – South Korea

Dispersion in rivers is a critically important part of many important physical and biologicalproblems, including predicting temperature patterns, tracking pollutants, and estimating driftof nutrients and larval fish in rivers. In the past, this problem has been treated using relativelysimple flow models coupled to concentration computations that employ empirical dispersion co-efficients to represent the effect of higher-order fluid mechanical effects, such as dispersion bysecondary flows, turbulence, and storage zones. Because of the need for a better physical rep-resentation of this problem, our group has developed a general purpose Lagrangian dispersionmodel that can be used with a wide spectrum of flow models that capture flow physics at differ-ing levels of accuracy. The model is based on a parallelized code that calculates the advectionof particles using the flow solution plus a simple random walk algorithm based on the local tur-bulent diffusivity from the flow model. This allows examination of the specific physical effectsrepresent by different models. For example, if we use a completely two-dimensional flow solu-tion for one dispersion calculation, and a three-dimensional calculation in another, the impactsof vertical shears and secondary flows can be examined. Similarly, using a three-dimensionalcalculation with different turbulence closures (e.g., isotropic vs anisotropic) the effects on dis-persion predictions can be seen by comparison of the two results and the better approach canbe judged by comparison to field data. Because the Lagrangian particle-tracking approach isperfectly parallel, as there is no interaction between advected particles, the approach is com-putationally efficient and can incorporate millions of particles, as required for results with highspatial resolution. To test the approach, we collected data on dispersion from several rivers withconventional techniques using Rhodamine dye injections and sondes for measuring concentra-tion. Comparison of the sonde measurements with the Lagrangian modeling approach showsthat the model does a good job of predicting concentrations provided that the spatial resolutionof the model is sufficient to capture river bathymetry and bank irregularities, which both playan important role in the bulk dispersion. However, the comparison is not a very complete test,as one of the shortcomings of using concentration measurements at single points is that thedetails of spatial concentration patterns are not well resolved, so comparisons can only be doneat the few spatial points where sondes are located. To deal with this issue, we explored the useof hyperspectral and conventional imagery for quantitative predictions of spatially distributeddye concentration at two sites, first using a drone on a relatively simple experimental channel atthe Korea Institute for Civil Engineering and Construction Technology (KICT) Andong RiverExperiment Center and subsequently using manned aircraft on the Kootenai River, a large me-andering river in northern Idaho. In both cases, the optical techniques were very successful.For the hyperspectral approach, simple band ratios using the Rhodamine emission wavelengthgave extremely good correlations, with r-squared values typical greater than 0.99. In addition,the low concentration or detectability levels on the hyperspectral were actually better than thesondes, with minimum levels of detectability well below 1 part per billion. Comparing the spa-tially distributed concentration results with model prediction still shows good agreement and(using different flow models) helps to explain the role of various physical approaches in produc-ing dispersion. Together, the new measurement technology strongly complements the modeling


176



approach, in that both allow unprecedented examination of spatial distributions of concentra-tion and a more complete view of the important physical processes acting to produce dispersionin rivers.

Keywords: River dispersion, mixing, hyperspectral, concentration, lagrangian

177


Experimental study on the performance analysis of river leveeusing new substance for improving earth surface resistance

Dongwoo Ko ∗ 1, Joongu Kang † 1, Sungjoong Kim 1, Yonguk Ryu 2

1 Korea Institute of Civil Engineering and Building Technology – South Korea2 Pukyong National University – South Korea

The reasons why levee breaches during floods are largely due to overtopping, seepage, andstructurally induced piping. According to an analysis of domestic and overseas reported casesof levee breaches, overtopping was found to be the cause for approximately 40% of all cases ofbreach. Despite such efforts of previous research to establish disaster prevention plans associatedwith levee breaches, to enhance our understanding of the processes and reasons, further researchregarding the prediction of levee breaches must be undertaken by accumulating test data underseveral different conditions and further verification of the data using numerical models mustalso be undertaken. In this study, development of technologies regarding a new environmentallyfriendly bio-polymer capable of protecting levees from erosion is being undertaken. Breachmechanisms was assessed using an image measurement system that collected data regarding thebreach progress of the levee, close-up views of the breaching surface, and the formation of thefinal breaching cross-sections. Further, levee slopes were covered with a bio-soil mixed with anew substance for the purpose of analyzing the stability and the time delay effect.

Keywords: Levee breach, Overtopping, New substance


178



Estimation of critical uncertainty sources in dischargemeasurements using controlled experimental conditions

Dongsu Kim ∗ 1, Aurelien Despax 2,3, Marian Muste † 4, Jerome Le Coz 3

1 Dankook university – South Korea2 Division Technique Generale EDF – Grenoble – France

3 Irstea centre de Lyon-Villeurbanne, UR RiverLy – France4 IIHR-Hydroscience & Engineering, The University of Iowa – United States

Providing experimental results along with associated uncertainties is essential not only forensuring confidence in the quality of the final results but also for guiding improved instrumentdesign and the protocols for measurement acquisition. Moreover, if the uncertainty analysis isconducted in a controlled manner and over a wide range for the measured variables its resultscan serve as a decision-making aid in conducting new experiments. This paper provides three ex-amples of end-to-end assessments of the impact of uncertainty sources involved in the dischargeestimation in open channels using point velocities measured with Acoustic Doppler Velocime-ter. The analyzed uncertainty sources are: a) the sampling duration for velocity measurement,b) the number of points in the verticals, and, c) the number of verticals across the measure-ment cross-section. The raw data for the uncertainty estimations were acquired at the KICTRiver Experiment Center (South Korea), an experimental facility designed for facilitiating quasinatural-scale experiments. The three sources of uncertainties are assembled in practical visu-alization means that can be used for planning the acquisition of new experiments with similarinstruments.

Keywords: uncertainty analysis, type A uncertainty, sensitivity analysis, discharge measurements,

data quality


179



Improvement of uncertainty assessment of discharge estimatedby velocity-area method

Jongmin Kim ∗ 1, Dongsu Kim † 2, Geunsoo Son 2, Du-Han Lee 1

1 KICT, REC – South Korea2 Dankook Univ. – South Korea

ISO 748 has been widely accepted in hydrometry as a prevailing standard for estimationof the uncertainty in discharges determined with the conventional velocity-area method usedin conjunction with point-based velocity acquired in rivers. The ISO 748 standard containscomprehensive look-up tables for the error sources associated with the measurement of velocity,width, and depth involved in the determination of the elemental discharges summed up in thevelocity-area method. While being used for a long time and applied to discharge measurementsacquired in different field conditions, the elemental source estimates are strictly relevant forolder generations of current meters. Moreover, the information on uncertainties assembled ISO748 is aggregated from data acquired in a variety of flow scales, flow regimes, and geometricconditions, thereby it is difficult to relate this information with specific experimental casescharacterized by site-specific flow conditions. The present study aims at rigorously assess threeof the ISO 748 uncertainty sources, i.e., exposure time for a given point-velocity instrument,number of verticals in cross section, and the number of point-velocity collected in a vertical.These measurement error sources are the most important from practical perspective as thedecisions on these parameters are decided by the instrument operators when the measurementis taken. The uncertainties estimates were determined from a customized experiment withAcoustic Doppler Velocimeter (ADV) conducted in one of the KICT River Experiment Center’soutdoor open channels. The obtained results are quite different from the homologous comparedof the ISO look-up tables.

Keywords: Discharge Measurement Uncertainty, ISO, 748, ISO, 1088, VelocityArea Method


180



Friday 7 September

10:55 – 12:35

BC 8 – Mixing processes . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

Me 8 – River management and restoration . . . . . . . . . . . . . . . . 187

Li 8 – Investigating bedload processes . . . . . . . . . . . . . . . . . . . 193

Br 8 – Innovative in-situ measurements (discharge) – part 1 . . . . . 198

181

Friday 7 September, 10:55 – 12:35 BC 8 – Mixing processes

Longitudinal dispersion coefficient in compound open channelwith rigid vegetation on flood plain

Alireza Keshavarzi ∗† 1,2

1 Shiraz University – Water Department, Shiraz – Iran2 Western Sydney University (WSU) – Australia

The longitudinal dispersion is a key element in determining the distribution of pollutant inwaterways which controls the transmission of pollution when cross-sectional mixing is occurred.Social and economic consequences resulting from the direct and indirect consumption of contam-inated water has increased the importance of water quality control. Furthermore, Vegetationcan be a significant agent for improving water quality and reducing the concentration of pollu-tants therefor the investigation of longitudinal dispersion coefficient in vegetated flows is quiteessential. The focus of this study is on the effect of rigid vegetation characteristic (arrangement)and relative depths on longitudinal dispersion coefficient in a rectangular laboratory flume withcompound cross section. Cylindrical piles with 5 mm diameter were planted on the flood plain inorder to model rigid vegetation. Potassium permanganate (KMnO4) has been used as a conser-vative tracer. Digital image processing technique with imaging from tracer cloud in MATLABwas used for measuring tracer concentration in three sections downstream of the injection. Theresults indicated that vegetation could be highly influential on longitudinal dispersion. As thetracer cloud moves downstream the maximum value of tracer concentration decreases up to 66%in a specific relative depth (Dr=0.56).The longitudinal dispersion values in tandem and patcharrangement were found to be 39.2% and 86.6% greater than those in non-vegetated tests. Also,for all vegetation conditions in this study, the longitudinal dispersion coefficient increases withincreasing the relative depth. Moreover, in a specific relative depth the longitudinal dispersioncoefficient increases in patch arrangement with regard to tandem arrangement.

Keywords: Compound open channel, Digital Image Processing, Tracer Cloud, Longitudinal Dis-

persion Coefficient


182



Impact of initial conditions on the prediction of the spread ofthermal pollution in rivers

Monika Kalinowska ∗† 1, Pawe l Rowinski 1, Artur Magnuszewski 2

1 Institute of Geophysics, Polish Academy of Sciences (IG PAS) – Ksiecia Janusza 64, 01-452 Warsaw –Poland

2 University of Warsaw, Faculty of Geography and Regional Studies – Krakowskie Przedmiescie 30,00-927 Warszawa – Poland

The influence of initial conditions on the prediction of the increase of river temperaturebelow the point of release of heated water for a designed power plant has been analysed inthis study. The results for different assumed values of river flow and different temperatures ofthe discharged heated water have been presented. The results have been analysed taking intoaccount existing legal frames. The two-dimensional in-house RivMix model has been used tosimulate the temperature distribution whereas the two-dimensional depth-averaged turbulentopen channel flow model CCHE2D has been used to simulate the velocity fields and the waterdepths for the selected flows of the river.

Keywords: thermal pollution, RivMix model, heat transport, cooling water, mid field zone, Envi-

ronmental Impact Assessment


183



Turbulent flow dynamics and mass transport processes in anatural surface storage zone using field data and numerical

simulations

Jorge Sandoval ∗† 1, Cristian Escauriaza 1, Emmanuel Mignot 2, Luca Mao 3

1 Hydraulics and Environmental Engineering Department (DIHA) – Santiago – Chile2 Laboratoire de Mecanique des Fluides et d’Acoustique (LMFA) – CNRS : UMR5509, Univ. C.

Bernard, Ecole Centrale Lyon, INSA – 36 Av Guy de Collongue 69134 Ecully cedex – France3 Pontificia Universidad Catolica de Chile – Chile

Flow that develops in surface storage zones (SSZ) in rivers is very important for many physi-cal and biogeochemical processes. These regions are characterized by low velocities compared tothe flow in the main channel, and long residence times that favor the deposition of contaminants,nutrient uptake and interactions with reactive sediments. The dynamics of the turbulent flowsin these zones is very complex, typically characterized by a shear layer that induces a recirculat-ing area, with multiple large-scale coherent structures of different temporal and spatial scales.Flow dynamics between the main channel and the SSZ has been widely studied both numericallyand experimentally, however, limited work has been carried out to analyze the turbulent flowfeatures and mass transport mechanisms in natural SSZ at high Reynolds numbers.In this work we analyze the flow in a natural SSZ of the Lluta River, located in northern Chile inthe high altitude Andean environment known as the Altiplano ( ˜4,000 masl). The Lluta Riveris an important water source for many agricultural communities and urban centers located inthe lower parts of the watershed. Although it constitutes an important resource for humanactivities and downstream ecosystems, water quality is affected by the presence of several toxicelements, especially arsenic. This is a consequence of hydrothermal sources and volcanic activityin the higher part of the basin, and the legacy of sulfur mining in the region.We characterize the large-scale turbulent coherent structures using field measurements and 3Dnumerical simulations. We measured the detailed topography, 3D velocity components in severalpoints and the surface velocity field. Topography was obtained through DGPS and digital imageprocessing. The 3D velocity field was measured with an acoustic Doppler velocimeter (ADV),and surface velocity data was obtained through the LSPIV technique.With the field data, we perform numerical simulations using a DES turbulence model coupledwith a 3D passive scalar transport model for Re=45,800. We focus on the coherent structure dy-namics in the shear layer, as the main mechanism that drives the mass and momentum transportprocesses between the SSZ and the main channel. We also analyze the 2D vortical structuresof the mean flow within the lateral cavity, since they have a strong influence in mass transport,increasing mean residence time due to their lower velocities and longer exchange timescales.Finally, we analyze the statistics of mass exchange and residence times in the SSZ, and theperformance of two simplified transport models to represent the mass transport dynamics atlarger scales.

Keywords: surface storage zone, shear layer, coherent structures, residence time, transient storage

models


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Flow and turbulence driven water surface roughness and gasexchange velocity in streams

Christian Noss ∗† 1, Pascal Bodmer 1, Kaan Koca 1, Andreas Lorke 1

1 Institute for Environmental Sciences, University of Koblenz-Landau – Fortstrasse 7 76829 Landau –Germany

Air-water gas exchange controls fluxes of atmospheric gases in and out of rivers and streams.The gas exchange velocity is commonly related to the turbulence and (coherent) flow structuresat the water side. Similarly, river flow hydraulics influences the water surface roughness, whichis frequently used (in terms of surface flow types) for eco- and morphological mapping of spatialvariations of hydraulic conditions. We investigated the relationships between gas exchangevelocity (k600) of carbon dioxide (CO2), water surface roughness and flow hydraulics at differentsurface flow types in a stream in the Palatinate Forest (southwest Germany). We used a fluxchamber and dissolved CO2 concentration of the surface water for k600 calculations, a freelyfloating sphere (equipped with acceleration sensors) to measure water surface roughness as well asan acoustic Doppler and a field-particle image velocimeter for flow and turbulence measurements.The results show an increase in all measured quantities (k600: 7.5 to 13.3 m/d; surface roughnessin terms of standard deviations of accelerations: 0.1 to 2.2 m/sˆ2; mean flow velocity: 0.17 to0.76 m/s; energy dissipation rate: 10ˆ-4 to 10ˆ-2 W/kg) from the flow types ‘smooth boundaryturbulence’ to ‘unbroken standing wave’ sections. Flow and turbulence characteristics of ‘smoothboundary turbulence’ and ‘rippled’ flows were similar, while the turbulence was anisotropicin the ‘unbroken standing wave’ section, and the differences in all parameters between thisand the ‘rippled’ section were large. Additional k600 and surface roughness measurements at‘broken standing waves’ reveal highest values (29.7 m/d and 5.3 m/sˆ2, respectively). Fromcomparison of our results with the small-eddy model and previous studies on the scaling factor,we can demonstrate that gas exchange velocity in the investigated stream followed the sameuniversal dependence on turbulence dissipation rates as observed in wind-driven systems. Wefurther explored the potential of using surface flow type evaluations and water surface roughness(through acceleration) measurements for estimating gas exchange velocities at the reach scaleand beyond.

Keywords: gas fluxes, air, water interface, surface flow types, field measurement, PIV, ADV


185



Mixing processes at an ice-covered river confluence

Pascale Biron ∗† 1, Thomas Buffin-Belanger 2, Nancy Martel 2

1 Concordia University - Department of Geography, Planning and Environment – Montreal, QC –Canada

2 Universite du Quebec - Departement de biologie, chimie et geographie (UQAR) – 300, allee desUrsulines, C.P. 3300, succ. A, Rimouski G5L 3A1, QC – Canada

River confluences are characterized by a complex mixing zone with three-dimensional tur-bulent structures. The position of the mixing interface and the type of flow structures areinfluenced by the junction angle, the momentum flux ratio (Mr) and bed morphology. In coldregions where an ice cover is present for most of the winter period, mixing processes are alsolikely affected by the roughness effect of the ice. However, very few studies have examined theimpact of an ice cover on the flow structure at a confluence. The objective of this study is tocharacterize and compare the flow structure in the mixing zone at a river confluence with andwithout an ice cover. The field site is a medium-sized discordant-bed confluence (around 40 mwide) between the Mitis and Neigette Rivers in the Bas-Saint-Laurent region, Quebec (Canada).The confluence was selected because a thick ice cover is present for most of the winter allowingfor safe field work. A winter field campaign was conducted in 2015 to obtain ice cover mea-surements, hydraulic and morphological measurements. Detailed velocity profiles were collectedat eight locations along the mixing plane with an Acoustic Doppler Velocimeter (ADV) at 25Hz for two minutes to analyze the instantaneous three-dimensional flow structure. Longer (20-minute) time series were also collected to conduct spectral analysis of the velocity signals. Forthe ice-free conditions, drone imagery was used to characterize the mixing layer structures forvarious flow stages, as the turbidity difference between the two rivers allows excellent visual-ization of the coherent Kelvin-Helmholtz vortices present in the mixing zone. Results indicatethat during the ice-free conditions, very large coherent structures (Kelvin-Helmholtz) are visible,and occupy up to 25% of the width of the parent channel. Velocity measurements reveal thatthe ice cover affects velocity profiles by moving the highest velocities towards the center of theprofiles. Large turbulent structures (periodicity of around 10-15 s, corresponding to around 10m) are visible in both the streamwise and lateral velocity components. The strong correlationbetween the streamwise and lateral components illustrates that Kelvin-Helmholtz vortices arethe dominating coherent structures in the mixing zone. The presence of an ice cover affects themean streamwise velocity, but it also has a major impact on the lateral size of mixing layer vor-tices. These findings reveal that lateral velocity structures should be investigated more closelyto improve our understanding or mixing processes at confluences, as instantaneous velocity fluc-tuations in this component are seldom examined at natural river junctions. A spatio-temporalconceptual model is presented to illustrate the main differences on the three-dimensional flowstructure at the river confluence with and without the ice cover.

Keywords: Confluence, Ice cover, Mixing zone, Three, dimensional turbulent structure, Kelvin,

Helmholtz vortices


186


Friday 7 September, 10:55 – 12:35 Me 8 – River management and restoration

Morphodynamic effects of stone and wooden groynes in arestored river reach

Bahaeldeen Zaid ∗† 1, Paride Nardone 1, Michael Nones 2, Christoph Gerstgraser 3,Katinka Koll 1

1 Leichtweiß-Institut fur Wasserbau, TU Braunschweig, Beethovenstraße 51a 38106 Braunschweig –Germany

2 Interdepartmental Centre for Industrial Research in Building and Construction - Fluid DynamicsUnit, University of Bologna, Via del Lazzaretto 15/5, 40131 Bologna – Italy

3 Ingenieurburo fur Renaturierung, An der Pastoa 13 03042 Cottbus – Germany

Restoration works on an 11 km long reach of the Spree River near Cottbus in Germanywere accomplished in 2014. The overall objective was to improve the biodiversity, changing themorphological structure from a straight single-thread river to a braiding one with reshaped thal-weg, and creating zones with varying flow velocities required for fish spawning. To accomplishthis, several groynes were constructed along the reach. Two types of groynes were used (stonegroynes and groynes with large wooden trunks). The stone groynes are impermeable and thecrest is inclined so that only the tip is typically submerged during normal flow conditions. Awooden groyne consists of several trunks arranged vertically allowing the flow to pass betweenthe trunks. The trunks are fixed to the bank and to wooden piles up- and downstream of the tip.The wooden groynes are mainly submerged at normal flow conditions. Two groynes, a stone anda wooden one, were selected to compare the local morphodynamic effects caused by the differenttypes. Therefore, a straight site was selected with a stone groyne on the left river bank and awooden groyne about 110 m downstream on the right bank. The flow velocity was measuredwith a fine grid around the groynes and with a courser grid over the entire cross-section andfor distances of 12 m and 16 m upstream and downstream of the groynes, respectively. Thevertical profile was captured by measuring at five levels above the bed. The bed topographywas measured at the same locations of the velocity measurements. Bed material was sampled atseveral locations around the groynes, aiming to determine local sediment characteristics. Theresults of the analysis of the flow velocity measurements, bed topography and bed material dataof both groynes will be presented and the comparison of the effect of each groyne type on theriver morphodynamics will be discussed.

Keywords: restoration, stone groyne, wooden groyne, flow field, morphology


187



River improvement techniques for mitigating river beddegradation and channel width reduction in the sandy Hii River

where sediment transport occurs at normal times

Gotoh Takahisa ∗† 1, Shoji Fukuoka 1

1 Res. & Devpt Init., Chuo University – 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 – Japan

The goal of this research is that provides the idea of river improvement techniques for stabi-lizing river bed elevations and river channel shapes in the sandy braided rivers where sedimentsupplies from the upper river basins are almost zero at normal discharge conditions.The Hii River located at the Izumo alluvial plain having more than 20 m depth of the alluviumwas originally the braided river. However, bed elevations have degraded and channel widthsreduced for the past about 20 years. For these phenomena, the braided channels have beenchanged to the meandering channel because the channel widths became narrower.Firstly, we investigated causes of the bed degradation and the channel width reduction by usingannual survey data, aerial photographs and construction records of the river structures in theHii River.The bed material of the Hii River is sand of about 1 to 2 mm in diameter. The bed slope is about1/600 and the bed is covered with sand waves. Thus, the sand on the river beds is transportedactively during the normal discharge conditions. We confirmed that the shear stress acting onthe river beds was about 3 to 5 times of the critical shear stress in the main channel duringthe normal discharge. And, the Igaya ground sill has prevented sediments transported from theupstream during the normal discharge. Thus, the river bed degradation has progressed in themain channels at the downstream section of the ground sill. The bed degradation has reducedthe width of the main channel and brought the formation of flood channels. The narrowed mainchannel led to advance the further river bed degradation.On the other hands, sediment materials were transported by flood flows across the ground silland deposited at the downstream section of the ground sill in flood periods. We found out thatthe sediment passing through the ground sill due to flood flows mitigated the bed degradationand the reduction of main channel width in the downstream of the ground sill.Secondly, we proposed river improvement techniques of sediment replenishment from the up-stream of the Igaya ground sill to its downstream and design of the lateral and longitudinal shapesof the channels. The proposed channel shapes were designed based on the braided channel seenin the past Hii River. And, for sediment supply to the degraded sections in the downstream ofthe ground sill, we attempted to replenish sediments to the main channel downstream of theIgaya ground sill by lowering elevation of central part of the the ground sill.Our proposed river improvement techniques were examined and determined by using numer-ical simulations of bed variations due to repetitions of the normal discharge flows and floodflows. The BVC Method (the Bottom Velocity Computational Method, Uchida and Fukuoka,Advances in Water Resources, 2014) which were able to estimate vertical velocity distributionsof flows based on the depth integrated model were employed for simulating flows and sedimenttransports. The numerical simulations were conducted for long term period including the flooddischarge and the normal discharge in the Hii River.Consequently, our numerical simulations demonstrated that the proposed river improvementtechniques were able to mitigate the bed degradation and the reduction in the channel widthin downstream sections of the ground sill for next about 10 years. The sediment materials atthe upstream of the ground sill were replenished to the downstream by lowering elevation of the


188



central part of the Igaya grond sill. Thus, we presented that the lowering elevation of the centralpart of the grond sill were effective for recovery of degraded river sections at the downstream ofthe ground sill.

Keywords: sandy braided river, river bed degradation, channel width reduction, sediment replen-

ishment, river improvement technique

189


On the morphological evolution of restored banks: case study ofthe Meuse river

Gonzalo Duro ∗† 1, Alessandra Crosato 1,2, Maarten Kleinhans 3, Wim Uijttewaal 1

1 Delft University of Technology (TU Delft) – Building 23, Stevinweg 1, 2628 CN, Delft – TheNetherlands

2 IHE Delft Institute for Water Education (IHE Delft) – Westvest 7, Delft – The Netherlands3 Utrecht University (Faculty of Geosciences) – PO box 80115, 3508 TC, Utrecht – The Netherlands

In recent years, many riverbanks in Europe had their protections removed to reactivatenatural erosion processes and improve riparian habitats. Yet, other river functions may beaffected, such as navigation and flood conveyance. The quantification and prediction of erosionrates and volumes is then relevant to manage and control the integrity of all river functions. Thiswork studies the morphological evolution of riverbanks along two restored reaches of the MeuseRiver in the Netherlands, which are taken as case studies. This river is an important navigationroute and for this its water level is strongly regulated with weirs. Through aerial photographsand two airborne LIDAR surveys, we analysed the evolution over nine years of restoration andreconstructed the topography along 2.2 km. of banks. An extraordinary low-water level after aship accident provided the opportunity to observe and measure the bank toe. The banks showa terrace of erosion close to the normally regulated water level, highly irregular erosion ratesup to 7 m/year, embayments evolving with upstream and downstream shifts, and sub-reacheswith uniform erosion. Probable causes of erosion include ship-waves, high water flows and waterlevel fluctuations. Distinct patterns might be explained by the presence of riparian trees andsoil strata of different compositions. These intriguing case studies will continue to be studiedto disentangle the role of different erosion drivers, predict erosion magnitudes and establishwhether bank erosion will stop or continue in the future.

Keywords: Riverbanks, restoration, erosion, morphology


190



Numerical groyne layout optimisation for restoration projects inlarge rivers: An adaptive approach towards a desired

morhpodynamic equilibrium

Martin Glas ∗† 1, Michael Tritthart 1,2, Marcel Liedermann 1,2, Sebastian Pessenlehner 1,Helmut Habersack 1

1 Institute of Water Management, Hydrology and Hydraulic Engineering, Department of Water,Atmosphere and Environment, BOKU—University of Natural Resources and Life Sciences Vienna –

Muthgasse 107, A-1190 Vienna – Austria2 Christian Doppler Laboratory for Sediment Research and Management – Austria

Integrative restoration measures at large rivers target the improvement of morphological andecological conditions, under consideration of economic demands, specifically navigational ones.Alternative groyne layouts with e.g. reduced groyne spacing and lowered crest elevation reduceecological deficits and have the potential to cease frequently encountered river bed incision ofheavily modified rivers. On the other hand, the induced change in the morphodynamic equi-librium may interfere with navigation by reducing the water depth in the fairway. In 2009, apilot project was realised on the Austrian Danube, including an alternative groyne layout. As aconsequence the desired aggradations in the fairway became too large, leading to an increaseddredging effort. In 2014, a numerical groyne optimisation, specifically a 3D numerical modelin combination with a sediment transport model, was applied. In 2015, after implementing theoptimised groyne layout in the field, morphodynamic equilibrium was reached reducing the needof extensive dredging. This equilibrium could be shown by analysing subsequently observedbathymetries until 2017. Moreover, the morphodynamic changes due to the groyne optimisa-tion in 2015 were reproduced successfully with the numerical models. Thus they represent acost effective tool for planning and optimising future restoration measures in large and heavilymodified rivers.

Keywords: numerical models, groynes, restoration, morphodynamics, large river


191



Development and implementation of ecological and economicalflood protection measures at an alpine river

Ursula Stephan ∗† 1, Silke Kainz 1, Michael Hengl 1, Alexander Bickel 2

1 Inst. Hydraulic Eng. Calib. of Hydrometrical Current-Meters – Severingasse 7 A-1090 Wien – Austria2 Breuß Mahr Bauingenieure GmbH – Werben 19 A-6842 Koblach – Austria

The river Lutz in Vorarlberg/Austria was forced into a straight and narrow river bed inthe 1920ies. Several weirs with heights ranging from 0.5 to 2.5 m were erected to stabilisethe river bed, but which, too, impeded organism passability. After decades with several floodsthe protection measures were in bad condition. In 2005, a 500-years flood caused heavy damagealong the river and destroyed a main railway line. This incident initiated comprehensive planningactivities to improve both, the flood protection as well as the ecological status of the river. Theconcerned river section is 1600 m long and situated between Ludesch and Thuringen. Severaltechnical proposals focussing on stabilising the river bed, increasing the discharge capacity andimproving the ecological status were to be optimised in a physical model: (1) a step-pool-ramp sloped 4 % with a variable width including a low-flow-channel and a downstream scourprotection, (2) an open rip-rap (revetment) sloped 1.3 % including a low-flow-channel and largeboulders as additional structure elements, (3) an increased river width by 45 % and embankmentssloped 1:3 instead of 1:1.3 to increase the discharge capacity, (4) embankment groynes as anecological and dynamic bank protection instead of a bank reinforcement.The physical model was built with movable river bed and banks. The main goals of the physicalmodel were to test the proposed construction types for feasibility, observe the failure mechanismin case of extreme floods, optimise boulder sizes and quantities, optimise the groyne geometryand interval to minimise bank erosion and to observe the behavior especially of the low-flow-channel in case of sediment transport. 13 experimental series lead to a significantly changeddesign of the proposed measures compared to the original planning. The main changes concerned(1) the optimisation of stone and boulder sizes of step-pool-ramp including the downstream scourprotection, open rip-rap and embankment groynes, (2) an optimised cover density of the openrip-rap ensuring a balanced ratio between the cost-minimising amount of cover stones and theneeded river bed protection, (3) the design of the embankment groynes and (4) the design ofthe proposed curved geometry of the low-flow-channel which was turned into a straight oneconcentrating the flow in the middle of the cross section to prevent sediment deposition in caseof sediment transport.Implementing these changes the proposed bed stabilization and ecological measures proved tobe suitable over the whole range of discharges up to the design flood (HQ300 - 250 m3/s).Overloading by an extreme flood event (HQ500) caused merely minor and local damage suchas a slight mobilization of the open rip-rap and slowly progressing depth erosion. Boulder sizesas well as material requirement could significantly be reduced. The proposed design of theembankment groynes led to a certain but acceptable amount of bank erosion in the straightriver section, but had to be adapted in the bend due to the scour development near the head ofthe groynes. Organism passability also in case of very low flow situations could be guaranteeddue to the re-designed low-water-channel. All measures were successfully implemented in winter2015/16 and led to cost-savings which exceeded the model costs by 6-times.

Keywords: flood protection, bank protection, ecological flood protection measures, river bed sta-

bilisation


192


Friday 7 September, 10:55 – 12:35 Li 8 – Investigating bedload processes

A PIV-based method to measure spatial gradients in bedloadtransport over a dune

Renske Terwisscha van Scheltinga ∗ 1, Heide Friedrich † 1, Giovanni Coco 1

1 University of Auckland – Level 4, Faculty of Engineering Building 20 Symonds Street, Auckland –New Zealand

Traditional sediment transport equations calculate sediment flux from bed shear stress andthe equations predict that transport increases nonlinearly with an increase in flow velocity. Ina dune field, the dune geometry affects the flow velocity causing accelerating flow over the dunecrest and de- and reattachment of the flow downstream of the dune crest. Sediment flux pre-dicted from the reach-averaged bed shear stress gives fairly good results for dune fields, thoughtheir simplification is discordant for the complexity of the processes involved. Measurements ofthe displacement of sand particles over the dune bed were derived from high-frequency imagecapturing. The two main methods to measure particle velocities from images are particle track-ing velocimetry (PTV) and particle image velocimetry (PIV). We compare individual particletracking with a PIV-based correlation method. The PIV-based method promises to be a moreefficient and effective approach to track particle motion. It is more suitable for the conditionsof high bedload transport, as present in our experiments. The PIV-based method is based onusing images of difference (IoD) and is fully automated and identifies spatial gradients at asupport scale in the order of centimetres. Findings align with our general knowledge of accel-erating flow over the dune crest. The mean streamwise particle velocity and activity over adune stoss slope increase. At the scale of 0.026 m the observed particle velocity variability canbe explained in the context of general onset and cessation of sediment transport, the effect ofthe reattachment zone and observed sweep/burst events. By decreasing the streamwise distancebetween cross-sections, the variations in mean particle velocity induced by superimposed beddefects are distinguished as well. The maximum particle velocity and activity occurred at thesame location and consequently the location of the maximum transport over the dune crest wasidentified. The measurements bridge the gap between individual particle motion studies and(non-local) sediment transport flux measurements.

Keywords: sediment transport, subaqueous dunes, high frequency image capturing, PIV, particle

motion


193



Grain and bedform roughness properties isolated fromgravel-patch DEMs

Stephane Bertin 1, Jane Groom 1, Heide Friedrich ∗† 1

1 University of Auckland – Level 4, Faculty of Engineering Building 20 Symonds Street, Auckland –New Zealand

Remote sensing of gravel-bed patches and resulting high-resolution digital elevation models(DEMs) allow identification of various spatial scales of surface roughness, improving on tradi-tional roughness parameterization based on sediment size. Thus far, spatial scales of gravel-bedroughness have been examined using semivariograms or equivalent structure/autocorrelationfunctions, from which dimensions relating to grain and bedform roughness scales have been de-termined. However, it is difficult to clearly differentiate roughness scales and separate analysisof roughness properties is not possible. This study examines the use of moving-window de-trending on gravel-patch DEMs for isolating grain and bedform roughness and their respectivetopographic signatures. An extensive dataset of water-worked gravel surfaces collected in bothlaboratory and field environments is used. The measured bed topography is separated into twodistinct DEMs: one representing grains, the other representing bedforms. Roughness propertiessuch as the standard deviation of bed elevations representing vertical roughness, imbrication,and spatial correlations are determined separately for grains and bedforms. The results showthat both roughness scales are controlled by the size of the coarse sediment forming the bedsurface, with positive linear relationships connecting bed composition and vertical roughness.Coarse sediment is controlling bedform development by forming humps on the surface, in thelee of which finer sediment is sheltered. We present synthesis relationships connecting verti-cal roughness of gravel patches to the vertical roughness of grains and bedforms. This is animportant finding as it provides (i) an opportunity to reconstruct (or parameterise) the bedmicrotopography from the simple bed configurations used as input for flow modelling studies,helping to obtain realistic flow turbulence information; (ii) new means to compare surface rough-ness of gravel-bed rivers measured across studies; and (iii) novel information relevant to furtherour understanding of the complex mechanisms involved during streambed armouring.

Keywords: gravel, bed, roughness, bedforms, DEMs


194



Experimental observations on sorting patterns of heterogeneoussediment mixtures in low constrained flows

Costanza Carbonari ∗† 1,2, Francesco Tanganelli 1,2, Alain Recking 2, Luca Solari 1

1 Dipartimento di Ingegneria Civile e Ambientale, Universita degli Studi di Firenze – Via di S. Marta 3,50139 Firenze, Italy

2 Irstea centre de Grenoble, UR ETNA – 2 rue de la Papeterie, 38402 St-Martin-d’Heres – France

River beds present different size fractions of sediments which differently interact with flow:during bed load transport, heterogeneous sediment mixtures undergo the process of sorting sothat the grain size distribution of river beds displays significant spatial structures, both in thesurface texture and in the stratigraphy. Patches, which are surface facies of similar grain size;armor; and stratigraphic signature of sediment deposits play an important role considering riverbed forms and in general morphodynamics; and this applies to all stream morphologies.The case of gravel bed rivers typically characterized by bimodal sediment mixtures is of partic-ular interest since sorting can concern the vertical grain size structure as well as those in thestreamwise and spanwise directions. In fact, in this kind of streams the presence of an alluvialbed with mobile banks, moderate slope, and a weak mobility of the coarse sediment fractionmakes it possible for the active bed to evolve also in the plane (both longitudinal and lateraldirections), whereas it is not the case for more confined, steeper streams. In not highly confinedgravel bed rivers is therefore possible to observe both slope and width adjustments and theircomplex mutual dependence on vertical and planimetric sediment sorting. Active channel varia-tions and heterogeneous sediment sorting also interact with bed forms, affecting their formation,morphology and migration, as it has been observed in bars (Lisle et al., 1991; Lanzoni, 2000)and in braided patterns (Leduc, 2013).Narrow flume experiments investigated interactions between channel slope adjustments, verticalsorting, and fluctuations of bed load transport rate at length (Recking et al., 2009; Bacchi etal., 2014); on the other hand, only a few studies considered channel width variations related tosediment sorting in poorly confined flows. It seemed therefore interesting to explore further howsediment sorting and channel morphology interact at varying flow constraint. With this aim wecarried out new laboratory experiments in a wider flume that allows flow deviation.The tilting flume is 6 meter long and has a maximum width of 0.5 meters. We used a bi-modal sediment mixture; constant sediment feed rate and constant water discharge. We carriedout accurate measurements and analysis on bed topography using Structure from Motion pho-togrammetry and on bed surface texture using digital image processing. We also performedLarge Scale Particle Image Velocimetry to determine water surface velocity fields.

Keywords: sediment sorting, bimodal sediment mixture, bed load transport


195



Vertical grain size sorting in bedload transport on steep slopeswith a coupled fluid-discrete element model

Philippe Frey ∗† 1,2, Remi Chassagne 1,2, Raphael Maurin 3, Julien Chauchat 2,4

1 Irstea centre de Grenoble, UR ETNA – France2 Universite Grenoble Alpes (UGA) – France

3 Institut de Mecanique des Fluides de Toulouse – Univ. de Toulouse, INPT, UPS – France4 Lab. Ecoulements Geophysiques et Industriels (LEGI) – Univ. Joseph Fourier - Grenoble 1, INPG,

CNRS : UMR5519 – France

Bedload, the coarser material transported by the turbulent flow in stream channels, incontact with the bed, has major consequences for public safety, for the management of waterresources, and for environmental sustainability. Most particularly, in mountains, steep slopesdrive intense transport of a wide range of grain sizes. An important reason for our limited abilityto predict sediment flux is the absence of general understanding of grain-grain interactions instream channels, in particular related to the size sorting process (Frey and Church 2009). Whenthe coarse bed is moving, the so-called ‘kinetic sieving’ process occurs, where the void openingsdue to grain motion permit downward percolation of larger particles than under the mere effectof gravity.In order to gain understanding of this process, bedload transport numerical experiments oftwo-size particle mixtures were carried out, using a coupled Eulerian-Lagrangian fluid-discreteelement model developed at Irstea and validated with experiments (Maurin et al. 2015, 2016).It is composed of a three dimensional discrete element model (based on the open source codeYade), describing each individual particle, coupled with a one dimensional Reynolds averageNavier Stokes model (Chauchat 2017). A 3D domain consisting at initial time of a given numberof layers of 4 mm spherical particles deposited on top of a 6 mm particle bed, were submitted toa water flow and let evolved with time. The flow is turbulent (bulk Reynolds number of about104), hydraulically rough (Particle Reynolds of order 103), supercritical (Froude greater than 1)and the dimensionless water shear stress (Shields number) is between 0.1 and 0.3. A slope of0.1 was considered (angle of 5.71◦).For a given Shields number, the elevation of the center of mass of the infiltrated fine particleshas been shown to remarkably follow the same logarithmic decrease with time, whatever thenumber of fine layers initially deposited. This decrease is steeper for a higher Shields number.This common collective behavior is shown to be related at first order to the granular shear ratedepth profile, exhibiting an exponential decrease.A better understanding of bedload size sorting poorly known processes will ultimately improvesediment transport and river morphology modelling.

Keywords: sediment transport, bedload, size sorting, particle scale, discrete element model


196



Stress balance for a viscous flow with a single rolling particle

Edward Biegert ∗ 1, Bernhard Vowinckel † 1, Leina Hua 2, Eckart Meiburg 1

1 Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106-5070 –United States

2 State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, ChineseAcademy of Sciences (IPE-CAS) 1 North 2nd Street, Zhongguancun, Haidian District 100190 Beijing –

China

Contribution to the special session porosity modelsOne of the most important aspects in hydraulic engineering is to describe flows over mobileporous media in a continuum sense to derive models for sediment transport. This remains achallenging task due to the complex coupling of the particle and the fluid phase. ComputationalFluid Dynamics can provide the data needed to understand the coupling of the two phases. Tothis end, we carry out grain-resolving Direct Numerical Simulations of multiphase flow. Theparticle phase is introduced by the Immersed Boundary Method and the particle-particle inter-action is described by a sophisticated Discrete Element Method. We derive the stress budgetsof the fluid and the particle phases separately through a rigorous analysis of the governing equa-tions using the Double Averaging Methodology and the Coarse-Graining Method. As a nextstep, we perform a simple simulation of a heavy particle exposed to a Poiseuille flow rollingalong a wall to understand the physical implications of the fluid-particle coupling. All terms ofthe stress balances can be computed in a straightforward manner allowing to close the budgetsfor the two phases separately. However, we encounter problems when attempting to combinethe fluid-resolved local stresses with the coarse-grained particle stresses into a single balance forthe fluid-particle mixture.

Keywords: Sediment transport, Momemtum balance, Double Averaging Methodology, Coarse

Graining Method


197


Friday 7 September, 10:55 – 12:35 Br 8 – Innovative in-situ measurements – part 1

Bedload measurements on large rivers in the United States

David Abraham ∗† 1, Tate Mcalpin 1, Keaton Jones 1

1 – 3909 Halls Ferry Rd, Vicksburg MS 39180, United States

The movement of bed forms (sand dunes) in large sand-bed rivers is being used to determinethe transport rate of bed load. The ISSDOTv2 (Integrated Section Surface Difference OverTime version2) methodology uses time sequenced differences of measured bathymetric surfacesto compute the transport rate. The method was verified using flume studies, and more recentlyhas been compared against several transport functions. In general, the method provides veryconsistent and repeatable results, and also shows very good fidelity with most other measurementtechniques. Over the last 7 years we have measured, computed and compiled what we believe tobe the most extensive data set anywhere of bed load measurements on large sand bed rivers. Mostof the measurements have been taken on the Mississippi, Missouri, Ohio and Snake Rivers in theUnited States. For cases where multiple measurements were made at varying flow rates, bed-load rating curves have been produced. This paper will provide references for the methodology,but will be intended more to discuss the measurements, the resulting data sets, and current andpotential uses for the bedload data.

Keywords: Bedload, dunes, large rivers


198



Shore-based monitoring of flow dynamics in a steep bedrockcanyon river

Saber Ansari ∗† 1, Colin Rennie 1, Jeremy Venditti 2, Eva Kwoll 3, Kirsti Fairweather 2

1 Civil Engineering Department, University of Ottawa – Canada2 Department of Geography, Simon Fraser University – Canada3 Department of Geography, University of Victoria – Canada

The pace of landscape evolution is set by bedrock erosion in canyons. This phenomenonoccurs by various geological processes including plucking of bedrock blocks and abrasion bysaltating bedload and suspended load in highly turbulent flows. For a better understandingof the river flow characteristics in bedrock rivers, a comprehensive study of flow dynamics wasundertaken in Black Canyon in the Fraser River, British Columbia. We used shore-based videoimagery of the river to study surface flow dynamics. The shore-based monitoring system con-sisted of a Campbell Scientific camera mounted at the top of the canyon walls. We monitoredthe water surface boils due to upwelling and determined river surface flow velocities from theshore-based imagery. Automatic detection of the upwelling surface boils leads to a better un-derstanding of the secondary circulation patterns and flow structures in this large steep riverbedrock canyon. The data collection and analytical procedures developed in this research arecost-effective tools for remotely determining flow dynamics, which can be applied to other rivers.

Keywords: Bedrock canyons, Shore based imagery, Turbulent flow


199



Estimating uncertainties in hydraulically-modelled rating curvesfor discharge time series assessment

Valentin Mansanarez ∗† 1,2, Ida Westerberg 3, Steve Lyon 1,2, Norris Lam 1,2

1 Department of Physical Geography, Stockholm University (SU) – SE-106 91 Stockholm – Sweden2 Bolin Centre for Climate Research (BBCC) – Stockholm University, SE-106 91 Stockholm, Sweden,

Sweden3 IVL Swedish Environmental Research Institute (IVL) – Valhallavagen 81 114 27 Stockholm – Sweden

Establishing a reliable stage–discharge (SD) rating curve for calculating discharge at a hy-drological gauging station normally takes years of data collection. Estimation of high flowsis particularly difficult as they occur rarely and are often difficult to gauge in practice. At aminimum, hydraulically-modelled rating curves could be derived with as few as two concur-rent SD and water-surface slope measurements at different flow conditions. This means thata reliable rating curve can, potentially, be developed much faster via hydraulic modelling thanusing a traditional rating curve approach based on numerous stage-discharge gaugings. In thisstudy, we use an uncertainty framework based on Bayesian inference and hydraulic modellingfor developing SD rating curves and estimating their uncertainties. The framework incorpo-rates information from both the hydraulic configuration (bed slope, roughness, vegetation) us-ing hydraulic modelling and the information available in the SD observation data (gaugings).Discharge time series are estimated by propagating stage records through the posterior ratingcurve results. Here we apply this novel framework to a Swedish hydrometric station, account-ing for uncertainties in the gaugings and the parameters of the hydraulic model. The aim ofthis study was to assess the impact of using only three gaugings for calibrating the hydraulicmodel on resultant uncertainty estimations within our framework. The results were comparedto prior knowledge, discharge measurements and official discharge estimations and showed thepotential of hydraulically-modelled rating curves for assessing uncertainty at high and mediumflows, while uncertainty at low flows remained high. Uncertainty results estimated using only 3gaugins for the studied site were smaller than +/- 15% for medium and high flows and reducedthe prior uncertainty by a factor of ten on average.

Keywords: River, hydraulic modelling, hydrometry, rating curve, uncertainty assessment


200



Wavenumber-frequency analysis of river surface texture toimprove accuracy of image-based velocimetry

Kojiro Tani ∗ 1, Ichiro Fujita † 1

1 Department of Civil Engineering, Graduate school of Engineering, Kobe University –1-1Rokkodai-cho, Nada, Kobe 657-8501 – Japan

For establishing non-intrusive techniques for river surface flow measurements, video imagesshot from riverbank by a river monitoring camera have been paid attention in the past decadesand the image analysis techniques such as the Large Scale Particle Image Velocimetry (LSPIV)or the Space-Time Image Velocimetry (STIV) have been developed. These two image velocime-tries are also used with airborne images shot from an unmanned aerial vehicle (UAV) or ahelicopter and they were successfully utilized for measuring flood flows in a wide area. Theseimage-based measurement techniques assume that water surface fluctuations made visible as aform of surface texture are advected with the surface flow. However, the assumption sometimesfails when the effect of gravity on the free-surface becomes obvious by the generation of gravitywaves travelling in all directions, which could override the effect by the open-channel turbulence.In laboratory scale experiments of open-channel flows, detailed water surface profiles can be mea-sured by applying sophisticated measurement techniques such as the stereoscopic measurementor the moire interferometry. The combined effects of turbulence and waves can be investigatedby applying the wavenumber-frequency analysis to the space-time expression of the water sur-face fluctuation, from which the turbulence generated profile can be extracted to obtain theadvection speed of the surface fluid.The idea of the present research is that a method similar to the above can be applied to thespace-time image (STI) obtained in the application of STIV for river surface flow measurements.The essential difference of STI from the space-time expression obtained in a laboratory flumeis that the texture appeared in an STI does not directly indicate the water surface fluctuationquantitatively but just displaying the time evolution of image intensity distribution along asearch line set in the streamwise direction. However, assuming that brighter pixel correspondsto a higher water elevation and darker pixel to a lower water elevation in a qualitative manner,a similar approach can be executed to extract only the turbulence generated texture from theoriginal STI.Following the assumption regarding the similarity between the surface texture and the watersurface profile, the procedure to extract the turbulence generated texture from the original STIwas applied to the actual river flood measurement. The target flow was the snowmelt flood ofthe Shinano River, where river surface video images with 4K resolution were captured from UAVand riverbank. The average surface velocity was about 2 to 3 meters per second at the mea-surement site of the Asahi Bridge. In the analysis, the image intensity distribution in STI wasmodified so that the image fluctuations are normalized at every point in the image, which couldimprove the accuracy of the STIV analysis significantly. The measurement at the upstream ofthe Asahi Bridge showed that components generated by surface waves were clearly removed bythe proposed procedure, i.e. an STI with inclined straight texture showing the constant advec-tion speed of the surface flow was obtained, although the influence of the surface wave was notsignificant at the measurement section. The procedure proposed in this research can be usedto improve the accuracy of the river surface flow measurement even when the effect of gravitywaves become predominant by the wind.

Keywords: LSPIV, STIV, wavenumber, frequency analysis, free, surface behavior


201



Development of aerial space time volume velocimetry formeasuring surface velocity vector distribution from UAV

Issei Tsuji ∗ 1, Kojiro Tani 1, Ichiro Fujita † 1, Yuichi Notoya 2

1 Department of Civil Engineering, Kobe University, 1-1 Rokkodai-cho, Nada Kobe 657-8501 – Japan2 CTI Engineering Co., Ltd. – Japan

In recent years, due to the development of UAV, its application to the river engineering suchas the measurement of river topography or river surface flows has been increasing. Regardingthe aerial river flow measurement techniques, the aerial Large Scale Particle Image Velocimetry(LSPIV) and the aerial Space-Time Image Velocimetry (STIV) have been developed by theauthor’s group in the past decade. Both techniques have been successfully applied for severalactual flood flow measurements in Japan. However, the aerial LSPIV could yield erroneousvelocity vectors when the river surface texture moving with the surface flow is not apparentin the image. The aerial STIV is a robust measurement technique compared with the aerialLSPIV but it cannot detect the flow direction intrinsically. To overcome the shortcomings of theprevious image-based techniques, the space volume image velocimetry (STVV) was developedin this research, allowing the measurement of surface velocity vector distributions more stablythan LSPIV.In STVV, the time evolution of image intensity distribution within a rectangular area set ona river surface is expressed as a space time volume (STV) having three axes with two imagecoordinate directions and the time direction. This is an extension of space time image (STI)in the STIV technique. To extract the flow direction and flow velocity from STV, a three-dimensional autocorrelation function (3D-acf) of the image intensity distribution wihin an STVis first calculated. Then the velocity vector is extracted after applying the spherical logarithmictransformation of the 3D-acf.The developed technique was applied to the aerial video images of the snowmelt flood of theShinano River captured from an UAV, hovering step by step to cover a river reach of about 900meters. The most specific feature of the flow at the site is that the main flow is deflected at anintermediate section of the target reach, showing a large change of main flow direction whichis difficult to capture by the aerial STIV. Therefore, the STVV analysis was applied to each ofthe hovering section after stabilizing the images frame by frame with subpixel accuracy. Themeasurement result was compared with various techniques such as aerial LSPIV, aerial STIVand ADCP.As a result of the comparison, it was confirmed that the relative error of flow velocity by STVVis smaller than that of aerial LSPIV showing a more stable two-dimensional velocity vectordistributions. The aerial STIV becomes less reliable when the direction of the flow changesgreatly because it is difficult to set the search lines in the direction of the main flow appropriately.Moreover, the wake flow effect of piers were successfully measured at the downstream region ofthe Asahi Bridge, indicating an extended influence of the wake far downstream of the bridge. Inaddition, the discharge estimated from the surface velocity distribution at an upstream sectionagreed fairly well with the ADCP data. By applying the aerial STVV technique to the UAVimages, much longer river reach measurement becomes possible when there appears surfacetextures following the surface flow.

Keywords: surface flow measurement, STVV, STIV, LSPIV, image analysis, UAV, snowmelt flood


202



Friday 7 September

14:00 – 15:40

BC 9 – Flow resistance over rough bed . . . . . . . . . . . . . . . . . . 204

Me 9 – Bank erosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

Li 9 – Bedload and bed evolution modelling . . . . . . . . . . . . . . . 214

Br 9 – Innovative in-situ measurements (discharge) – part 2 . . . . . 221

203

Friday 7 September, 14:00 – 15:40 BC 9 – Flow resistance over rough bed

Depth-averaged velocity and bed shear stress in unsteady openchannel flow over rough bed

Jnana-Ranjan Khuntia ∗† 1, Kamalini Devi 1, Sebastien Proust 2, Kishanjit K. Khatua 1

1 Civil Engineering Department, National Institute of Technology Rourkela, 769008, Odisha – India2 Irstea centre de Lyon-Villeurbanne, UR RiverLy, 5 rue de la Doua CS 20244, 69625 Villeurbanne –

France

Very few studies have been carried out in the past in estimating depth-averaged velocity andbed shear stress in unsteady flow over rough beds. An experiment is thus conducted to investigatethe vertical and lateral velocity profiles under unsteady flow conditions in a rough open channelfor various flow depths. One hydrogram is repeatedly passed through the rectangular flumewith a fixed rigid grass bed. Using micro Pitot tube and Acoustic Doppler Velocimeter (ADV),the flow patterns are investigated at both lateral and longitudinal positions over different cross-sections. For two typical flow depths, the velocities in both the rising limb and falling limbare observed. Hysteresis effect between stage-discharge (h ˜ Q) rating curve between risingand falling limbs is illustrated. Lateral distribution of depth-averaged velocity and bed shearstress are plotted at three different cross sections and compared with the steady flow conditions.In falling limb of an unsteady flow case, both depth-averaged velocity and bed shear stressdistribution in the central region is higher than that of steady flow case. However, in the risinglimb, the bed shear stress of unsteady flow is less than that of steady flow case. Further, inan unsteady flow, the magnitude of depth-averaged velocity is found to increase towards thedownstream sections. Along the downstream positions, bed shear stress values increase forlower flow depths and decrease for higher flow depth cases.

Keywords: open channel flow, unsteady flow, hydrogram, velocity profiles, depth averaged velocity,

bed shear stress


204



An experimental investigation on the flow resistance over aporous gravel bed surface and its non-porous counterpart

Christy U. Navaratnam ∗† 1, Jochen Aberle 1,2, Jie Qin 3, Pierre-Yves Henry 1

1 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology(NTNU) – S.P. Andersens veg 5, 7491, Trondheim, Norway

2 Leichtweiß-Institut fur Wasserbau, Technische Universitat Braunschweig – 38106, Braunschweig,Germany

3 College of Harbor, Coastal and Offshore Engineering, Hohai University – Nanjing, China

The hydraulic resistance of wall-bounded flows is a topic of great importance for fluvialhydraulics. Its determination has been in the focus of research for many years but still representsa challenge for hydraulic engineers as the roughness of fluvial beds affects flow properties suchas flow velocity distribution, mean velocities, flow rate, and turbulence characteristics. The flowresistance associated with fluvial beds is typically parameterized using ‘roughness’ or ‘friction’factors such as Manning’s n, Chezy’s C, or Darcy-Weisbach’s f , which are interconnected andcan be converted into each other. Roughness and friction factors are usually determined withouttaking the vertical structure of fluvial beds into account, which consists in most cases of a poroussubsurface layer followed by the roughness, logarithmic and outer layer, respectively. Thus, itis tacitly assumed that a porous and non-porous bed having an identical surface structure willcause identical flow resistance. However, various studies carried out with idealized roughnesselements such as spheres provided experimental evidence that a porous bed exhibits a largerresistance to the flow than its impermeable counterpart. Detailed studies to determine theeffect of porosity on flow resistance exerted by natural beds such as gravel bed armor layersare rare since reproducing complex gravel bed surface requires special experimental techniques.This paper presents results from laboratory experiments which were specifically designed todetermine the flow resistance over a water-worked gravel bed and its impermeable counterpart(cast bed). In a first step, the technique used to create the cast bed is introduced followed by thedescription of the experimental setup and procedure to quantify flow resistance over both thewater-worked and cast bed. Moreover, the influence of the grain orientation on flow resistancewas investigated in an additional set of experiments by rotating the cast bed through 180◦ inthe flume. The main focus of the paper is on the comparison of the bulk flow characteristics forthe three different cases for which the beds are characterized not only by the same characteristicgrain-diameter but also by an identical surface structure. The obtained results show that theporous, non-porous bed and rotated bed result in different flow resistance and that both bedporosity and grain-orientation have a significant effect on flow resistance.

Keywords: Flow resistance, gravel, bed rivers, casting technique


205



Bedload transport and hydro-abrasive erosion at steep bedrockrivers and hydraulic structures

Michelle Muller-Hagmann ∗ 1, Christian Auel 2, Ismail Albayrak 1, Robert M. Boes † 3

1 Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich – Honggerbergring 26,8093, Zurich, Switzerland

2 ILF Consulting Engineers (ILF) – Feldkreuzstraße 3 6063 Rum bei Innsbruck, Austria3 Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich – Honggerbergring 26, 8093

Zurich, Switzerland

Sediment transport in glacier basins and rivers, and hence reservoir sedimentation tend toincrease under the impact of climate change. The raise of bedload transport rates results in anincrease of hydro-abrasive erosion leading to bedrock incision in rivers and wear at hydraulicstructures. Mechanistic abrasion models are a helpful tool for both river and landscape evolu-tion and hydroabrasion of hydraulic structures. Therefore, knowledge of the physical processesof turbulent flow characteristics, bedload particle motion, and hydroabrasion and their inter-relations is needed. Ongoing research at VAW of ETH Zurich aims at improving the requiredknowledge to address hydroabrasion issues by means of laboratory and prototype experimentsin supercritical flows over fixed smooth and transitionally rough beds. A physical model inves-tigation revealed that particle trajectories on fixed planar beds are rather symmetric, flat andlong compared to alluvial beds. By applying newly developed particle motion equations, anexisting mechanistic abrasion model was adapted and calibrated for concrete and natural rockby means of prototype data. This advances abrasion prediction modelling and contributes toa better understanding of river bed and landscape evolution and to a sustainable design andoperation of hydraulic structures facing severe hydro-abrasive erosion.

Keywords: abrasion model, bedload transport, bedrock river incision, hydroabrasion, supercritical

flow, sediment bypass tunnel, steep bedrock river


206



Effect of aspect ratio on higher order moments of velocityfluctuations in a rough open channel flow experiment

Minakshee Mahananda ∗† 1, Prashanth R. Hanmaiahgari 1

1 Department of Civil Engineering, IIT Kharagpur, Kharagpur-721302 – India

The effect of aspect ratio on the higher order statistics of velocity fluctuations in a hy-draulically rough turbulent open channel flow is investigated. In this regard, an experiment wasconducted in a rough bed narrow open channel flow of aspect ratio equal to three and the instan-taneous flow velocities were measured using a Nortek Vectrino+ Acoustic Doppler Velocimeter.To understand the effect of aspect ratio, the results obtained from the present experiment arecompared with the literature data of approximately same Reynolds number and bed roughnessin a wide open channel flow for turbulence intensities and higher order statistics of velocity fluc-tuations. The experimental results show that third order moments of velocity fluctuations aresensitive to aspect ratio in the outer region. Turbulence intensities comparison between NarrowOCF and Wide OCF shows higher streamwise and vertical turbulence intensities in the outerregion in Narrow OCF.

Keywords: Secondary currents, Narrow open channel flow, Turbulence, Aspect ratio, Hydraulically

rough flow, Hydraulically smooth flow.


207



Reducing Darcy coefficient by using drag reduction methods inopen-channel flows: effect on discharge capacity and potential

application to mitigate river flooding impact

Emmanuel Mignot ∗† 1, Nicolas Riviere 1, Arnaud Lefevre 2, Bernard Quillien 2

1 Laboratoire de Mecanique des Fluides et d’Acoustique (LMFA) – CNRS : UMR5509, Univ. C.Bernard - Lyon I, Ecole Centrale de Lyon, INSA – 36 Av Guy de Collongue 69134 Ecully Cedex –France

2 SNF SAS – Rue Adrienne Bolland, ZAC de Milieux, 42163 Andrezieux Cedex – France

Discovered by Toms in 1948, the drag reduction method by polymer additives is a commonstrategy used to minimize friction losses when carrying fluids (water, oil, slurries) in pipes overlong distances. It allows to dramatically reduce the wall friction and thus to reduce the linearhead losses by up to 80%. The origin of this phenomenon lies in the interactions between theturbulent structures of the flow and the polymer macromolecules added to the fluid. Oppositely,the use of such additives in open-channels has remained until now very scarce. The aim of thepresent project is to evaluate the gain in discharge capacity - or loss in water depth for a givendischarge - of an open-channel flow in idealized laboratory conditions. For this purpose, threetypical straight open-channel flow configurations, are tested herein without and with added dragreducer polymers of different concentrations: i) gradually varied flows over a smooth bed forwhich backwater curves and vertical profiles of velocity are measured to investigate the effect ofthe polymer on the boundary layer velocity profile, ii) gradually varied flows above a rough gravelbed to check if a rough boundary layer is also affected by the drag reduction process, and iii) flowswithin a channel with fixed impervious emerging cylinders to investigate the effect of polymers ina flow which resistance is governed by the drag forces applied by emerging obstacles. The resultsof the three series of experiments then permit to conclude on the potentiality of added polymersto reduce the flow resistance in open-channel flows. For instance, a concentration of 20ppm ofdrag reducer polymers leads to decrease the normal water depth by about 20% in a smoothstraight open-channel. A discussion is finally proposed regarding the possible application ofsuch polymers to open-channel geophysical and industrial flows, such as mitigating the 100-yearflood impact of a river.

Keywords: Friction coefficient, Polymers, Drag reduction, Experiments, Open, channel


208


Friday 7 September, 14:00 – 15:40 Me 9 – Bank erosion

Wave erosion of cohesive and non-cohesive embankments:laboratory experiments

Yavuz Ozeren ∗† 1, Daniel Wren 2

1 National Center for Computational Hydroscience and Engineering, the University of Mississippi(NCCHE) – 327 Brevard Hall, University, MS 38677 – United States

2 USDA-ARS National Sedimentation Laboratory – 598 McElroy Drive, Oxford, MS 38655 – UnitedStates

Laboratory experiments were carried out in a wave tank to investigate wave induced beachprofile evolution and scarp recession on cohesive and non-cohesive model embankments. Thecohesive embankment was constructed using a natural soil mixture, and the non-cohesive em-bankment was constructed using cylindrical shaped polyethylene terephthalate (PET) pellets ofuniform size. A standardized packing procedure was used for both cohesive and non-cohesiveembankments. The onshore face slope of the embankment was approximately 30 degrees. Themorphological evolution of the embankment was monitored using water level sensors and a time-lapse camera. Waves quickly eroded the bank face near the free surface and formed a scarp.While an equilibrium profile was established relatively quickly and at a much steeper slope forthe non-cohesive embankment, the cohesive embankment continued to erode for a much longerperiod. The scarp of the cohesive embankment retreated by a series of wave undercutting andslump failures. An empirical relationship between incident wave height and embankment erosionwas established for the tested conditions. The measured beach profiles were compared with thedeveloped analytical solution.

Keywords: Bank erosion, wave erosion, scarp retreat


209



Impact Analysis of Sand Dredging from Alluvial Tidal River

Md Kabirul Islam ∗ 1, Numan Al Kibriya † 1, Md. Maruf Dustegir 2

1 Dept of Environmental, Water Resources and Coastal Engineering (EWCE), Military Institute ofScience and Technology (MIST) – Mirpur Cantonment, Dhaka-1216 – Bangladesh

2 Institute of Water and Flood Management (IWFM), Bangladesh University of Engineering andTechnology (BUET) – Dhaka – Bangladesh

The Government of Bangladesh has planned to make a large build up area (BUA) in a newlydeveloped sedimentary point bar (locally known as ‘Char’) at Lebukhali along the northernbank of Payra river in the southern part of the country. From a study it was revealed that,this sedimentary bar has to be raised by 3.45 meter from MSL to keep it free from any extremeevents (like tidal and storm surge effects) for 100 years return period. Accordingly, it hasbeen planned to collect the required filling material (estimated 57.6 million m3 of sand/soil)by dredging the same river bed. In Bangladesh dredging of river is very popular and widelyundertaken to collect filling and construction materials, but its adverse impact on river bed,bank and adjacent areas are hardly probed. This study aimed at analyzing the adverse impactsof dredging from Payra River bed. Four alternative sand bars were identified as dredging areaat varying distances located both upstream and downstream of the proposed site. The dredgingimpacts were analyzed for different boundary conditions. The study is based on physical survey(topographic and bathymetric surveys), historical data and numerical model analysis. Numericalmodel was applied through Delf 3D to investigate the impact on flow parameters: flood depthand velocity magnitude. Continuous field visit and observations were made through last oneyear to observe real impact. The analysis revealed that dredging of any of the bars have resultedchanges in flow field. The distance of dredging point does not control the flow field rather thedredging volume, depth and upstream condition determine the effects on bank erosion. As such,the dredging locations have beenprioritized considering the least possible effects on river bankerosion and founded that little erosion is taking place for both upstream and downstream region.However, the long term impacts in other areas of the river need to be investigated as the timepass.

Keywords: Buildup Area, Sandbar (Char), Dredging, Flood depth, Bank line shift


210



Numerical Simulation of lateral dike breaching due toovertopping

Benjamin Dewals ∗ 1, Ismail Rifai 1,2, Kamal El kadi Abderrezzak 2, Massimo Greco † 3,Cristiana di Cristo 4, Michele Iervolino 5, Angelo Leopardi 4, Andrea Vacca 3

1 Hydraulics in Environmental and Civil Engineering, Research unit Urban & EnvironmentalEngineering, University of Liege (ULg) (HECE) – Belgium

2 Laboratoire dHydraulique Saint-Venant – 6 quai Watier, BP49, 78401 Chatou Cedex – France3 DICEA, University of Naples ”Federico II” – Italy

4 DICeM, University of Cassino and Southern Lazio – via G. Di Biasio, 43 - 03043 Cassino (FR), Italy5 Dipartimento di Ingegneria Civile, Design, Edilizia e Ambiente - Universita della Campania ”Luigi

Vanvitelli” – Aversa (CE) – Italy

Dikes and levees are encountered very often along rivers. They are crucial as defence struc-tures for flow channelization, protecting population and properties from floods as well as againstlateral riverbed migration. However, the combination of their aging and increased expositionto extreme hydrological events may cause these structures to breach, and subsequently to fail.Understanding the dynamics of breaching is very important for developing adequate counter-measures, for civil protection initiatives and for land use planning.Recent literature shows many studies concerning, both from experimental and numerical pointof views, frontal dike breaching (eg Schmoker and Hager, 2012). Based on several evidences, itis well assessed that depth-integrated numerical models can successfully reproduce this kind ofphenomenon (e.g. Greco et al., 2012).Recently, Rifai et al. (2017) investigated a different setup in which the embankment is parallelto the main channel flow and thus a lateral breaching occurs. It is worth of noting this schemeresembles real-world situation of levees breaching along a river.In present paper, the capability of depth-integrated approaches in reproducing such tests is in-vestigated. Numerical results obtained with different models are compared against experimentsfrom both the qualitative and quantitative point of views. Considerations about the applicabil-ity of depth-integrated models in real world situation of lateral breaching of dikes and levees arealso drawn.

Keywords: sediment transport, dyke breaching, numerical models, geofailure


211



Numerical modelling of cantilever failure and effect of slumpblocks on meander migration

Kattia-Rubi Arnez-Ferrel ∗ 1, Ichiro Kimura † 2, Yasuyuki Shimizu 1

1 Graduate School of Engineering, Hokkaido University – Japan2 University of Toyama – Japan

Many countries around the world are affected more or less by bank erosion. Riverbank erosionis considered to be unpredictable and has severe social, economic and environmental impact.As a result of bank migration, the loss of soil eventually will threat structures established nearriverbanks and human lives. In this study we focused in cantilever failure which is characterizedfor the development of an overhanging part as a result of fluvial erosion in banks with cohesivematerial. The overhanging part eventually will fall into the water and it will remain in fronton the bank until erosion occur again. This material called ”slump blocks” mostly will protectthe bank and then the migration rates will decrease. The objective of this paper is to developa numerical model to study the effect of slump blocks in the meander river migration.Given the large temporal and spatial scale in rivers, we considered that the best approach forthis problem was to develop a numerical model. Although there are good models for modellingbank erosion, not many include the effect of slump blocks and almost none has developed aphysical description of the phenomenon.The methodology consists in combining two numerical models: Patsinghasanee et al and Garciaet al. The first model described physically the different mechanisms of cantilever failure and theeffect of slump blocks in cohesive banks. However, the model was limited to a straight channeland the velocity profile was only dependant on the depth.The second one, consisted in a simple but interesting approach based on Ikeda et al’s model whichrelates the bank erosion rate to be proportional to the near-bank velocity. Nevertheless authorsconcluded that it was necessary to improve the bank erosion module to compute migration rates.As bank erosion is most likely to occur in the outer bank river bend the first problem was toimprove Patsinghasanee et al’ s model from a straight to a curved channel, this means, includingthe curvature effect. Then the velocity profile was corrected by the effect of curvature usingGarcia et al’s mathematical solution. Furthermore we considered the effect of the secondarycurrent of the first kind on the sediment transport.In order to consider the curvature of a meander, we modified Patsinghasanee et al model by usingtheir near-bank velocity model and including the effect of secondary flow. Once we coupled theprograms, numerical simulations were performed using a channel with cohesive material. Theresults then, were compared with results of the literature to validate the capacities of the model.In conclusion, the model was able to represent the mechanisms of cantilever failure with slumpblocks and the effect of slump blocks in meander migration patterns. The work helps to betterunderstand the cantilever failure mechanisms in river with cohesive banks.

Keywords: slump blocks, bank erosion, cantilever failure, cohesive banks


212



River bank erosion opposite to transverse groynes

Alessandra Crosato ∗† 1,2, Jose Bonilla Porras 1, Arthur Pinkse 2, Tsegaye Tiga 1

1 IHE Delft Institute for Water Education (IHE Delft) – Westvest 7, Delft – The Netherlands2 Delft University of Technology (TU Delft) – The Netherlands

Long series of groynes are built from both river sides to narrow river channels and preventbank erosion, which results in fixed channel alignments. Also single or short series of groynesare built, in particular to prevent local erosion, deviate the water flow, free an intake or fixthe position of migrating bars at certain locations. These structures divert the flow towardsthe opposite river side where bed scouring increases the risk of bank failure. Flow and bedadaptation have been extensively studied, especially for long series of groynes. Instead, studiesdealing with opposite bank erosion caused by single or short series of groynes are still lacking.We investigated this phenomenon in the laboratory and using a 2D numerical model.We analysed the evolution of a straight channel excavated in a sandy bed, in which a single groyneor three groynes in a series were placed transversally to the flow from one bank. We consideredtwo groyne lengths and three distinct cases characterized by different constant flows but identicalsediment input rates. A total of 14 experimental tests were carried out in the Laboratory ofFluid Mechanics of the Delft University of Technology. Starting with a horizontal bed, wemonitored the evolution of bank alignment and bed topography until a state of morphodynamicequilibrium, characterized by constant longitudinal slope and sediment output, was reached.Poorly graded sand having median diameter of 1 mm produced vertical banks that retreatedthrough sequences of failures. As expected, bank erosion occurred at the side opposite to thegroyne, but downstream of the structure and it appeared to be related to the formation of a largebar rather than to the groyne itself. The location of maximum bank retreat was situated at adistance from the narrowed cross-section that scaled with the transverse flow adaptation length(1-3 times the undisturbed channel width). Surprisingly, at the lowest flow shorter groynesproduced more bank erosion. To analyse this we used a 2D numerical model constructed withthe Delft3D software including Large Horizontal Eddy Simulations, which was calibrated on flowvelocity measurements.In general, the results of this study show how bank accretion may induce opposite bank erosion,since the construction of a single transverse groyne can be regarded as point bank advance.Particularly important for opposite bank erosion is the development of alternate or central barsin the river channel, which depends on eddy formation downstream of the groyne and on localchannel widening. An important result for river engineers is related to the bank protectionworks that are needed at the river side opposite to a groyne. The results of this study indicatethat the length of the bank that should be protected scales with the length of the bar that formsdownstream of the groyne. In addition, the study shows that the area that is most susceptibleto bank erosion is downstream of the groyne and not directly opposite to it.

Keywords: river groynes, bank erosion, mobile bed, laboratory experiments


213


Friday 7 September, 14:00 – 15:40 Li 9 – Bedload and bed evolution modelling

Bedload transport modelling using kinetic theory

Vaclav Matousek ∗† 1, Stepan Zrostlik 1

1 Czech Technical University in Prague – Czech Republic

Intense transport of bed load is associated with high-concentrated sediment-laden flow overa plane mobile bed at high bed shear. Typically, the flow exhibits a layered internal structurein which a vast majority of sediment grains is transported through a collisional layer above thebed. Our investigation focuses on steady uniform open-channel flow with a developed collisionaltransport layer and combines modelling and experiment to relate integral quantities, as thedischarge of solids, discharge of mixture, and flow depth with the longitudinal slope of thebed and the internal structure of the flow above the bed. In the paper, flow with the internalstructure described by linear vertical distributions of granular velocity and concentration acrossthe collisional layer is analyzed by a model based on the classical kinetic theory of granularflows. The model predicts the total discharge, the discharge of sediment, and the flow depth forgiven (experimentally determined) bed slope and thickness of collisional layer. The model alsopredicts whether the intefacial dense layer develops between the bed and the collisional layerand how thick it is. Model predictions are compared with results of intense bed-load experimentcarried out for lightweight sediment in our laboratory tilting flume.

Keywords: sediment transport, intense bed load, grain collisions, tilting flume experiment


214



Lagrangian modeling of bedload movement via the impulseentrainment method

Micah Wyssmann ∗ 1,2, Thanos Papanicolaou † 1,2

1 Hydraulics and Sedimentation Laboratory (HSL) – 2021 Stephenson Drive, Knoxville, TN 37916-4514– United States

2 Department of Civil and Environmental Engineering, University of Tennessee – 325 John D. TickleBuilding, 851 Neyland Dr., Knoxville, TN 37996-2313 – United States

At low shear stresses merely above incipient conditions, the characteristic travel patterns ofbedload particles remain difficult to predict due to intermittent movement. At these conditions,particles rest, are entrained into the flow when sufficient momentum transfer from near-bedturbulence occurs, and then come to rest again. The overarching goal of this research is to closethe critical gaps related to intermittent movement in order to allow for Lagrangian modeling ofbedload at near incipient conditions. Thereby, the specific objectives of the present work areto predict the statistics of (1) the particle resting time, tR, and (2) the magnitude of hydrody-namic momentum transfer (or impulse) during entrainment, Ient. To predict these statistics, weemployed the conceptual framework of the impulse entrainment method and predicted impulsestatistics by simulating turbulent time series realizations with a generic, regime-based stream-wise velocity spectrum. Model validation was carried out by directly comparing simulationresults with published experimental impulse and particle entrainment statistics. Model predic-tions showed that an increase in stress was correlated with a sharp decrease in the average tRand an increase in Ient.

Keywords: particle entrainment, impulse model, resting time, lagrangian modeling


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A well-posed model for mixed-sediment river morphodynamics

Victor Chavarrias ∗† 1, Guglielmo Stecca 2, Robert-Jan Labeur 1, Astrid Blom 1

1 Delft University of Technology (TU Delft) – PO Box 5048 2600 GA Delft – The Netherlands2 National Institute of Water and Atmospheric Research (NIWA) – New Zealand

To predict changes in bed elevation due to currents, commonly a hydrodynamic model thataccounts for the flow of water (i.e., the Navier-Stokes equations or a simplification of them) issolved in combination with a morphodynamic model that accounts for the mass conservationof bed sediment. The Exner equation represents the mass balance of the total amount of bedsediment. Hirano developed the active layer model to account for mixed-size sediment processes(downstream fining in rivers, bed surface armoring, or bend sorting). This equation representsthe mass conservation of each sediment size fraction. In his model, only the top part of the bed(i.e., the active layer) is assumed to interact with the flow. That is, sediment is eroded fromand deposited in the active layer and the sediment transport rate depends on the grain sizedistribution of the active layer. The sediment in the active layer is considered to be mixed so itdoes not have vertical stratification. The substrate sediment does not directly interact with theflow and it can have vertical stratification. Sediment from the active layer is transferred to thesubstrate if aggradation occurs and sediment from the top part of the substrate is mixed withthe one in the active layer in case of degradation. The system of equations is usually closed witha deterministic relation that links the local bed shear stress with the sediment transport.This framework has proven its validity for almost half a century of research and engineering.However, we find two main problems, one related to the sediment transport and the second tothe mixing processes. The Exner equation in combination with a local and deterministic closurerelation for the sediment transport rate does not account for processes such as the variabilityin the sediment transport rate, diffusion, and adaptation to capacity load. As regards to thesecond problem, the active layer model neglects some physical processes which are relevant undercertain circumstances. For example, it does not account for sediment mixing due to bedforms.Moreover, the active layer model can be mathematically ill-posed which implies that infinitesimalperturbations in the initial or boundary conditions produce significant changes in the solution,which results in the model losing its predictive capability.First we modify the active layer model to guarantee that it is always well-posed. To this end weintroduce a parameter that modifies the celerity at which sorting processes occur. We comparethe results to laboratory experiments conducted under conditions in which the active layer modelis ill-posed. We find that the modified model captures the mean evolution but not the short timescales. To capture the small time scales we develop a model that includes the physics relatedto the above mentioned first problem. To this end we consider an existing model that accountsfor the exchange of particles between the bed and the bedload layer. The model originatesfrom a stochastic interpretation of sediment transport and captures the diffusive and adaptationdynamics. We extend this model to account for mixed-size sediment and combine it with anadapted active layer model based on an entrainment and deposition formulation. Preliminaryresults show that the new model is well-posed and that, under the conditions in which the activelayer model is ill-posed, the new model presents an instability mechanism such that waves of acharacteristic length are amplified, causing mixing of the sediment as observed in the laboratoryexperiments. We present the results of a second set of laboratory experiments conducted underconditions that allow for the full formation of the waves predicted by the new model.


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Keywords: active layer, preconditioning methods, stochastic sediment transport, instability mech-

anism

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A simple non-equilibrium bedload transport equation for theformation of dune in a shallow-water flow over an erodible bed

Pablo Canada-Pereira ∗ 1, Patricio Bohorquez † 1,2

1 Area de Mecanica de Fluidos, Departamento de Ingenierıa Mecanica y Minera, Universidad de Jaen –Campus de las Lagunillas, 23071 Jaen – Spain

2 Centro de Estudios Avanzados en Ciencias de la Tierra (CEACTierra), University of Jaen –Campusde las Lagunillas, 23071 Jaen, Spain

In this work, we consider the long-standing problem of capturing dune formation in anerodible-bed channel at subcritical speed by using a reduced order model of depth-averagedequations. The pioneering study by Reynolds (J. Fluid Mech., 22:113-133, 1965) showed that thestandard Saint-Venant-Exner equations are unconditionally stable at subcritical Froude number.Hence, the use of depth-averaged flow equations, which are commonly used by the hydrauliccommunity, prevent the formation of bedforms as dune. Recently, Canada-Pereira & Bohorquez(J. Fluid Mech., revised, 2018) have proposed a simple sediment transport formulation able tocapture the formation of dune when coupled with the Saint-Venant equations. We replace thestandard Exner equation with a non-equilibrium sediment transport equation that includes thefollowing necessary ingredients: first, a phase shift in the particle entrainment rate; second, aparticle diffusivity and an eddy viscosity. Subsequently, we solve the linear stability problem ofan erodible-bed channel and show that the neutral curve properly captures the bed instabilityboth in subcritical regime (i.e. dune) and supercritical flow (i.e. antidune and roll wave). Finally,we corroborate the capabilities of the model by means of non-linear numerical simulations whichreproduce the growth of dune and antidune in agreement with experiments.

Keywords: Dune, Antidune, Roll wave, Bedload, Exner equation, Linear stability analysis


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Stochastic bedload transport in mountain streams: models

Christophe Ancey ∗ 1, Patricio Bohorquez † 2

1 Ecole Polytechnique Federale de Lausanne – Station 18, 1015 Lausanne, Switzerland2 University of Jaen – Spain

Describing bedload transport as a stochastic process is an idea that emerged in the 1930swith the pioneering work of Einstein. For a long time, the stochastic approach attracted marginalattention, but the situation has radically changed over the last decade with the recent advancesin the theory of bedload transport. In parallel, the implementation of bedload monitoring tech-niques at high temporal resolution has produced a wealth of interesting results showing, amongother things, that classic empirical bedload transport equations do not capture neither the meanbehavior of sediment transport rates Qs nor its order of magnitude, especially at low sedimenttransport rates (a case that is most frequent in mountain streams).We have developed a stochastic model that takes inspiration from population dynamics. Thebuilding block is an Eulerian description of the number N of moving particles in a fixed vol-ume. An evolution equation for N (master equation) can be derived using the framework ofbirth death Markov process (Ancey, J. Geophys. Res., 115: F00A11, 2010). By generalizingthis equation to an array of adjacent volumes, we end up with a stochastic formulation of themass balance equation for the bedload (Ancey & Heyman, J. Fluid. Mech., 744: 129, 2014).The number of moving particles per unit streambed area is called “particle activity” γ. In ourapproach, γ is a random variable, which varies with time as a result of entrainment, deposition,and transport. Under steady state conditions, the model is able to capture the salient featuresof sediment transport (i.e., the probability distribution function of transport rate, its autocor-relation time). An ensemble-averaged equation can also be derived for particle activity (thisequation takes the form of a nonlinear advection diffusion equation with a source term).There is a strong coupling between transported sediment, bed morphology, and flow conditions,which can be described using the shallow water equations supplemented by the stochastic massbalance equation (that can be considered a stochastic Exner equation). We refer to the result-ing system of equations as the Saint-Venant-Exner (SVE) equations (Bohorquez & Ancey, Adv.Water Resour., 83: 36, 2015; Appl. Math. Model., 40: 7474, 2016).Three theoretical or numerical problems have been studied to understand how the input parame-ters of the model affect the model outputs: (i) the derivation of the stochastic evolution equationfor the number of moving particles over fixed plane beds, which leads to exact analytical solu-tions of the particle activity fluctuation; (ii) the nonlinear simulation of the ensemble-averagedSVE, which successfully captures the anti-dune regime observed experimentally; (iii) the non-linear simulation of the stochastic SVE, which is considered a major challenge.For the moment, the model holds promise for predicting bed morphology and transport ratesunder various flow conditions provided that sediment transport is not too intense (in that case,multiple events occur, e.g. correlated particle motions, and the stochastic model breaks down).A remarkable achievement has been the proof that the SVE equations are absolutely unstableand lead to bedform form formation and migration as soon as the Shields number exceeds athreshold. In other models, this result can be achieved only by significantly affecting the struc-ture of the governing equations or employing ad hoc assumptions.We are currently working on the integration of various processes involved in bedload transport(two-dimensional flow, grain sorting and hyporheic flows) to overcome the model limitations.


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Keywords: Exner equation, shallow, water equations, stochastic model for bedload transport, sta-

bility analysis, bedform, numerical scheme

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Velocity profile and depth-averaged to surface velocity innatural streams: a review over a large sample of rivers

Alexandre Hauet ∗† 1, Thomas Morlot 1, Lea Daubagnan 1

1 EDF - Division Technique Generale (DTG) – 21 rue de l’Europe - 38040 Grenoble Cedex, France

The knowledge of the discharge of river during extreme flood is of prime importance for thescientific and the research community, for applications such as the sizing of hydraulic structures,risk management or simply for the understanding of the hydrology of such events. Unfortunately,measuring discharge using conventional methods, such as current meter or ADCP, is impossiblebecause the high velocities and the floating debris endanger the operators and the equipment.More, extreme floods are highly unsteady and discharge can vary drastically in a very shorttime, especially during flash flood. The typical time-scale for gauging (time of displacementof the gauging teams and time of measurement itself) does not match up to the time scale ofthe dynamic of extreme flood. Recently, non intrusive method for measuring discharge havebeen developed and tested in flood conditions. Doppler surface velocity radar (SVR) and imageanalysis like Large Scale Particle Image Velocimetry (LSPIV) or Space Time Image Velocimetry(STIV) showed their efficiency for measuring surface velocity during extreme events. In orderto compute discharge with non intrusive methods, the shape of the vertical distribution of thevelocity and of the coefficient relating depth-averaged velocity to surface velocity (called Alpha)must be known. Abundant literature exists on the theory of velocity profile in rivers, but areview of in situ measurements over a large sample of rivers was missing.In this paper, 3611 discharge measurements realized by Electricity of France (EDF-DTG) witha current meter are used to compute vertical distribution of velocity and the coefficient Alpha.The gaugings were realized at 177 different sites, located close to EDF-DTG’s hydrometricstations. The measurements cover a very large range of discharges (0.01 to 863 m3/s), river sizes(width ranges from 0.5 to 90 m, hydraulic radius ranges from 0.05 to 5.36 m) and morphologies(from mountain rivers with gravel bed to sandy plain rivers and concrete channels). At EDF-DTG, gauging are always realized with an important number of velocity measurement pointsper vertical (at least 5) and with the measurement of the velocity as close to the free surfaceas possible systematically. For each gauging verticals realized close to the river banks areremoved, to avoid edges effects. Then, measurements’ depth and velocity are normalized (withthe vertical’s depth and averaged velocity respectively) and three different methods are used tocompute a for a gauging : (method 1) the average of the normalized velocities measured close tothe free surface equals 1/Alpha; (method 2) a log-law is fitted over the normalized measurementswith a statistical adjustment of the hydraulic roughness; (method 3) a power-law is fitted overthe normalized measurements with a statistical adjustment of the hydraulic roughness and thebed-shear velocity. Methods 2 and 3 are applied if the measurements follow a log or power lawrespectively, using a statistical t-test.Over the 3611 gaugings, the averaged value of Alpha is about 0.8, with few differences betweenthe method used (0.83 for method 1; 0.81 for method 2; 0.79 for method 3). The standarddeviation is small (about 10%) for all the tested methods. With method 1, Alpha ranges from0.3 to 2.3. The extreme values are associated to specific gauging conditions, like wind effect,backwater effect due to a weir, or aquatic vegetation effect (inflection). The paper shows thatAlpha increases with the hydraulic radius (from 0.8 for Rh < 1 to 0.87 for Rh > 3), andslowly decreases with the width-to-depth ratio. Alpha is also linked to the bed roughness,evolving from 0.85 for the concrete channels to 0.79 for gravel beds.The paper describes the


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measurement dataset, the methods used for the computation of Alpha, and gives analysis of thebehavior of Alpha regarding some physical parameters.

Keywords: Gauging, discharge measurement, non intrusive methods, velocity profile

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The estimation of the uncertainty associated with rating curvesof the river Ivinhema in the state of Parana, Brazil

Luiz Maldonado ∗ 1, Daniel Kazay † 1, Elio Romero 2

1 Itaipu Binacional – Brazil2 Itaipu Binacional – Paraguay

The estimation of the uncertainty associated with stage-discharge relations is a challenge tothe hydrologists. Bayesian inference with likelihood estimator is a promissory approach. Thechoice of the likelihood function has an important impact on the capability of the model torepresent the residues. This paper aims evaluate two likelihood functions with DREAM algo-rithm to estimate specific non-unique stage-discharge rating curves: normal likelihood functionand Laplace likelihood function. The result of BaRatin is also discussed. The MCMC of theDREAM and the BaRatin algorithm have been compared and its results seem consistent for thestudied case. The Laplace likelihood function presented as good results as normal likelihoodfunction for the residues. Other gauging stations should be evaluated to attend more generalconclusions.

Keywords: Bayesian inference, uncertainty, rating curves


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Monitoring and analysis of lowland river discharge

Ton Hoitink ∗† 1

1 Wageningen University (WUR) – Netherlands

In single-thread channels with a sloping bed and quasi-steady conditions, river discharge canoften directly be inferred from the water level using a rating curve. Challenges occur when thebed slope becomes negligibly small, or when the discharge becomes highly dynamic such as inthe case of tides. This paper discusses recent work on monitoring and analysis of river dischargedynamics under such complicating circumstances. In lowland rivers, backwater has an effect onwater levels that extends over a large region for smaller bed slopes. Results from a rainfall-runoffmodel and discharge measurements in the Mahakam catchment show that when a rating curveis developed in a backwater effected river, it essentially filters the backwater effects out of thedischarge series. In coastal lowland plains, marine impacts cannot be ignored. Tidal wavesmay propagate hundreds of kilometers inland and interact with the river discharge. AcousticDoppler current profilers are increasingly being employed for discharge monitoring in lowlandrivers. A recently developed error model shows that the acoustic range needs to extend beyondthe distance from the river bank where the depth mean flow velocity exceeds the cross-sectionaveraged velocity.

Keywords: discharge monitoring, rating curves, tidal rivers, discharge in estuaries, backwater effects


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Measurement of inundation flow from a broken embankment byusing video images shot from a media helicopter

Ichiro Fujita ∗† 1, Yuichi Notoya 2, Takanori Furuta 3

1 Kobe University – 1-1 Rokkodai-cho, Nada-ku, Kobe, 657-8501 – Japan2 CTI Engineering, Co., Ltd. – Japan

3 Graduate School of Engineering, Kobe University – Japan

In the event of a disaster, the situation of the disaster is videotaped from the air and isoften broadcasted by media helicopter. Or, images taken from UAV by residents are sometimesuploaded to the web site to show the actual situation of the disaster. In particular, the pointto note when targeting water disasters such as flood, inundation flow, and debris flow is thatairborne video images showing disaster situations are captured from a wide range of perspectives.It is significant that disaster situation is obtained not with photographs but with movies becauseit can convey the misery of disasters more accurately and at the same time it could be possibleto extract quantiative information of the flow from those video images.In this paper, an image analysis system for measuring water surface flows was developed that cantreat airborne video images in which the shooting angle varies from time to time. The target ofthe actual disaster was shoot from a media helicopter during the inundation disaster that ocurredon September 10, 2015 in the Kinugawa River in Japan. The disaster stemmed from the factthat the linear precipitation band remained in the same place for a long time and part of theembankment broke down during the flood, causing inundation over a wide residential area. Sincethe embankment crash occurred during the daytime, the flooding situation was clearly observedby a media helicopter and broadcasted. In this research, five DVDs were provided by the JapanBroadcasting Corporation that records three and a half hour video of the disaster, including theoverflowing flow from the broken part of the embankment, wooden houses being destroyed by theflow, and spreading of inundated flows. In the analysis, surface flow velocities were analyzed byapplying the image-based techniques such as the large-scale particle image velocimetry (LSPIV)or the space-time image velocimetry (STIV). Prior to applying the imaging techniques, theobliquely viewed continuous images were stabilized by utilizing the marker tracking method totrack the apparent background movement. Next, the stabilized images were orthorectified byadjusting the camera parameters so that the CG image generated using the detailed laser profiler(LP) data coincides with the original image. With the orthorectified images, the time change ofdischarge entering from the broken enbankment to the residential area and the total inundatedwater volume during the disaster were estimated. The inundated water volume estimated as1.10x107m3 in the present analysis roughly agrees with the officially reported data. In addition,the flow velocity distribution of the flooded stream flowing on the road and between the houseswere obtained by using LSPIV. The video provided by the media was compressed in size probablydue to the copyright relationship, and since the telop was inserted in the screen, the image qualitywas not good, but with the image analysis system developed this time the inundated flow featurewas captured fairly well. The analyzed data can be used as the measurement data in developinga simulation model of inundation.

Keywords: inundation, airborne image analysis, STIV, LSPIV, bank erosion


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Estimating the long-term evolution of river bed levels usinghydrometric data

Jerome Le Coz ∗† 1, Graeme Smart 2, D. Murray Hicks 2, Valentin Mansanarez 3,Benjamin Renard 1, Benoıt Camenen 1, Michel Lang 1

1 Irstea centre de Lyon-Villeurbanne, UR RiverLy – 5 rue de la Doua, Villeurbanne – France2 NIWA – Christchurch, New Zealand

3 Stockholm University – Stockholm, Sweden

The multi-decadal evolution of the geometry of river beds is only rarely monitored, typicallywith topographic surveys (cross-sections, longitudinal talweg or water-surface profiles). Evenwhen such data exist, their analysis poses problems of spatial and temporal representativeness:even when cross-sections are surveyed at the same location, they may not be representative;talweg is mobile and not fully representative of the average bottom level; water-surface profilesare measured for different flows, etc. The long-term morphological evolution of river beds isthen difficult to quantify precisely.Luckily, the gaugings and rating curves accumulated over decades at hydrometric stations area valuable source of information on the evolution of river beds. A first use is to explore fortemporal change in the water stage corresponding to a fixed flow rate, for the series of ratingcurves available. The choice of the reference flow is important because it determines the natureof the morphological feature the evolution of which is monitored: for a low flow rate, the stagewill generally be determined by the width and height of a local cross-section, whereas for anintermediate flow it will be representative of the average level of the main channel. In addition,the stage for an overbank flow will also account for the level of the floodplain. The advantageover topographic surveys is that hydraulically meaningful parameters can be estimated.This paper introduces an original method that has been developed to estimate the parametersof the successive rating curves by Bayesian analysis in sequence. This work is a developmentof the BaRatin method available for the Bayesian estimation of unique stage-discharge ratingcurves. These parameters no longer depend on a reference flow to be fixed, but are linked to thevarious hydraulic controls identified: low-flow control riffle, main channel uniform flow control,floodway (bars), floodplain, etc. The dates of rating changes are taken from existing hydrometricrecords. The uncertainty interval of each parameter is estimated, assuming, however, that norating change has been ignored by the station manager. It is thus possible to clearly distinguishevolution of the reach of channel adjacent to stage recorder (e.g., a degrading bed) from that oflocal riffles and to evaluate whether the observed temporal changes are significant compared tothe estimation uncertainties. The method is illustrated with two unstable rivers in New Zealand,each subject to different natural or anthropogenic pressures.

Keywords: river, morphology, hydrometry, rating curve, uncertainty


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Poster session

Posters

Poster session on Wednesday 5 September, 16:40 – 18:30

Main hall

P.A – River morphodynamics and restoration . . . . . . . . . . . . . . 228

P.B – Hydraulic structures and their effects on bed, flow regime and

ecology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

P.C – Sediment and pollutant dynamics in rivers . . . . . . . . . . . . 262

P.D – Fluid Mechanics and sediment processes . . . . . . . . . . . . . 266

P.E – Extreme events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

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Poster session P.A – River morphodynamics and restoration

Experimental investigation of low-angle dune morphodynamics

Suleyman Naqshband ∗† 1, Bas Wullems 1, Timo De Ruijsscher 1, Ton Hoitink 1

1 Wageningen University & Research (WUR) – The Netherlands

Dunes commonly dominate the bed of sandy rivers and they are of central importance inpredicting flow resistance and water levels. In the present study, we show that by using light-weight polystyrene particles as substrate in a laboratory setting, promising morphodynamicsimilarity is obtained between dunes in shallow flow (flume) and deep flow (field) conditions. Inparticular, results from our flume experiments show that dune lee-side angles, which are crucial inturbulence production and energy dissipation, better approximate dune lee-side angles observedin natural channels. Furthermore, dune height evolution towards upper stage plane bed observedin the present experimental study, closely follows dune height evolution as observed in world’slarge rivers.

Keywords: low angle dunes


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Validation of high-precision effects of a movable riverbedsimulation using unmanned aerial vehicles and structure from

motion

Masatsoshi Denda ∗† 1

1 Public Works Research Institute – Japan

For advanced and strategic management of gravel riverbed restoration and stopping of wood-land overgrowth, movable riverbed simulations and vegetation dynamic models that can describea ‘detailed riverbed materials’ transport’ influencing the vegetation dynamics and estimate thecreation area of a gravel riverbed are required. As first steps we verified the hypothesis whetherhigh-accuracy observation data using UAV and SfM improve the accuracy of water flow con-dition and movable riverbed simulation that can describe the riverbed materials’ transport indetail. In the results, High-precision river morphology using UAVs offers the ability to improvethe movable riverbed simulation. And these progresses indicated possibilities of UAV and SfMto develop vegetation dynamics model considering the riverbed materials’ transport.

Keywords: UAV, SfM, movable riverbed simulation, validation of high, precision effects


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Dune geometry estimation using apparent bedload velocity aspredictor variable

Gordon Gilja ∗† 1, Neven Kuspilic 1

1 University of Zagreb Faculty of Civil Engineering (UniZag) – Fra Andrije Kacica Miosica 26, 10000Zagreb – Croatia

Dune geometry is one of the most complex variables that influences flow pattern in openwatercourses. Dune formation rises scientific interest because it influences sediment transport,flow characteristics, bank erosion, flood control, navigation and the protection of land and in-frastructure. Research on dunes is mainly flume-based, and conclusions from such research arerarely, if at all, verified with field measurements. State of the art research is based on relationsbetween flow parameters and dune geometry, as well between dune geometry and migrationrate. Application of relations defined in flume conditions is limited due to stationary flow con-ditions and extrapolation issues for natural watercourses. Numerous researches have shownthat when bedload moves across dune covered rivedbed bedload transport rate is dependent ofdune migration rate and can be approximated from dune characteristics: cross-section geometryand migration rate. It is reasonable to assume that apparent bedload velocity has significantinfluence on dune field formation that has remained unexplored. Purpose of this research isto investigate applicability of apparent bedload velocity as argument in empirical relations fordune geometric characteristics. Apparent bedload velocity cannot be measured directly, there-fore method for its calculation from collected survey database was developed. This methodis implemented through algorithms and incorporated in software for data analysis during postprocessing. Survey data was collected on Drava river reach using hydroacoustic equipment forsimultaneous measurement of velocity profile and bathymetry data. Flow field characteristicsare defined through cross-sectional and stationary velocity profiles collected on independent sur-veys on control river cross-sections using Acoustic Doppler Current Profiler (ADCP). Dune fieldbathymetry was collected using Multibeam Echo Sounder (MBES). Hydroacoustic equipmentwas paired with RTK-GPS which enabled georeferencing and synchronization of collected datain plane coordinate system. Averaged flow parameters across river reach are calculated using1D numerical model calibrated for each survey. Aim of this thesis is implementation of apparentbedload velocity as argument in empirical relations for prediction of dune field characteristics. Inconventional empirical relations flow parameters are used to investigate relationship with dunelength, height and steepness. In this research apparent bedload velocity is used as argumentin regression analysis for dune geometry and results are compared with results from conven-tional empirical relations. Analysis is modelled on field survey dataset and numerical modelresults. Results were disseminated on individual profiles and coupled for river reach segments.These methods define comprehensive approach for description of dune field characteristics basedon collected velocity profile with ADCP. Implementation of this approach enables reliable andsimple acquiring of information of dune characteristics during hydrological monitoring.

Keywords: dunes, bedload, apparent bedload velocity, Acoustic Doppler Current Profiler, Multi-

beam Echo Souder


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Sediment management in tidal river: A case study of East BeelKhuksia, Bangladesh

Rocky Talchabhadel ∗† 1, Hajime Nakagawa 1, Kenji Kawaike 1

1 Disaster Prevention Research Institute, Kyoto University – Japan

The widespread construction of coastal embankments limited the natural deposition on thefloodplain and accelerated the silt deposition in river channels. It resulted in drainage conges-tion and large-scale waterlogging problem. The temporary de-poldering is one of the effectivemethods to solve this issue. During high tide, muddy water enters the selected tidal basin de-positing a major portion of sediment and at low tide, relatively clearer water erodes the riverbed.This paper presents a two-dimensional numerical model to simulate the mechanism of sedimenttransport and deposition during the process of controlled flooding. The model was applied tothree different scenarios of the embankment cuts in East beel Khuksia, Bangladesh. The studyrecommends operating single embankment cut at a time if the tidal equilibrium is fulfilled bythe opening size of that embankment cut. The developed model can be used to assess the landheightening in sediment-starved tidal basins and ultimately plan the rotation of tidal basins forsustainable sediment management.

Keywords: Tidal Basin Management, Beel, East Beel Khuksia, Embankment Cut, Tidal Basin


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Targeted water release to flush fine sediment out of bypassedsection of the Durance River downstream four dams

Remi Loire ∗† 1,2, Herve Piegay 1, Leah Beche 2, Quentin Dumoutier 3, Julie Mosseri 4

1 Environnement Ville Societe (EVS) UMR5600 – 18 rue Chevreul 69362 Lyon cedex 07 – France2 EDF CIH – 15 avenue Lac du Bourget, Savoie Technolac 73373 Bourget-du-Lac – France

3 SAGE Environnement – 12, Av. du Pre de Challes PAE des Glaisins 74940 Annecy – France4 EDF UP Mediterranee – 10 av. Vitton 13482 Marseille cedex 20 – France

Large-scale flow experiments are becoming more common as an increasing focus on improv-ing aquatic habitat quality and regulatory pressures incite dam operators to partially restorenatural flow regimes (Olden et al. 2014).Mediterranean rivers are characterized by their seasonal flow regime, with flooding in winterand spring and low base-flows during summer. In South-Eastern France, the Durance River,a Rhone River tributary, has a highly altered flow regime resulting from extensive hydropowerproduction and other water uses. Eight dams are present on the Durance, creating several by-passed reaches, with most of the water flowing into canals parallel to the bypass channel.Because of the naturally high fine sediment load in the Durance River (inputs from torrentialtributaries), unpredictable high flow events (dam overspill) are not always sufficient to reduceclogging, which has led to habitat degradation in bypassed reaches. Therefore, in addition to aregulatory increase in minimum flows, EDF is conducting a large-scale flow experiment, in thecontext of adaptive management, to test the efficacy of clear-water releases to restore benthichabitat conditions (reducing clogging) prior to spawning periods. Four reaches are targeted bythese releases, downstream of the following dams: Espinasses, La Saulce, l’Escale and Cadarache.The timing of these releases is defined for each dam based on the spawning period of target fishspecies.A comprehensive long-term monitoring program has been implemented (2014-2017). To monitorthe efficacy of releases, continuous measurements of water depth, TSS, turbidity, conductivity,temperature and dissolved oxygen are conducted during the release. Clogging (surface andinterstitial) is measured 15 days prior to the release, the day after the release and 1-monthpost-release. All measurements (continuous or punctual) are taken at 3 – 4 approximatelyequidistant stations. Surface clogging is evaluated visually using a semi-quantitative scale de-signed to describe the level of substrate embeddedness (Archambaud et al. 2005). Interstitialclogging is evaluated using a measure of hydraulic conductivity (Datry et al. In press). Particlesize distribution is evaluated using the Malavoi and Souchon (1989) method (a semi-quantitativeadaptation of the Wentworth scale). Substrate measurements are conducted at 30 points dis-tributed among 5-6 transects per station, placed such that they represent a succession of lotichabitats and correspond to potential fish spawning habitats. The presentation will focus on thismorphological aspects.Of the 16 programmed releases in the period, only 12 were undertaken. The 4 releases werecancelled because of two large flood event, a too high temperature and PCB pollution.Despite having placed the stations equidistant from each other, the propagation time for therelease differs substantially among stations: from 5 to 12 km/h, with little attenuation of thepeak flow over several kilometres, demonstrating that the pulse was hydraulically effective. Theminor changes observed in size distribution and morphology are likely due the influence of in-puts from torrential tributaries (localised rain events). The releases had a greater influence onfine sediment transport, which was observed as soon as the releases began. Suspended solid


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concentrations decreased rapidly despite a constant release flow. A mechanism of progressiveerosion was observed (the volume of mobilised sediments increased downstream). The releaseswere a success from a hydraulic perspective; future experiments will be conducted to determinewhether the release duration can be shortened and still obtain satisfactory results.Despite substantial fine-sediment transport, considerable surface clogging was still present atseveral stations post-release and clogging systematically increased between the second and thirdcampaigns. The study shows that erosions can be diffuse and that lentic areas provide sediments.Two other hypotheses can be formulated : an initial clogging too weak and a lack of precisionof the field measurements. Although turbidity measurements are often used as a criterion ofsuccess for water releases, the study shows that it is absolutely necessary to carry out fieldmeasurements on several stations. This experimentation shows that it is necessary to carry outthese types of operations in an adaptive management context. At this time, the results obtaineddo not lead to clear conclusions regarding their efficacy, mostly as a result of strong interannualvariation in hydroclimatic conditions, which have a strong influence on initial conditions andresulting outcomes.

Keywords: flushing flow, water release, sediment transport, river restoration, dam

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Analysis for Underwater Sound on Natural River Habitat

Jung-Eun Gu ∗† 1, Sang Hwa Jung 1, Joongu Kang 1, Hyoseop Woo 2

1 Korea Institute of Civil Engineering and Building Technology (KICT) – 283, Goyang-daero,Ilsanseo-gu, Goyang-si, Gyeonggi-do, 10223 – South Korea

2 Gwangju Institute of Science and Technology (GIST) – 123, Cheomdangwagi-ro, Buk-gu, Gwangju,61005– South Korea

A riffle-pool structure is a representative physical structure of bed in rivers. The changein the physical parameter of the habitat could lead to changes in the sound environment ofrivers, which are expressed by underwater acoustics. This change in underwater sound affectsfish habitat. In this study, the changes of underwater acoustics were analyzed according tothe change of pool-riffle sequence in a natural river. And the correlation between underwateracoustics and hydraulic characteristics was investigated. The survey for underwater acousticswas performed in the Namdae stream where is in Gangwon province. This stream belongs to theHan River basin and the river length is 39.01 km and the catchment area is 127.56 km2. TheNamdae stream is a river that accounts for more than 70% of salmon returning to South Korea.The spawning salmon will return to this area around November after growing in the BeringSea. It is important to manage the fish habitat in this river so there is a lot of research on theenhancement of fish habitat. Hydraulic characteristics were changed by the river bed structure.In this study, we investigated the relationship between underwater acoustic characteristics andhydraulic factors such as riverbed material, flow rate and water depth of each habitat type at 12sites. The characteristics of underwater acoustic differed relative to different hydraulic factorsof the two habitats, which is riffle and pool. The sound pressure level of riffles was relativelyhigher than that of the pools due to bed materials, shallow depth and high water velocity ofriffles. In the future, it is considered that the underwater sound can be utilized as a parameterto evaluate the physical habitat environment of the river.

Keywords: Underwater sound, Pool, Riffle, Fish habitat


234



Quantification of potential recruitment of large woody debris inmountain catchments considering the effects of vegetation on

hydraulic and geotechnical bank erosion and shallow landslides

Eric Gasser ∗† 1,2, Andrew Simon 3, Paolo Perona 4, Luuk Dorren 1,2, Johannes Hubl 2,Massimiliano Schwarz 1

1 Bern University of Applied Sciences (BFH) – Laenggasse 85, 3052 Zollikofen – Switzerland2 Univ. Natural Resources & Life Sciences (BOKU) – Jordan-Strasse 82, 1190 Vienna – Austria

3 Cardno – P.O. Box 1236, Oxford, 38655 Mississippi – United States4 The University of Edinburgh – Mayfield Road, Edinburgh EH9 3JL – United Kingdom

Large woody debris (LWD) exacerbates flood damages in the vicinity of infrastructure andin urbanized areas. The recruitment of ”fresh” large woody debris has been documented to bean key component of the total amount of wood transported during flood events in mountaincatchments. Predominately LWD recruitment due to hydraulic and geotechnical bank erosionand shallow landslides contribute to high volumes of wood during floods. Further, quantifyingthe effects of vegetation on channel and slope processes is extremely complex owing to differencesin species characteristics and has often been overgeneralized. To improve the quantification ofvegetation effects on LWD recruitment processes, a new model framework is being developedthat considers the effect of spatio-temporal distribution of root reinforcement and roughness onhydraulic and geotechnical bank erosion (BankforMAP) and shallow landslides (SlideforMAP)in mountain catchments. In this contribution we present the model framework as well as somepreliminary results.Hydraulic and geotechnical bank erosion resulting in potential LWD recruitment is modeledbased on hydraulic geometry relations (e.g. catchment size, channel slope, channel width, bankangle and height) and stream ordering to distinguish different recruitment scenarios based overa range of discharge scenarios (BankforMAP). In BankforMAP, material properties are calcu-lated applying BSTEM: A matrix of numerical experiments is set up to calculate importantprocesses-based parameters in order to represent a range of possible conditions in the channelnetwork. Flow and recruitment scenarios are based on the models key parameters (hydraulicgeometry relations, stream ordering and material properties). Potential LWD recruitment dueto shallow landslides is further modeled using SlideforMAP to generate shallow landslide andpotential LWD recruitment probabilities. SlideforMAP is a spatially explicit model that calcu-lates the probability of shallow landslides occurring on a slope considering root reinforcement.Spatial structures of forests as well as the position and tree dimensions are integrated in Bank-forMAP and SlideforMAP using the algorithm FINT for root reinforcement and potential LWDrecruitment modeling. Further, a probabilistic approach is being implemented to account for thespatio-temporal precipitation variability to estimate a LWD recruitment correction coefficient.The overlapping scenario-based results from BankforMAP and SlideforMAP allow us to gener-ate a probability matrix with potential LWD recruitment volumes explicitly considering spatialstructures of forests and the effect of root reinforcement. This probability matrix is the finaloutcome visualizing the probability of hydraulic and geotechnical bank erosion, as well as shallowlandslides contributing to LWD recruitment in mountain catchments. The preliminary resultsof this work are discussed in the context of a case study in the Swiss Prealps. The applicationof this proposed framework aims to improve the prediction of LWD recruitment in mountaincatchments in practice and to quantify the efficiency of forests along mountain streams.

Keywords: Large woody debris recruitment, large wood recruitment, effects of vegetation, modeling


235



Effect of riparian vegetation roots on development of meanderbends in Tarim River, Northwest China

Guo-An Yu ∗† 1, Zhiwei Li 2, He-Qing Huang 1, Wei-Wei Yao 1

1 Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences –China

2 School of Hydraulic Engineering, Changsha University of Science & Technology – China

Meandering channel with distorted bends develops along the Tarim River, the longest dry-land river in China. The river bank and bed is majorly composed of coarse silt and fine sandand almost none clay content, making the bank strength very low. The development of meanderbend in such environment hence is somehow irrational. We preliminarily investigate the effects ofriparian vegetation root on bend development in this region through examining the root cohesionand its enhancement on bank stability. In-situ measurements and sampling of roots from localtypical riparian vegetation (i.e., populous, Tamarix, and Phragmites Australis) were conductedto obtain root parameters like diameter and root area ratio. Local bend curvature correspondingto sampling sites are also obtained. BSTEM model is used to quantitatively estimate the effectsof different root conditions on improving channel bank strength. Four vegetation root scenarioswere modelled, i.e., tree (populous), shrub (Tamarix ), grass (Phragmites Australis) and no root.The results show that root supplies effective cohesive reinforcement for the channel bank andenhances the bank safety factors (Fs). Riparian vegetation should be a necessary condition fordevelopment of meandering channel in Tarim River.

Keywords: Tarim River, meandering channel, riparian vegetation, root, noncohesive bank


236



Bulk scaling of flow characteristics in the interior of sparse,emergent and rigid vegetation patch

Soumen Maji ∗† 1, Prashanth R. Hanmaiahgari 2

1 Central Institute of Technology Kokrajhar (CIT Kokrajhar) – Rangalikhata, Dist: Kokrajhar BTAD,Assam 783370 – India

2 Indian Institute of Technology (IIT) – Kharagpur, Westbengal 721302– India

Vegetation has an important role on erosion and sedimentation of rivers, river bank andmarshy lands, etc. This effect depends on type of flow characteristics present in a vegetationpatch. However, it is a great challenge to find out the flow characteristics in the interior ofvegetation patch. The objective of this study is to determine the appropriate scaling of flowcharacteristics throughout the interior of an emergent and sparse vegetation patch for a givenflowrate and depth, which can be used to predict the flow field in a similar vegetation conditions.In this study uniform acrylic cylinders were planted in a structured array to create a vegetationpatch. Two different flow conditions by varying aspect ratio for a given Reynolds number wereused in this laboratory study. Nortek ADV was used for measuring point velocities in the interiorof the vegetation patch. Mean flow and turbulence quantities at all the measuring locations inthe interior of the patch were scaled appropriately so that they collapse on a single curve. Thelocal maximum velocity is found to be an appropriate scaling parameter for normalizing thestreamwise velocity profiles, further the scaled velocity in the interior of the patch found to befollowing a power law. Lateral and vertical velocities in the interior of the patch are appropriatelyscaled by velocity vector across the section. Average bulk lateral velocity and scaled shear stressin a sparse and emergent vegetation patch can be described by linear equations in terms ofscaled depth.

Keywords: Scaling, Emergent vegetation, Sparse vegetation, Power law, Turbulence, Open channel

flow.


237



Experiments with sediment replenishment in a residual flowreach: comparison of field data with laboratory experiments

Severin Stahly ∗† 1, Anthony Maıtre 1, Mario Franca 1,2, Christopher Robinson 3, AntonJ. Schleiss 1

1 Laboratory of Hydraulic Constructions (LCH), Swiss Federal Institute of Technology Lausanne(EPFL) – Station 18; CH-1015 Lausanne – Switzerland

2 River Basin Development Chair Group, Delft Institute of Water Education (IHE) – IHE Delft POBox 3015 2601 DA Delft – The Netherlands

3 Aquatic Ecology Department, Swiss Federal Institute of Aquatic Science and Technology (EAWAG) –Uberlandstrasse 133, CH-8600 Dubendorf – Switzerland

Hydropower is an important pillar of the electricity production in Switzerland and its exten-sion is planned in the next decades. Therefore, a more sustainable management of hydropowerplants is needed. Sediment replenishment combined with artificially-triggered flood pulses aregaining increasing interest to restore residual flow reaches. In the Sarine river in Switzerland,such a measure was conducted. Mimicking laboratory experiments for the first time, four de-posits, totaling 1000 m3 of sediment, were added to the river downstream of Rossens dam. Some489 pebbles were equipped with RFID PIT tags and distributed among them. After the floodpulse passed, 57% of the tags were re-located. The maximum detected travel distance of a pebblewas 284 m. Some deposits were eroded, while others resisted. Due to a limited submergence,mainly lateral erosion was observed. Nevertheless, erosion of deposits as well as deposition oferoded material in clusters resulted in the same scheme as observed in laboratory experimentswhich could be validated with this field experiment.

Keywords: Sediment replenishment, River restoration, PIT tags, RFID, Artificial flood release,

environmental flow


238



Hydraulics of braided river dynamics; Insights from flumeexperiments

Riccardo Vesipa ∗† 1, Carlo Camporeale 1, Luca Ridolfi 1

1 DIATI Politecnico di Torino (Polito) – Corso Duca degli Abruzzi, 24 10129 Torino – Italy

Braided rivers are peculiar morphologies that occur in water courses characterized by highsediment load and slope. They are characterized by multiple channels which undergo a con-tinuous spatiotemporal evolution. Braided river landscapes are very sensitive to hydrologicalchanges: recent climate changes and river damming are inducing braided rivers to evolve tomeandering or pseudo-meandering rivers, with strong environmental impacts.As complex phenomena drive the braiding process (e.g., flow bifurcations at island edges, par-tition and confluence of water and sediment discharges in the channel network, sediment ero-sion/sedimentation along channels, etc.), a satisfactory knowledge of braided river dynamics isfar to be reached. For this reason, new research efforts are required. To this aim, flume exper-iments are a key tool, as they can reproduce some fundamental mechanisms occurring in theseriver systems. However, technical issues generally limit an accurate survey of the flume topog-raphy and its temporal evolution. In fact, although high-precision laser scans are used, waterrefraction hampers the direct measure of the bed topography in water-covered flume channel.Therefore, the removal of water is mandatory before the laser survey. This emptying/refillingprocedure alters the flume topography, makes the study of the temporal evolution of the systemvery difficult, and render the evaluation of the hydraulic characteristics of the channels (waterdepth, stream velocity, channel width) impossible. In order to measure at the same time thebed-elevation of the flume-river-model and the position of the free surface, we have setup anexperimental facility that combines the use of a laser-scan and an ultrasonic sensor. The ultra-sonic sensor measures the position of the free surface, whereas the laser-scan the elevation ofthe bottom. This last measure is affected by a refraction error, which can be corrected, as theposition of the free surface is known (Visconti et al., 2012).To generate braiding channels, the erodible-bed flume of the Hydraulics Laboratory of the Po-litecnico di Torino was used. Its size is 18x2 m, and it is filled with sand of 0.45 mm meandiameter. The laser-sonar-sensor is mounted in a frame with numerically controlled axis. Thelaser-sonar-sensor repeatedly goes from one bank side to the opposite bankside, and acquireswith high temporal (30 profiles/hour) and spatial (3000 points/m) frequencies the profile of ariver transect (elevation of both bed and free surface).The runs are as follows (Vesipa et al., 2017): water is let flow in a flat floodplain crossed by arectangular straight channel. Alternate or multiple bars form, and quickly evolve to a braidednetwork. After a few hours a dynamic equilibrium is reached. Several runs with slopes andflow discharges in the range [0.5%-1.5%] and [0.5 l/s -1.5 l/s] were performed, and lasted tensof hours. The flume data acquired are used to investigate the following aspects: (i) the tempo-ral variability of some key hydraulic characteristics (e.g., water depth, stream velocity, channelwidth) of a selected transect; (ii) the quantification of the dynamic equilibrium point of thesehydraulic characteristics, and (iii) the role of the dimensionless stream power and flow rate.

Keywords: braided rivers, flume experiments, spatiotemporal morphological dynamics, new exper-

imental techniques, statistical analyses


239



Limiting the development of riparian vegetation in the IsereRiver: physical and numerical modelling study

Nicolas Claude ∗† 1, Kamal El kadi Abderrezzak 1,2, Marion Duclercq 1, Pablo Tassi 1,2,Clement Leroux 1

1 Laboratoire National d’Hydraulique et d’Environnement (LNHE) – EDF R&D – 6 quai Watier, 78401Chatou cedex – France

2 Laboratoire dHydraulique Saint-Venant – Ecole des Ponts ParisTech, EDF R&D, CEREMA – 6 quaiWatier, BP49, 78401 Chatou cedex – France

The Isere River (France) has been strongly impacted during the 19th and 20th centuries byhuman activities, such as channelization, sediment dredging and damming. The hydrology andriver morphodynamic have been significantly altered, leading to a riverbed incision, a decreasein submersion frequency of gravel bars and an intense development of riparian vegetation on thebars. The flood risk has been increased due to the reduction of the river flow conveyance, andthe ecological status of the river has been degraded. Physical and numerical modelling stud-ies are performed to evaluate the impact of the modification of the current hydrology (mainlycontrolled by dams) and the definition of new bed cross-sectional profiles, which are expectedto foster the submersion frequency and mobility of the bars, thus limiting the riparian plantdevelopment.The flow and sediment transport numerical simulations are performed with the Telemac Mod-elling System (www.opentelemac.org). The flow routing is based on the solution of 2-D depth-averaged shallow-water equations, with closure relationships for turbulence and bed roughness.The sediment transport routing treats bed load and updates the channel bed by solving theExner equation.The experimental setup consists of a 1:35 scale, undistorted movable bed designed to ensure thesimilarity of Froude number and initial conditions for sediment particle motion. The physicalmodel is 35 m long, 2.6 m wide, with sand mixture composed of three grain size classes. Un-steady flow and inlet bed load conditions are run to analyse the mobility of gravel bars.The numerical and physical models are applied on a new bed morphology obtained after re-shaping a long vegetated bar into small central gravel bars, and removal of plants and a layercomposed of fine sediments.The numerical simulations show that the new bed configuration allows submersion of bars for20% of the time between April and July, which should likely limit the plant recruitment. Lab-oratory experiments demonstrate that the dynamic of bars is strongly affected by the sedimentsupply. Bars become sufficiently mobile, limiting the recruitment of seedlings after 10 days witha flow discharge higher than a 5-year flood combined with a high sediment supply.This study is supported and funded by the Agence de l’eau Rhone Mediterranee Corse.

Keywords: flood regulation, bar, morphodynamic, riparian vegetation


240



Self-adjustment process of flow pathway in a narrow curvedchannel

Hiroshi Hayakawa ∗† 1, Tomonori Kitao 2, Nobuo Sato 3

1 Kitami Inst. Technology – 165 Koen-cho, Kitami, Hokkaido – Japan2 Takenaka Civil Eng. & Const. Co., Ltd – Japan

3 Sumitomo Mitsui Const. Co., Ltd. – Japan

The Kushiro Wetland, which is located in the east of the island Hokkaido, is the largestone in Japan. There nurtures a rich diversity of plants and wildlife including Japanese cranes.However, this wetland has suffered from various human disturbance in particularly the mostrecent decade, and there the ecosystem considerably has been felt stress. In FY2002, naturerestoration project of the Kushiro Wetland, which was registered under the Ramsar Convention,has been started as a pioneering case of nature restoration in Japan.As part of nature restoration projects on the Kushiro River, Japan, a river reconstruction projectwas planned for the Kayanuma District along the edge of the Kushiro Wetlands. This projectfocused on river environment conservation and restoration, wetland restoration, and sedimentinflow control by returning the straightened river channel to its old meandering form (KushiroDCD, 2006).After the reconstruction of the old channel, the river was shifted to that channel in February2010; the backfilling of the straightened channel and removal of surplus soil on the right bankwere completed in 2011(Kushiro WNRC, 2011). At the curved inlet (distance mark KP 33.4)of the old meandering river, where the narrowed (30 meters width) channel joins the wider (80meters width) straightened channel, the initial intention was to develop riverbed scouring alongthe outer bank of the curved channel where the water’s flow would be directed.However, in actuality, sediment deposits and backfills along the outer bank autonomously andgradually narrowed the flow path width and directed flow along the inner bank of the curvedchannel, forming a flow path close to the old river channel. This is similar to the channelnarrowing mechanism pointed out by Fujita (2007) in Channel Segment 2-2: Sand-bed River,in which narrowing occurs along a new river bank due to a high-water channel formed bysediment deposited in a low-water channel whose width was increased by river improvement.Channel overflow easily occurs at this inlet, and this plays a role in controlling the transportand deposition of suspended sediment during such flooding events. In order to maintain thisrole, it is necessary to identify the future fluctuations of the riverbed and the flow pathway ofthe channel inlet.This study investigated the formation mechanism of the flow pathway formed in the narrowedchannel inlet by clarifying the pathway’s fluctuations according to field surveys and laboratorytests, which reproduced and verified the pathway fluctuation characteristics. From field survey,in response to change in water and sediment discharges, significant streamwise variation in waterflow width in the curved channel adjusts in order to establish the dynamic equilibrium. Alongthe outer bank of curved channel, the secular bed deposit beside the outer bank is increasing,and as a result, the main streamline flows into the old river along the inner bank as left bank.Moreover, this narrowing curved channel easily leads to overspill some flood water including richsuspended sediment and to deposit some fine sand near channel side flood plain.We intend to explain above significant bed variations by using movable bed experiments withthe distorted model and the numerical simulations. We used a hydraulic model experimentto reproduce and examine the bed fluctuation of the original river (prototype), by setting its


241



original form to the curved channel of the old river reconstruction zone between KP 33.40 andKP 34.00 (main river zone) and between SP2200 and SP2350 (old river zone) of the KushiroRiver in Kayanuma District; this model assumes overflow in order to examine the conditions forthe formation of flow paths around the curved channel. As the existence of the pointbar on theright bank of the curved channel (KP 33.60) is important for considering the width-narrowingmechanism according to the field surveys, we examined the bed fluctuations of the curved channeland the width variations both when this pointdbar moves and when it does not move becauseit is covered by plants as in the field. As a result, we suggest, though qualitatively, that theexistence of the sandbar upstream of the curved channel causes the autonomous specification ofthe flow path width in the curved channel with a narrowing width, and that this flow path isformed.

Keywords: Nature restoration, Narrow curved channel, Flow pathway, Riverbed fluctuation

242


Morphological development of river widenings with variablesediment supply

Cristina Rachelly ∗† 1, Volker Weitbrecht 1, David F. Vetsch 1, Robert M. Boes 1

1 Laboratory of Hydraulics, Hydrology and Glaciology; Swiss Federal Institute of Technology Zurich(VAW, ETH Zurich) – Switzerland

In the past, numerous rivers were artificially confined to a narrow riverbed designed toefficiently transport discharge and sediment. Additionally, the sediment continuum of riverswas interrupted by structures like weirs or sediment retention basins. The resulting sedimentdeficit together with the lateral confinement transformed dynamic alluvial river systems withextensive floodplains into straight rivers with a flat bed that are incised in their alluvium. Thelack of morphological variety leads to homogeneous flow depths and velocities and therefore auniform habitat not capable of suiting the diverse needs of flora and fauna. In addition, shallowand structured banks are missing despite their importance for a functioning lateral connectionbetween aquatic and terrestrial habitats.Due to recent adaptions in the legal framework of many countries, efforts to mitigate negativeeffects of lateral confinement and sediment deficit have strongly increased (e.g. Swiss FederalAct on the Protection of Waters 2011, EU Water Framework Directive 2000). The removal ofsediment barriers or the replenishment of sediment are measures to increase sediment transportand partly restore the natural sediment continuity. River widenings varying in length from afew hundreds of meters up to several kilometers are popular measures to recreate a dynamicwidth development and to initiate change of river bedform. In order to accurately predict thebenefits of a river widening, it is crucial to attain a sound understanding of the relation betweenriver width and resulting morphology in the case of variable sediment supply. Moreover, thebenefits of increased sediment supply for the morphology of sediment deficient river wideningsneed to be understood. Aspects such as the reach-scale sediment balance, vegetation, and grainsize distribution also have to be considered.This study is part of the transdisciplinary research project Riverscapes – Sediment dynamics andconnectivity and is co-financed by the Swiss Federal Office for the Environment (FOEN). Thescope of this study is to improve the knowledge about morphological processes and to identifymeasures to influence the development of ecologically valuable habitats in river widenings. Thetopic is investigated by combining laboratory flume experiments and numerical modelling. As afirst step, this paper reviews previous research on the topic, identifies research gaps and presentspotential for future research.

Keywords: sediment replenishment, river widening, river restoration


243



Calibration procedure of hydraulic simulations for themicrohabitat method.

Ludovic Cassan ∗ 1, Helene Roux † 1, Dominique Courret 2, Sylvain Richard 2

1 Institut de Mecanique des Fluides – Univ. Toulouse, CNRS, INPT, UPS – allee du professeur CamileSoula 31400 Toulouse – France

2 Agence Francaise pour la Biodiversite (AFB) – Pole ecohydraulique – allee du professeur CamilleSoula 31400 Toulouse – France

Hydropower plants can profoundly modify the natural morphology and hydrology of riversand can alter the functionality of habitats for fish living and reproduction. In particular, hy-dropeaking leads to rapid and frequent changes of the hydrodynamic conditions and it is crucialto ensure aquatic habitat quality is maintained as much as possible during these periods. Onepresent method to determine mitigation measure (minimum and maximum flow, rate of change)is to perform hydraulic simulations in 1D or 2D in the range of flow variation and to evaluatehabitat quality for fish with the microhabitat method. The hydraulic model calibration has tobe conducted carefully since the model has to reproduce precisely the hydraulic conditions fromlow to high flow rates (up to several times the mean flow of the rivers). Within this range, thefriction coefficient can evolve greatly because at low flows the size of roughness elements becomecomparable to the water depth.. This phenomenon is observed by performing the modelling andthe calibration at 2 stations on a river in French Pyrenees with different cross section shapes,one with progressive overflowing of some banks with large blocks and the other one withoutsuch phenomena. Thanks to field measurements of water levels at low and high discharge, thecalibration process has shown that the friction coefficient can be multiplied by 2 as a functionof the discharge. The paper proposes a methodology to evaluate the most appropriate tool. Aswater depth is concerned, the 2D simulations (TELEMAC 2D) provide similar results to thoseobtained with 1D (HEC-RAS) because flow remains unidirectional. Then a sensitivity analysisis carried out to estimate the uncertainty on the fish habitat outputs for a fish species (browntrout in the present study) resulting from several widely used friction laws. These friction lawscan lead to different conclusions about habitat suitability depending on the calibrated coeffi-cient. Finally, to perform relevant habitat modelling, it is necessary to measure water levels atseveral discharges and to describe accurately the spatial variability of roughness height.

Keywords: habitat, roughness calibration, hydropeaking


244



A study on the applicability of optical remote sensingtechniques in river

Ji Hyun Kim ∗† 1, Joongu Kang 1, Changsung Kim 2, Hongkoo Yeo 1, Namjoo Lee 3

1 Goyang-si, Gyeonggi-do, 10223 – South Korea2 Goyang-si, Gyeonggi-do, 21759 – South Korea

3 309, Suyeong-ro, Nam-gu, Busan – South Korea

Since the recent development of UAVs and digital sensors technology has enabled the ac-quisition of high-resolution image data, it is considered that the image data of riverside canbe analyzed. Therefore, this study analyzes the applicability of remote sensing techniquesthrough image analysis in river systems and habitats. The target stream in this study wasthe Cheongmi-stream and the applicability of the river environmental evaluation technique wasanalyzed through image analysis. The satellite images used for the analysis of river topographyand environments were compared with the aerial images taken by a micro unmanned aerial vehi-cle (UAV), and the river environmental evaluation was carried out with the field research at thesame time. The data acquisition range and application limit by river environmental evaluationtechnique proposed previously were evaluated, and as a result, it was found that it was possibleto draw various evaluation parameters using a drone that could take an image at a low altitudein comparison to satellite images

Keywords: Optical Remote Sensing, River, Stream environmental assessment, image analysis


245


Poster session P.B – Hydraulic structures and their effects on bed, flow regime and ecology

Estimating large woody debris volume and distribution floatedand accumulated in reservoir using aerial photographs

Waku Suzuki ∗† 1, Sohei Kobayashi 1, Sameh Kantoush 1, Yasuhiro Takemon 1, TetsuyaSumi 1

1 Kyoto University – Japan

Large woody debris (LWD) could increase the risk of flooding in the event of heavy rainfall,and fast estimation of the accumulated LWD is crucial for river basin management. We develop amethod to automatically detect LWD floating in reservoirs using airborne images, and estimatedthe total volume of LWD accumulated in a reservoir during a severe flood event in northernKyushu, Japan, early July 2017. The LWD was successfully extracted from the images based oncolour and brightness by using ImageJ. The total volume of the accumulated LWD estimatedfrom images was similar to the LWD volume actually removed from the reservoir by the endof October. Most LWD pieces were concentrated in the upstream-side of the reservoir, and alongitudinal variation in density and length of LWD pieces was also evident.

Keywords: flood, reservoir, large woody debris, image analysis, accumulation, production


246



Degradational response of engineered alluvial channels tochanges in the upstream controls and channel width: Simplified

1D numerical simulations

Meles S. Tewolde ∗† 1,2, Enrica Viparelli 1, Astrid Blom 2

1 Department of Civil and Environmental Engineering, University of South Carolina, Columbia –United States

2 Delft University of Technology, Faculty of Civil Engineering and Geosciences, Department ofHydraulic Engineering – The Netherlands

In response to changes in the upstream controls (i.e., the water discharge, the sedimentsupply rate, and the calibre of the load), engineered alluvial channels adjust their bed slopeand bed surface texture to establish a new equilibrium state. The time scale of adjustment toestablish the new equilibrium state following changes in controls is called the relaxation time(Howard 1982). De Vries (1975) and Howard (1982) discuss the time scales of the response of thechannel gradient to base level lowering and decrease of upstream sediment supply, respectively.Both studies were limited to unisize sediment. We extend these studies by considering mixedsize sediment, and focusing on its equilibrium state, transient response and related adjustmenttime scales to changes in the upstream controls and channel width. To this end, a 1D numericalresearch code (Elv) (Blom et al 2017, a, b) is used. The code solves for the flow, bed level, andbed surface texture using the backwater equation and the Hirano equations (Hirano, 1972). Thecode is applied to one dimensional schematic river 100 km long river reach consisting of twograin size fractions: gravel (D50 = 10 mm) and sand (D50 = 1 mm). The characteristics of theschematic reach is loosely based on the characteristics of the Waal River, which is a branch ofthe Dutch Rhine.We illustrate that the following perturbation to an initially equilibrium state lead to a degrada-tional response: an increase of the water discharge, a decrease of the sediment supply rate, anincrease of the sand content of the sediment supply, an increase of the gravel content of the sed-iment supply, and a decrease of the channel width. Degradational response under all conditionsis associated with surface coarsening. The equilibrium states of the numerical simulations agreewith analytical solutions. The results provide insight into the current degradational response ofengineered rivers, such as the Rhine River, the Elbe River and the Danube River.

Keywords: mixed size sediment, degradation, adjustment time scale


247



Experimental study of the bed morphology downstream of asluice gate

Luıs Carvalho 1, Elsa Carvalho 2, Rui Aleixo 3, Maria Manuela Lima ∗† 1

1 Escola de Engenharia da Universidade do Minho – Campus de Azurem, 4800-058 Guimaraes –Portugal

2 Faculdade de Engenharia da Universidade do Porto – Rua Roberto Frias s/n, 4200-465 Porto –Portugal

3 Universidade de Bolonha – Via del Lazzaretto 15/5, 40126 Bolonha – Italy

Scour can occur next to obstacles or due to the lateral contraction of the flow, and it isoften associated with the collapse of hydraulic structures (Richardson and Davies, 2001; Deyand Raikar 2007; Dey and Sarkar 2006). It is necessary to predict the maximum scour deptharound obstacles, such as sluice gates, to avoid accidents that could affect their stability andendanger human lives. Furthermore, the morphology of the river bed downstream is affected byscour and a dune or bar is formed, introducing severe changes in the flow and sediment transport(Oliveto and Hager, 2014).The scour downstream of a sluice gate is originated by a turbulent submerged horizontal jet,usually considered to be two-dimensional (Melville, 2014). The conjugation of sluice gate openingdimension, tail water depth, flow rate, as well as the existence of an apron results in different jetsthat can be accompanied by a hydraulic jump. The flow is highly turbulent, even for relativelylow jet Froude numbers, and a scour cavity develops at different rates depending on the sedimentsize and its nonuniformity (Melville and Lim, 2013). Besides the prevision of the maximumscour (e.g. Aamir and Ahmad, 2016) that allows the correct design of such structures, the duneevolution downstream can provide insights into the sediment transport mechanism (Oliveto andHager, 2014).The scour downstream a sluice gate was studied experimentally using a flume, 615 mm long, 150mm deep and 15 mm wide. A sluice gate with an opening of 6 mm was used. The bottom of theflume consisted of an apron with variable length between 0 and 100 mm. Downstream the apronthere was a sediment box (62 mm deep) filled in with 2 mm glass beads. This kind of idealizedsediment bed was adopted in order to neglect the effect of sediment nonuniformity. Due to thesmall transversal dimension of the flume the sediment bed morphology could be easily visualizedand monitored by means of video recording. The sediment bed size allowed the particles to bewell identified in the images, resulting in a clear definition of the sediment surface during theexperiments. Image processing was performed allowing the identification of the bed longitudinalprofiles after the scour process had begun.Results show the temporal evolution of the scoured cavity profile for different flow conditions.The influences of the apron length and tail water depth were determined.

Keywords: scour, sediment transport, dune formation, dune migration, image processing


248



Measurement and control of high suspended sedimentconcetration during Kurobe river sediment flushing with

sumersible type SMDP

Tetsuya Sumi ∗† 1, Saichiro Morita 2

1 Water Resources Research Center, Disaster Prevention Research Institute, Kyoto University – Japan2 SMD Engineering, Co., Ltd. – Japan

In the Kurobe River, coordinated sediment flushing and sediment sluicing of Dashidairaand Unazuki dams have been executed since 2001. From the view point of the comprehensivesediment management in the sediment routing system, monitoring of quantity and quality ofsediment transport during these events in rivers and reservoirs is very important. This papershows the results of continuous measurement of high suspended sediment concentration duringsediment flushing and sluicing operation of Unazuki dam in 2015 and 2016. These data havebeen obtained by submergible type of Suspended Sediment Concentration Measuring Systemwith Differential Pressure Transmitter (hereinafter we call ‘submergible type SMDP’) which isdesigned to be placed underwater.The SMDP has advantages in long-term and high turbidity measurement because differentialpressure transmitter is measuring density of water directly. Based on measuring conditions,a submersible type and a water circulating type SMDP are available, and both of them haveshown good performances through laboratory tests and field experiments in the Kurobe river.Measured data have good correlation with manual sampling and show high concentration peaksup to 50,000mg/l which were not obtained by scattered hourly sampling data. In 2016, thesedata were effectively utilized to control gate operation by real-time basis during the most criticaltiming producing extreme high concentration just before free flow starts for sediment flushing.

Keywords: Sediment Flushing, Reservoir Sedimentation, Turbidity Measurement, Suspended Sed-

iment Concentration


249



Experimental study of the velocity field induced by a propellerjet in an inland-ship model and the related bed scour

Francisco Nunez-Gonzalez ∗† 1, Katinka Koll 1, Detlef Spitzer 2

1 Leichtweiß-Insitut fur Wasserbau, TU Braunschweig (LWI) – Beethovenstr. 51a, 38106 Braunschweig– Germany

2 Federal Waterways Engineering and Research Institute (BAW) – Germany

The highly turbulent flow induced by ship propellers has a great potential to scour thealluvial bottom of navigational rivers and canals. Characterization of the complex flow fieldbehind propellers is essential for forecasting the scouring action. In this study the velocity fieldand scour induced by two standard arrangements of propeller, nozzle and rudder from inlandvessels are investigated experimentally with a ship model on a scale of 1:16. There are twoobjectives: first, to identify the influence of the ship stern on the flow field, and second, toassess induced scour depths in relation to maximum current velocities close to the bottom. Itis found that the equilibrium scour depths for the two propeller arrangements are of the sameorder of magnitude, but that the time development of scour is different. The differences can beexplained by the converging trend of the flow velocities at the bottom level for the two situations,when the vertical distance between the propeller and the bottom is high. It is also shown thatexisting relations for the velocity field require amendment when the propeller is ducted, and foradequately considering the effect of the ship stern and rudder type.

Keywords: Scour, velocity field, physical modeling, experiments, ship propeller, inland vessels,

propeller jet


250



Evaluating an optimum slit check dam design by using a 2Dunsteady numerical model

Samkele Tfwala ∗ 1, Su-Chin Chen † 1

1 Department of Soil and Water Conservation, National Chung Hsing University, 145 Xingda Road,402, Taichung – Taiwan

Debris flow could be catastrophic to residents and property located at their downstream.As a result, engineers have designed several structural countermeasures, such as check dams.Regardless of the many investigations on check dams, uncertainty with respect to their design isstill persistent. Against this backdrop, the study aims to assess the efficiency and determine anoptimal design of slit check dams for mitigating debris flow and sediment-laden flows in steepchannels. The study uses an actual slit check dam located at Landao creek, a tributary to theBeng-gai River in the central range of Taiwan. The creek has an average slope of 7 degrees, whileits d50 is approximately 100 mm. Steep slopes, extreme precipitation, poor geologic formations,debris flow and landslides characterise the catchment. Concerning the slit check dam design;there were six rectangular concrete piers (width = 1.5 m, length = 4 m, depth = 8 m), linearlyspaced at 1 m in a 180◦ alignment layout, with the middle 2 piers height reduced by 2.5 m. Weevaluated the performance of this configuration and further tested two additional configurationsby cutting a single pier and three piers at the centre in a 2D model, Nays-2DH. Hydrographof a selected storm was used for upstream boundary conditions. Surveys using an unmannedaerial vehicle were conducted pre- and post-storm events to validate numerical solutions. Scourand deposition profiles from the different pier configurations formed the basis of our assessment.The numerical computations yielded valuable results and may provide better understanding inthe optimal design of slit check dams. Our findings are of paramount importance to engineersand decision makers with regard to debris flow mitigation, especially in a typhoon prone regionlike Taiwan.

Keywords: bed evolution, slit check dams, debris flow, sediment transport


251



Scour monitoring on bridge pier – methodology andimplementation

Emma Florens ∗ 1, Christophe Chevalier 2, Frederique Larrarte † 3, Franziska Schmidt 4,Edouard Durand 5

1 Railenium – France2 IFSTTAR/GERS/SRO – 14-20 Boulevard Newton 77447 Marne-la-Vallee Cedex 2 – France

3 IFSTTAR/GERS/EE – Route de Bouaye - BP 4129 44341 Bouguenais Cedex – France4 IFSTTAR/MAST/SDOA – 14-20 Boulevard Newton 77447 Marne-la-Vallee Cedex 2 – France

5 Cerema – Ministere Ecologie, Developpement Durable Energie – Blois – France

Scour represents a significant contributing factor in structures destruction. Managing thescour risk on bridge piers and abutments, road or rail type, exposed to natural hazards consti-tutes a major challenge to sustainable development and land use planning. For example, theFrench railway network includes 1,700 river-crossing structures and a tremendous length of em-bankments either forming river banks or adjacent to watercourses exposed to scouring processes.The problem is more pronounced for road infrastructure, with for example, more than 2,000 roadbridges over rivers identified within the primary road network for France’s Gard Departmentalone.Funded by the French Research Agency, the SSHEAR project, acronym for ”Soils, Structuresand Hydraulics: Expertise and Applied Research, has been set up to improve scour mechanismsknowledge, to develop innovative experimental and observational tools and hydraulic numeri-cal models at both laboratory and full-scale, and then to build optimized diagnostic, warningand management methods for bridges operators. The strength and originality of the SSHEARproject lies in the combination of various techniques, methodologies and models, such as ex-perimental and numerical methods, in addition to collecting interdisciplinary expertise, such asgeotechnical, hydraulics, structural engineering, sedimentology, as well as mixing operators andacademicians. Shared knowledge, transfer, exchange of techniques and widespread possibilitiesfor discussion among all partners are also the main asset of this project.Physical and numerical progress in both sedimentary hydrodynamics and soil mechanics allowconsidering a comprehensive study characterizing the scour hazard by means of innovative in-strumentation based on the recent improvements in acoustic technics for bathymetry, flow andvibrations measurements.The field part of SSHEAR seeks to develop tools and a methodology expected to lead to animproved characterization and monitoring of sites with regards to the problem of structuralscouring. The first step has been to identify pilot sites, representative of scour vulnerability.The aim is to equip these pilot sites with a bedform ”scour” monitoring system such as a 3Dvelocimeter (ADCP type), to assess the turbulent shear stress, and bathymetry measurements,with high resolution sonar, to better characterizing the susceptibility of in situ sediment toerosion. These several sensors will be installed adjacent to or on the structures to measure andtrack continuously the scour parameters. Other sensors, such as vibration sensors, will alsobe placed on the structures. Monitoring devices will be left in place for a full year. Databasestatistical analysis will then allow assessing the flow ability to favor or disadvantage pier scour.A search of systems available on the market has been conducted, focusing on measurementsprecision and resolution, system autonomy and wireless data transmission to test the possibilityfor an infrastructure manager to simply implement a monitoring system. Instrumentation, sen-sor adaptability, limitations (actual measurement ranges, plus ergonomics, energy supply limits)and in situ implementation will be presented and discussed at the conference.


252



Keywords: bridge, piers, abutment, scour, in situ experimentation

253


Factors influencing the sediment delivery ratio of the ThreeGorges Reservoir

Dayu Wang ∗† 1, Chunhong Hu 1, Chunming Fang 1, Jianzhao Guan 1, Lei Zhang 1

1 China Institute of Water Resources and Hydropower Research, Beijing, P.R.China – China

In recent years, the sediment delivery ratio (SDR) of the Three Gorges reservoir (TGR) hasnoticeably decreased as a result of the increase in water levels at the dam site and the decreasein inflow of fine particles, thereby resulting in increased reservoir siltation. Therefore, it is vitalto research the factors that influence the SDR of the TGR. Factors that could have impacton the SDR were studied using TGR monitoring data. The study indicated that the waterlevel at the dam site and inflow and outflow rates could have contributed to the change in theSDR. A sensitivity analysis of the influencing factors was then carried out using a mathematicalmodel to simulate numerous sediment movement scenarios in the TGR. By changing the inputconditions of the model, sufficient results were obtained to enable a sensitivity analysis of eachfactor. The results showed the flood retention time (FRT)-the ratio of reservoir capacity toaverage outflow discharge-was the principal factor influencing the SDR. The other factors (inflowsediment concentration, inflow sediment coefficient, inflow sediment gradations, and the shapecoefficient of the inflow flood shape coefficient), also had an influence on the SDR. However,under different levels of FRT, their degrees of influence on the SDR were not the same.

Keywords: the sediment delivery ratio (SDR), the Three Gorges reservoir, sediment transport


254



Experimental study of submerged vanes in intakes undersediment feeding conditions

Asli Bor Turkben footnoteSpeaker∗ 1

1 BOR.A.T – Turkey

Sediment is transported along the river flow and deposited in the mouth of the intake struc-ture over time and reducing the water intake capacity. Nowadays, many water intake structureslose their function and are closed to operation. To deal with this problem, recently, submergedvane application has offered a practical and economical solution. Submerged vanes generatea secondary circulation in the flow and change the magnitude and direction of the bed-shearstresses. As a result, the riverbed aggrades in one portion of the channel and degrades in another.Thus, sediment accumulates in the main channel in a controlled manner and preventing it fromentering the water intake channel. The aim of this study is to evaluate the efficiency of threevane installations under sediment feeding conditions by comparing the bed topography beforeand after vanes were installed. For that purpose, experiments were carried out in a laboratorychannel running for 90-degree intake angle. Three vanes were installed in one column at nearthe intake entrance. The vanes dimensions were calculated according the criteria provided byOdgaard and are equal to; 3cm height, 12cm long, 10 mm thick, and aligned with α = 20◦ angleto flow direction. The tests were run until equilibrium was reached, i.e. when the outgoing soliddischarge was equal or larger than 90% of the incoming. Once the bed topography remainedstable, bed and water level surfaces were measured. tests were carried out by feeding sedimentfrom upstream of the main channel.

Keywords: Submerged vanes, local scour, sediment feeding, intakes, sediment transport, experi-

mental hydraulics


255



Three dimensional flow structures around a deep scour hole

Akihiro Tominaga ∗ 1, Naohiko Sassa † 2, Yuji Hara 1, Yuka Kuno 1

1 Nagoya Institute of Technology (NIT) – Japan2 CTI Engineering (CTIE) – Japan

A large scoured area with 20 m depth in maximum is observed besides the convex riverbank in the Kiso River. Expanding of the scour has possibility of causing destabilization anddamage to hydraulic structures. It is necessary for river control and maintenance to make clearthe generation mechanism of such a deep scouring.From the velocity vectors in horizontal plane measured by using a floating ADCP around thescoured area, a counter-clockwise planform vortex is observed just on the largest scour hole. Thisvortex is continuously exist in the vertical direction and rather strong velocity is recognized evennear the bottom. The existence of this planform vortex is considered to be one of the causes ofdevelopment and sustention of large-scale local scouring in the Kiso River.In order to make clear the three dimensional flow structures in this deep local scour, we conducteda field observation and model experiments. Three ADCPs were set on the bottom around thedeepest scour hole and vertical velocity profiles were measured continuously with an interval of1 minute during two weeks. In this term, small floods occurred twice. From the result of ADCP,the velocity in the hole was increasing and the vertical vortex was developing, with an increaseof river discharge. It is indicated that considerable magnitude of velocity was generated evennear the bottom by the action of vertical vortex.Furthermore, we performed laboratory experiments on a physical model of the bed form ofscoured area with a reduced scale of 1/259 in horizontal plane and 1/173 in vertical direction.The similar planform vortex was also reproduced in the model experiments. There exists veryfast flow even near the bottom along the center-side edge of the scour hole. This planform vortexis like a cylindrical tube with constant rotating velocity.It is presumed that the planform vortex is generated by the nonuniform adverse pressure gradientcaused by the sudden deepening in the stream. The existence of sudden drop of river-bed andside wall are necessary to generate the planform vortex. But it should be clarified more precisely.Once the planform vortex is generated, it contributes to develop and sustain the large-scale localscouring.

Keywords: local scouring, planform vortex, 3D flow structure, ADCP, model experiment, Kiso

River


256



Numerical Modelling of turbidity currents with ANSYS CFXand TELEMAC 3D

Magali Jodeau ∗† 1, Jiawei Feng 1, Sabine Chamoun 2, Giovanni de Cesare 2, Anton J.Schleiss 2

1 Laboratoire National d’Hydraulique et d’Environnement (LNHE) – EDF R&D – 6 quai Watier, 78401Chatou Cedex – France

2 Laboratoire de Constructions Hydrauliques - EPFL (LCH) – CH-1015 Lausanne – Switzerland

Turbidity currents occur in reservoirs when the density of the incoming flow is significantlydifferent from the still water of the lake. They may be a relevant lever to manage the accumu-lation of fine sediments in reservoirs.Many numerical studies on turbidity currents have been performed in the past. In this paper wepropose to show how two different numerical codes could simulate the propagation of turbiditycurrents. TELEMAC 3D and ANSYS CFX 17.1 solver were chosen as they are commonly usedby many research and engineering teams. The first code solves the Navier-Stokes equations andan advection–dispersion equation for sediment transport with the finite element method, severalturbulence models are implemented and the change of density due to sediments is taken intoaccount. The second is a CFD code, which also solves the Navier-Stokes equations using thefinite volume method. A multiphase flow model allows the simulation of flows having differentphases such as the case of turbidity currents. Sediment transport can be computed based on anEulerian-Eulerian or Lagrangian approach. In the former case (used in the present work), severalequations can be solved to compute interfacial area density and interphase transfer, defining thetransport of sediments. Similarly to TELEMAC 3D, different turbulence models are availablein the software.The simulations are performed on two configurations. The first case aims at modelling the plung-ing of a turbidity current, i.e. the location where the upstream dense flow plunges under thestill water. Numerical calculations with TELEMAC 3D are compared with theoretical formulaand show very good agreement. The theoretical velocity profiles are also well reproduced withthe numerical code. On this basic configuration, a sensitivity analysis is performed to identifythe most significant numerical and physical parameters.The second model is validated based on an experimental work performed at EPFL. The latterconsisted on testing turbidity current venting as a solution to manage reservoir sedimentation.A long and narrow flume was used to simulate the reservoir where a turbidity current was trig-gered. A wall was placed at the downstream side of the flume, along with a rectangular orificeacting as bottom outlet to evacuate turbidity currents. ANSYS CFX as well as the TELEMAC3D models successfully reproduced the experimental work. The parametric study was extendedusing the CFX model.Based on these two examples, the advantages and limits of both approaches are discussed inorder to supply guidelines for the modelling of turbidity currents in real reservoirs.

Keywords: turbidity current, modelling


257



Hydraulic potential of the Lower Vistula (Poland)

Michal Szydlowski ∗† 1, Romuald Szymkiewicz 1, Dariusz Gasiorowski 1, Jakub Hakiel 1,Piotr Zima 1

1 Gdansk University of Technology, Faculty of Civil and Environmental Engineering – GabrielaNarutowicza 11/12 80-233 Gdansk – Poland

The Vistula (Wisla) is the largest river in Poland. Its length is over thousand kilometersfrom the sources in the BeskidSlaski mountains up to the Baltic Sea (Gdansk Bay). From thehydrographic point of view the Vistula river can be divided into three different sections, likeupper Vistula, central Vistula and lower Vistula. The upper Vistula stretches from its sourceto the tributary San river, the central Vistula flows from the tributary San to the tributaryNarew and the lower Vistula runs from the tributary Narew to the Gdansk Bay of Baltic Sea.Lower Vistula (part of the river discussed in this paper) is almost four hundred kilometers longriver section extending from the tributary Narew to the outflow to the Baltic Sea. The averagedischarge of the Vistula at the mouth of the river is about 1080m3/s. Due to this relatively highflow rate, the lower Vistula has a quite large hydro-energy potential. The hydropower potentialof Polish rivers is relatively small and unevenly distributed. The Vistula accounts for the largestpart (approx. 80%), with approx. 65% of the potential in the lower Vistula. This represents33% of the technically usable hydropower potential in Poland, which corresponds to the yearlyaverage energy output of 4000 GWh. Moreover, it should be emphasized that Poland uses only11% of its available energy potential of rivers, which puts it in the last place in Europe.In the 17th century the Vistula was the most navigable river in Europe. After partitioning ofPoland in the 18th century the Vistula lost its significance, while other European rivers devel-oped very dynamically as waterways, as well as sources of hydro energy and water for households,industry and agriculture. Now the lower Vistula should provide a navigation connection to theEurope forming water routes E70 and E40. However it does not meet the criteria required forthe international waterways.There have been many plans for the development of the lower Vistula river so far. Unfortu-nately none of them has been implemented. For example, after the 2nd World War the ideaof constructing Lower Vistula Cascade (LVC) was prepared. It was to consist of 8 barrages,reservoirs and hydropower plants. The main purpose of the LVC was to produce energy andto create an inland navigable waterway connecting the central Poland with the harbor city ofGdansk. Unfortunately, finally only one barrage was developed in Wloclawek in 1970.At present, there is no long-term strategy for the development of the lower Vistula . Somepeople say that the Vistula is the only one wild, not regulated, natural river in Europe andshould remain in this state as it is. On the other hand, water specialists point out that it is theonly river of this size in Europe, that does not bring economic and social benefits to the country.The question of economic use of the lower Vistula River became particularly important becauseintensively developed the Port of Gdansk, located at the mouth of Vistula River, will soon needadditional connection in the form of waterway with the center of Poland. On the other hand,while discussion dealing with the Vistula River, usually only general opinions and arguments arepresented. It seems to the authors that it would be better if such discussions were supported atleast by the results of basic hydraulic analysis. To this order, the authors would like to presenttheir own (hydraulic) arguments to reactivate the barrage cascade project. Various aspects ofthe concept, such creation of the potential inland waterway, hydropower, flood control and waterretention, are discussed in the article.


258



The results of analysis allow to formulate the following general conclusion. Comprehensive useof various possibilities of the Lower Vistula is possible only due to the construction of the cas-cade of barrages, in which the dams are located in series along the river. The LVC is the onlytechnical solution that on the one hand enables comprehensive use of the potential of this sectionof the river and on the other hand limits the threats it generates.The results of analysis and conclusions presented by the authors were disseminated in Poland.In the years 2014-2017 they were presented to the local and national authorities as part of theseminars regarding the reactivation of inland waterways in Poland. It seems that they causedsome positive effects on the policy issues concerning the strategy for the Lower Vistula, sincerecently several important decisions dealing with the development of the Port of Gdansk andthe Lower Vistula River have been made by the Polish Authorities.

Keywords: Vistula River, Lower Vistula Cascade project, inland waterways, hydropower, flood

control, water retention

259


Reservoir sedimentation impact downstream in a semi-aridbasin with greenhouse cultivation

Sergio Arjona ∗† 1, Agustın Millares 2, Asuncion Baquerizo 2

1 Andalusian Regional Government – Spain2 Group of Environmental Fluid Dynamics, Andalusian Institute for Earth System Research -

University of Granada (IISTA) – Spain

Sedimentation is one of the major problems of reservoir management because determinethe useful life of these strategic infrastructures. Its role is not limited to guaranteeing waterreserves, but to regulating and controlling the impact of severe flooding, both of which arekey issues in semi-arid and Mediterranean environments. In these areas, the effects of erosiveprocesses upstream and the huge amount available sediment at the floodplains make fluvialcontributions especially important. This work analyzes the loss of storage, in a medium-termbasis, of Beninar reservoir (Almeria, Spain) built in a semi-arid watershed and its consequencesdownstream. The reservoir, in the Adra river basin (Southern Spain), was finished in 1983closing an area of approximately 522 km2 and providing a real maximum storage of 33 hm3for intensive agricultural demands. The coastal area of the basin harbors more than 28.000hectares of greenhouses, which have high demands for irrigation. Its construction was alsoplanned to prevent floods downstream as the 1973 extreme event, which highly affected thisarea. Bathymetric and topographic measurements have been carried out for the first time sinceits startup. Samples of sediment were taken upstream along the river and measurement offlow were registered for the whole period. The total sediment volume arrived to the reservoirduring the last 32 years was 6,8 hm3, of which 1,68 hm3 are estimated to come from fluvialcontributions. The results remark the torrential nature of rainfall events for generating largesediment contributions and highlights the importance of taking into account these types ofevents. During the studied period, three intense pulses of a few hours represented a 20% ofvolume loss of its total capacity. Specific models for torrential rivers were applied to estimatethe volume of sediments in the reservoir. Transports processes in immature debris flow conditionsexplain the volume of sediments by fluvial contributions. The total loss of storage is especiallyrelevant from two points of view; 1) reduction of flood abatement due to sedimentation andstructural problems of dam, which has left only 2 hm3 of regulation capacity and 2) loss of watervolume which is essential to improve the water quality of the overexploited and salinized aquiferswhich supply the greenhouses downstream. These two effects are contradictory and complicatethe future management tasks. Beninar reservoir is a key infrastructure to preserve a competitiveprice of water for the mayor industry in southern of Spain, which is greenhouse cultivation. Theobtained results question the viability of this productive model under the current conditions.This is especially true if we consider the predictions made for the IPCC climate change scenarios,that includes increases in the severity of events along the Mediterranean areas.

Keywords: Semiarid environments, sedimentation, greenhouses, water price.


260



Comparing of circular and square collars operation in reductionof local scour around bridge piers

Saeed-Reza Khodashenas ∗† 1

1 Water Engineering Department, Ferdowsi University of Mashhad, Mashhad – Iran

There are many reports about failure of bridges around the world due to scouring. Thisshows the importance of research on scouring in bridge design. Flow pattern and mechanism ofscouring around a bridge pier is very complex and has been reported by various investigators.Collars are used to prevent excessive scouring around bridge piers. Scouring around bridgepiers is one of the most important reasons of bridge destruction and causes to a great deal ofdamage every year and is defined as a natural phenomenon caused by the flow of water in riversand streams. Local scouring around the bridges pier occurs because of flow separation anddeveloping several vortexes around the bridge pier. Different methods have been proposed toprevent or reduce scouring around bridge piers for example riprap, submerged plates, slots, andcollars and so on. Generally scour reduction methods divide to two categories: direct methodsand indirect methods. The first methods use to increase the bed resistance and second methodsuse to change the flow pattern around the bridge piers. In this study operation of two types ofcircular and square collars has been investigated on a single cylindrical pier. The results showedthat using of these two types of collars cause to reduction of scour depth specially under thebed level (elevation). The square collar had a best operation in reduction of scour depth intothe circular collar (the square collar was more effective than circular shape in decreasing of thescour depth). The square and circular collars showed 70% and 50% decrease in rate of scourdepth, respectively in comprised with the unprotected pier.

Keywords: : Scouring, Collar, Bridge pier, Clear, water


261


Poster session P.C – Sediment and pollutant dynamics in rivers

Temporal variability of contaminated sediments in a stronglyregulated reservoir of the upper Rhine River

Germain Antoine ∗† 1,2, Thomas Pretet 3, Matthieu Secher 3, Anne Clutier 3

1 Laboratoire d’Hydraulique Saint-Venant –6 quai Watier, BP49, 78401 Chatou – France2 Laboratoire National Hydraulique Environnement (EDF LNHE) – 6 quai Watier, 78401 Chatou –

France3 Engineering Center for Hydraulics (EDF CIH) – Chambery – France

The upper Rhine River is a highly harnessed and regulated river. Its main channel is naviga-ble and its water is used for agriculture, drinking water supply and electricity production. EDF(a French electricity company) is in charge of eight dams on the upper Rhine River for producinghydro-electricity. In order to increase the safety and the competiveness of the installations, butalso to reduce their environmental impact, the sediment dynamic in these reservoirs has becomea key factor to control and predict. In this study, we focused on the Marckolsheim reservoir,which is located 50 kilometres upstream the city of Strasbourg. Since its construction in 1961,this reservoir has been filled continuously with cohesive sediments, partially contaminated.To keep the water level suitable for navigation, the dam is regulated with a high-frequencyrepositioning of its gates. This regulation, combined with the bifurcation configuration of thechannel, leads to a complex and unsteady hydrodynamic in the reservoir. Furthermore, thehigh temporal variations of suspended sediment supply makes the deposition in the reservoireven more difficult to predict. Two field campaigns were performed in 2015 and 2016 undertwo different discharge conditions, with the objectives of estimating hydraulic and suspendedsediment transport variables.The numerical codes TELEMAC-2D and SISYPHE (www.opentelemac.org) were used to sim-ulate in 2D (integrated along the water depth) the hydrodynamic and the suspended sedimenttransport on this site. A ten kilometres long model was built and calibrated with the measureddata of the 2015 and 2016 field campaigns, but also with measurements of sediment parametersthat have been done previously, like erosion tests (Westrich, 2010). The originality of this modelconsists in an explicit 3D representation of the dam gates. An algorithm was implemented inTELEMAC in order to adapt the gates position at each time step, in conformity with the realregulation rules followed by the dam operator. By using upstream measured data of dischargeand suspended sediment concentration as boundary conditions, a six months period was simu-lated. The comparison of the simulated results with bathymetric surveys shows good agreementsif specific properties of sediments related to settling processes are taken into account.Finally, the dynamics of the contaminated sediments has been simulated. The SISYPHE codehas been used for allowing the simulation of two cohesive sediment classes: one class for con-taminated sediments, one class for the non-contaminated ones. A 3D spatial distribution ofthe contaminated sediments in the reservoir has been defined at the initial state from in situmeasurements. The long-term simulation gives interesting highlights of the effect of flood eventson the resuspension conditions of the contaminated sediments.

Keywords: reservoir, morphodynamics, contaminated sediments, TELEMAC, MASCARET


262



Questions in the quantitative analysis of sediment load -example of three major rivers in Hungary

Eniko Anna Tamas ∗† 1, Johanna Ficsor 1

1 National University of Public Service, Faculty of Water Sciences (NUPS FWS) – 6500 Baja,Bajcsy-Zsilinszky u. 12-14. – Hungary

The importance of the monitoring of sediment processes is unquestionable: sediment balanceof regulated riverssuffered substantial alterations in the past century, affecting navigation, energy production, fishhabitats and floodplainecosystems alike. The changes in flood characteristics and rating curves of our riversare regularly being researched and described, involving state-of-the-art measurement methods,modeling tools andtraditional statistics. Sediment processes however, are much less known. Unlike the investiga-tion of flow processes,sediment-related research is scarce, which is partly due to the outdated methodology and poordatabase backgroundin the specific field. Sediment balance of the river Danube has changed drastically over thepast century. Sediment monitoring on the river Danube started as early as the end of the 19thcentury, with scattered measurements carried out. Regular sediment sampling was developed inthe first half of the 20th century all along the river, with different station density and monitoringfrequencies in different countries. Sampling frequency of suspended load is 3 to 7 per year inHungary, and even lower for the bed-load, not only on the Danube river but also on large tribu-taries like the Drava and the Tisza rivers. Data related to sediment quantity are unreliable andoften contradictory. It is difficult to produce high quality long-term databases that could supportand enable the mathematical calibration of sediment transport models. Sediment measurementsare different in different countries in Europe, thus engineers face a challenge to compare mea-surements on international rivers. The authors give a detailed analysis and overview of sedimentsampling methods, an inventory of the available datasets and data management in Hungary onthe rivers Danube, Drava and Tisza, aiming at the determination of quantitative changes insediment transport based on field data.

Keywords: sediment load, quantitative analysis, field data


263



Comparison of standardized methods for suspended solidconcentration measurements in river samples

Guillaume Dramais ∗ 1, Benoıt Camenen 1, Jerome Le Coz 1, Chloe Le Bescond 1,Fabien Thollet 1, Mickael Lagouy 1, Alexis Buffet 1, Celine Berni † 1

1 Irstea centre de Lyon-Villeurbanne, UR RiverLy, 5 rue de la Doua 69625 Villeurbanne cedex – France

SSC (Suspended Solid Concentration) measurements in rivers bring complex scientific issues.Many questions arise on the spatial and temporal distribution of particles throughout a cross-section, on the properties of particles like grain-size, and also on the sediment transport capacityof streams and rivers. In this study, we focused on the SSC and grain size distribution measuredfrom samples automatically or manually acquired in rivers. Many agencies suggested slightlydifferent methods for measuring SSC: The European standard NF EN 872, which related tothe US EPA 160.2 requires sub-sampling using shake-and-pour aliquot selection. The APHA2540D requires sub-sampling by pipetting at mid-depth in the original sample shaken with amagnetic stirrer. These methods lead to significant uncertainty when particles larger than 63µm are present in the samples. The ASTM D3977 analysis method, endorsed by the USGS ismore accurate to capture and quantify particles larger than 63 µm. In this study we evidencethe sub-sampling bias over a large concentration range using a set of samples from an Alpineriver.

Keywords: Suspended Solid Concentration (SSC), sand, NF EN 872 standard, sub sampling, sieving


264



Using high-resolution bedload transport tracer measurementsto investigate the characteristics of bedload transport over a

large urban flood event

Francesca Berteni ∗† 1, Benjamin Plumb 2, William Annable 2, Giovanna Grossi 1

1 Universita degli Studi di Brescia – Department of Civil, Environmental, Architectural Engineeringand Mathematics (DICATAM) – Italy

2 Department of Civil and Environmental Engineering, University of Waterloo – Canada

Many regions around the world have experienced an increased frequency of large magnitudeflood events arising from changing climate patterns. Beyond the overt flooding issues whichensue, changes to river dynamics and rates of channel change can also be profoundly affectedleading to compromised infrastructure and changes in aquatic habitat niches. Evaluation ofchannel change is often evaluated by employing sediment transport models as field data duringhigh magnitude low frequency events is rarely (if ever) available, however, transport rate esti-mates are heuristic at best to within 1 – 3 orders of magnitude with little ability to calibratenor validate results.Mimico Creek (66.3 km2) is an urban gravel-bed channel in southern Ontario, Canada that hasundergone intensive event-based sediment transport sampling (Helley-Smith) and inter-eventbed material particle tracking (embedded RFID tracking) over a three-year period between2011 and 2013 (Plumb et al, 2017). On July 8th, 2013 a precipitation event occurred generatinga flood in exceedance of the 100-year return period. Pre and post erosion surveys along a 2.1km reach combined with the sediment transport studies and a proximal hydrometric monitoringstation afforded a unique opportunity to evaluate the performance of various sediment transportmodels applicable to gravel-bed rivers for a short duration large magnitude low frequency event.A HEC-RAS model was developed of the study reach and calibrated to a series of dischargeevents where in-situ bedload sampling occurred. Both step-wise discharge and unsteady flowsimulations were evaluated to compare sediment transport rates for a range of transport modelswhich included the Meyer-Peter Muller (1948) and the Wilcock and Crowe (2003). In the caseof the highest magnitude flood events, the Wilcock and Crowe model more accurately portraiedthe bulk in-situ sediment transport rates of field observations. Fine-grain fractions were notablyoverestimated compared to field observations as floodplain storage of sediments was observed inthe field which could not be differentially accounted for in the transport model.A calibration curve was developed using the Wilcock and Crowe transport model to determinebed material transport rates as a function of reference shear stress and calibrated to observedtransport rates during the same flood events. Results from the modelling exercise found traveldistances compared relatively well against field observations and in some instances overestimatedtravel distances. Findings here identify the importance of accounting for clast interactions intransport estimates. The Wilcock and Crowe model accounts for bulk inter-particle interactionsand the armor layering effects which could not be accounted for using the Meyer-Peter M’ullerequation, which was not able to be correlated to the field conditions and bed material gradation.

Keywords: sediment transport, simulation, calibration, flow, HEC RAS


265


Poster session P.D – Fluid Mechanics and sediment processes

Hydraulic physical model production with ComputerNumerically Controlled (CNC) manufacturing techniques.

Pierre-Yves Henry ∗† 1, Jochen Aberle 1,2, Christy U. Navaratnam 1, Nils Ruther 1

1 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology(NTNU) – S.P. Andersens vei 5, 7491 Trondheim – Norway

2 Leichtweiß Insititute for Hydraulic Engineering and Water Resources, Technische UniversitatBraunschweig – Braunschweig – Germany

Physical scale models are a well-accepted tool in hydraulic engineering for the design of hy-draulic structures with complex boundary conditions. Most of the models used for this purposeare so called fixed-bed models without a movable bed as they are a natural choice when it comesto the design of hydraulic structures. So far, these models have been built by shaping the modelsurface using cement layers and/or using rather smooth materials to build hydraulic structuresusing information on required model elevations from cross-sectional profiles. Consequently, de-tails of the ”real surface” in-between the profiles are not necessarily correctly reproduced whichin turn induces a modification of the roughness features of the model compared to the proto-type. To achieve similitude between the model and the prototype, models must therefore oftenbe calibrated by altering the model surface roughness, for example by roughening or smoothingthe surface. This in turn may cause a different near bed flow pattern between the model andprototype which in turn may affect the hydraulic resistance. Therefore, such scale models areprone to laboratory and scale effects.These effects may be minimized using novel technologies for the construction of scale modelsallowing for the reconstructing of the 3D roughness features of prototypes. Examples for suchtechnologies are Computer Numerically Controlled (CNC) manufacturing techniques and bedcasting techniques, which are reviewed in this paper. Casting techniques are usually performingwell in the reproduction of surface characteristics at the 1:1 scale, but are limited to small pro-totype sizes and cannot be used for the construction of scaled models. CNC-based technologyhowever, such as 3D-printing and 3D-milling, are characterized by a greater versatility as theyare based on the handling of Digital Elevation Models (DEM) of the prototype. These cannowadays be easily obtained from laser scans, sonar scans or photogrammetric methods (e.g.Structure for Motion). Thus, CNC-milling or 3-D printing of models offers a wide range ofapplicability to reproduce fluvial or hydraulic structures at different spatial scales.As an example, the present paper details the protocols developed to ensure the correct repre-sentation of the complex rock-fractured geometry of a closed channel, obtained from TerrestrialLaser Scanners (alternatively from Remote Operated Vehicles underwater sonar scans). Thenovelty of this scaled model production is to implement optical accesses in a closed (pressur-ized) hydraulic model, to allow for Particle Image Velocimetry measurements with a minimumimpact of the reproduced roughness elements. The effectiveness of this production protocol isdiscussed in comparison to the conventional methods used for the construction scale model. Po-tential limitations are explored and discussed in the context of modelling the roughness effectson the flow regime.

Keywords: Hydraulic model, Computer Numerically Controlled, Rough bed flows, Scaling


266



Sediment properties in the fluvial and estuarine environmentsof the Mekong river

Hoang-Anh Le ∗† 1,2, Nicolas Gratiot 1, William Santini 3, Olivier Ribolzi 3, SandraSoares-Frazao 2, Eric Deleersnijder 2,4

1 Asian Research Center on Water (CARE-Rescif), Ho Chi Minh City University of Technology – BlockB7, 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City – Vietnam

2 Civil and Environmental Engineering, Institute of Mechanics, Materials and Civil Engineering(IMMC) & Earth and Life Institute (ELI), Universite Catholique de Louvain – Place du Levant 1,

B-1348 Louvain–la–Neuve – Belgium3 Geosciences Environnement, IRD, Universite Paul Sabatier – 14 Avenue Edouard Belin, 31400

Toulouse – France4 Delft University of Technology, Delft Institute of Applied Mathematics (DIAM) – Van Mourik

Broekmanweg 6, 2628XE Delft – The Netherlands

The Mekong river, located in Southeast Asia, is one of the largest rivers in the world. Itis facing serious problems related to sediment transport, e.g. the reduction of sediment volumesupply to the delta and estuary. This study focuses on the physical properties of suspendedparticles in the upstream fluvial section (Luang Prabang, Laos) and in the region of tidal in-fluence (Song Hau estuary, Vietnam). These sites are respectively the upper and lower limitsof the Lower Mekong River (LMR), which are experiencing contrasted transport modes. Themain objective of this study is to quantify the proportion of inert sand and of cohesive particlesin the water through comprehensive measurements of particle size, settling velocity and floc-culation in the water column. Two field campaigns were undertaken in the summer monsoonseason. The results point out the predominance of flocculi, with sizes of 18 ± 5 µm in the fluvialenvironment and 15 ± 5 µm in the estuary and the similarities in patterns, mixture of sand (12± 5 %) and mud (88 ± 5 %). They also provide a statistically representative set of suspendedparticle populations in the upstream and downstream regions that could be used for improvingnumerical models.

Keywords: Mekong, sediment, erosion, LISST, SCAF


267



2D numerical simulation of meander morphology

Md. Sarfaraz Banda 1, Stephan Niewerth 1, Jochen Aberle ∗† 1

1 Department of Hydraulic Engineering, Leichtweiß-Institute for Hydraulic Engineering and WaterResources (LWI) – TU Braunschweig, Beethovenstraße 51a, 38106 Braunschweig – Germany

This paper describes the application of the two-dimensional (2D) modelling approach im-plemented in the open-source code Delft3D for the simulation of morphological development ofa natural meandering river. A specific reach of the Dhaleshwari River (Bangladesh) for whichfield data has been available served as case study. The bed morphology and meander planformadjustment in the study area were simulated over a 10-year period considering a time-varyingdischarge scenario. The results showed that the 2D model was able to reproduce morphologicalcharacteristics such as scour depth, bank erosion and pool-riffle morphology, even though themodel showed some deficiencies to reproduce bankfull channel width and transverse bed slopes.Regarding the planimetric evolution, the planform parameters (i.e., meander belt width, mean-der wavelength and radius of curvature) confirmed that the model results are realistic and arein agreement with results reported in the literature.

Keywords: numerical simulation, meandering river, bed topography, planform geometry


268



Observation and analysis of long-periodic modes in an openchannel confluence with dominant tributary inflow

Laurent Schindfessel ∗ 1, Tom de Mulder † 1, Mia Loccufier 2

1 Hydraulics Laboratory, Dept. Civil Engineering, Ghent University, Belgium (UGent) – Belgium2 Dept. Electrical Energy, Metals, Mechanical Constructions & Systems, Ghent University – Belgium

Open channel confluences are the nodes of the hydraulic network: they determine the waterstages and the transport of sediment and solutes in the network.In a confluence, two shear layers can often be found: the so-called mixing layer between theincoming flows and a shear layer between the separation zone and the merging flows (Best,1985; Rhoads and Sukhodolov, 2008; Mignot et al., 2014; Guillen Ludena et al., 2017). Thelatter layer may be absent if no separation zone is formed, which can occur when the downstreamcorner allows a smooth turning of the tributary flow. In the vicinity of the shear layers, coherentstructures are formed by the velocity differences over the shear layers. Examples of such coherentstructures are vortices and helical cells (also called streamwise oriented vortical cells).Vortices can be shed in both shear layers and can be of two types: Kelvin-Helmholtz vorticeswith fixed rotational sense or wake vortices with alternating rotational sense.Helical cells appear in confluences because of the curvature of the flow (Rhoads and Kenworthy,1995). These cells transport fluid vertically and laterally. Constantinescu et al. (2012) discernedthat these helical cells can be subjected to large-scale oscillations, which are also influenced bythe discharge ratio.Schindfessel et al. (2015) noticed that an intermittent flow feature appears when the dischargeratio is small, i.e. when there is dominant tributary inflow. The intermittent flow feature hasa long return period and appears as alternating surface velocities in the downstream channel.At some instances in time, the flow in the confluence appears as expected based on conceptualmodels: the flow from the main channel is deflected by the tributary inflow as it enters theregion of flow contraction. At other instances in time, all particles that come from the mainchannel migrate to the right and coalesce in the mixing layer. This movement is driven by theupwelling of fluid near the right bank.For a deeper understanding of the latter phenomenon, the present contribution applies a modaldecomposition technique to the data, allowing to investigate the full spatial extent of the long-periodic oscillations.Experience with modal decomposition techniques revealed that a global Fourier decomposition(DFT) offers the best properties for the current purpose. Eddy resolving numerical simulationsare used to provide accurate and comprehensive velocity fields. In the numerical simulations,the sudden and large changes in the lateral velocity occur in the same area as measured inthe experiments, although the return period in the numerical simulations is smaller. Still, thenumerical results allow to use the DFT methodology to study this intermittency in the flowfeatures. Since the DFT is applied to instantaneous spatial fields, the resulting modes allowto discern the simultaneous velocity oscillations over the confluence area. Consequently, thespatial extent of the modes can be easily obtained, as well as possible interaction of differentflow features.The modal decomposition technique shows that the intermittent flow feature originates fromshifts in the height above the bed at which the tributary flow breaches into the main flow andat which it subsequently impinges on the opposite bank. Although the intermittent flow featurethus originates near the upstream junction corner, it has a considerable impact on the flow in


269



the downstream channel because of the presence of the opposing bank. The impinging of thetributary flow on this bank induces namely alternating helical flow in the downstream channel.This helical flow can form a means of sediment transport and can cause an increase in bed shear(Constantinescu et al., 2012). It is thus important to understand the intermittent flow featuresthat occur at dominant tributary inflow, something to which this paper contributes.

Keywords: Confluence, Hydrodynamics, Large Eddy Simulation, DFT

270


Numerical analysis of flood with a double grid model

Go Morikawa ∗† 1, Ichiro Kimura 2

1 Graduate School of Engneering, Hokkaido University – Japan2 Faculty of Engineering, University of Toyama – Japan

Heavy rains like Guerrilla rainstorms are observed recently in japan because of climatechange. Japanese rivers’ slopes are steeper and they are shorter than rivers in the world. There-fore, heavy rains sometimes cause huge floods in Japan. That is the reason why fast and accuratenumerical hydrodynamic models are needed. Nowadays, detailed information of the bathymetryis available due to improved measurement techniques. Bathymetric data with a very high spa-tial resolution of the order of magnitude of meters can be obtained. Generally, the results ofcomputations that use such bathymetric data become accurate. However, it is difficult to getsuch results at short computational time. My topic is about this problem. This study presentsa numerical hydrodynamic model for shallow water flow named Hyper Grid Model.Hyper Grid Model has two types of grids, which are a coarse computational grid and a fine gridcalled subgrid. A computational grid is a coarse grid that is composed of some subgrids. Thebed level and roughness can vary strongly over short distance, while water levels vary in space.Because of that principle, the bed level and roughness is defined on the subgrid cell and thewater level is assumed to be uniform within a computation-grid cell. Governing equations arediscretized on a coarse grid, but accounts for high-resolution bathymetry and roughness varia-tions on a subgrid. In this paper, it is shown that the results of the simulations computed byHyper Grid Model become as good as high-resolution results, but at much shorter computationaltime.Two examples are shown in this paper. Both examples assume flood of Toyohira River thatgoes through Sapporo. One example focuses on the area around the upstream of the river andthe other example focuses on the area around the downstream of the river. The former areais in mountains. We calculate the flood flow around the area by three models. One is HyperGrid Model, another model has only fine grids and the other has only coarse grids. I showthe results of three calculational models and compare the computational time of Hyper GridModel with the times of other two models. The other example considers the city center area ofSapporo. Therefore, this example assumes the building coverage ratio. Like the former example,we calculate the flood flow by those three models in this example and compare the results. Inaddition to this comparison, we compare an existing physical experimental result with the threecomputational results. The experiment was performed in 1999. Sapporo’ city was expressed bymany concrete bricks. The way to arrange the bricks depended on the Sapporo city planning.Through the computations in two different cases, it was shown that the present Hyper GridModel is a efficient computational tool to simulate large scale phenomena.

Keywords: numerical hydrodynamic models, climate change, bathymetry, flood, computational

time


271



COURLIS: a new sedimentology 1D module for MASCARET

Matthieu Secher ∗† 1, Philippe Ung 2,3, Eric Valette 1, Magali Jodeau 2, Nicole Goutal 2,4

1 Centre d’Ingenierie Hydraulique (EDF-CIH) – 15 avenue Lac du Bourget Passerelles Savoie Technolac73373 Bourget-du-Lac – France

2 Laboratoire National d’Hydraulique et d’Environnement, EDF R&D – 6 quai Watier, 78401 Chatoucedex – France

3 Mathematiques - Analyse, Probabilites, Modelisation - Orleans (MAPMO) – CNRS : UMR7349,Universite d’Orleans – B.P. 6759, 45067 Orleans cedex 2 – France

4 Laboratoire d’Hydraulique Saint-Venant – Ecole des Ponts ParisTech, EDF R&D, CEREMA – 6 quaiWatier, BP49, 78401 Chatou cedex – France

COURLIS is a 1D sedimentology module coupled with MASCARET, 1D hydraulic code ofthe TELEMAC-MASCARET open source system. The code has been developed by EDF formany years, mainly for suspension sediment transport. Recently, the need of a 1D bedload codehas been identified to model the long term evolution of rivers and reservoirs (several decades).After a benchmark of existing and available 1D codes, we chose to develop an efficient version ofCOURLIS which calculates bedload transport. New numerical schemes were implemented, someimprovements were done in the geometry evolution algorithms. In terms of performance androbustness, the best scheme implemented is a finite volume upwind/downwind scheme. Severalsolutions are implemented to reduce calculation time. All these developments are presented inthis paper.This new version of COURLIS for bedload sediment transport was validated successfully onseveral test-cases and the results of this validation are presented here (sediment aggradationsexperiment of Soni, sediment degradation experiment of Newton, dam break experiment of B.Spinewine and Y. Zech). A real case of a river with a reservoir has been simulated during an 11year period. These 11 years were reduced to 2 years after cutting flow rates lower than the sedi-ment incipient flow rate. The calculation time on this real case is very similar to those obtainedwith codes tested in the benchmark and the results are in a good agreement with measurementsand other code results.COURLIS (suspension and bedload sediment transport) will be released in the next version ofthe TELEMAC-MASCARET open source system and so, it will be freely available for sedimen-tology community. Further developments are planed like the implementation of several sedimenttransport formulas, the ability to simulate non-uniform sediment transport and a formulationto simulate the evolution of mixed bedrock-alluvial river.

Keywords: Sedimentology, Bedload, Numerical Scheme, Telemac, Mascaret, Courlis.


272



Experimental Studies on the Formation of Air-core inside theDrop Shaft

Dong-Sop Rhee ∗† 1, Hoje Seong 1, Inhwan Park 1, Hyung-Jun Kim 1

1 Korea Institute of Civil Engineering and Building Technology – South Korea

Urban inundation damage is increasing due to climate change and rapid urbanization. Theseurban environment change leads to the decrease of reservoir capacity of the river basin and thelack of drainage capacity in urban areas. Drainage pumping station and detention pond havebeen previously used to prevent flooding as major measures to secure drainage capacity inurban areas. Recently, however, the deep-underground tunnel and underground detention pondare emerging as the most effective flood prevention measures. In the aforementioned drainagesystems, the drop shaft, which is an inlet of the underground tunnel, has the greatest influenceon the discharging efficiency. Thus, it is important to understand the flow characteristics in thedrop shaft to increase the discharge efficiency. The vortex flow, which occurs at the intake ofthe drop shaft, flows along the wall of vertical shaft with air. The air-core in the drop shaftenhances the drainage efficiency by mitigating choking and sustaining flowing area. In this study,an experimental study on the air-core that discharges the air to prevent choking and maintaindischarge effect was carried out. The laboratory channel is consisted of the multi-stage spiralbasement inlet and the drop shaft with 10 cm diameter. Considering that the multi-stage spiralbasement inlet is a shape to improve the discharge effect by comparing the general inlet shape,it is an important to solve the reduction of the discharge effect by the choking in the drop shaft.In this laboratory channel, shape of the air-core in the drop shaft was measured for five inflowflow rates (0.0019 m3/s ˜ 0.0202 m3/s). As the inflow flow rate increased, the air-core size wasdecreased from 8.5 cm to 4.2 cm.

Keywords: Drop shaft, Air core, Choking, Discharging efficiency


273



Two-dimensional pollutant transport simulations in naturalstreams with horizontal recirculation zone

Inhwan Park ∗ 1, Hoje Seong 1, Hyung-Jun Kim 1, Dong-Sop Rhee † 1

1 Korea Institute of Civil Engineering and Building Technology – South Korea

In this study, flow and pollutant transport simulations were conducted in the tidal reachof the Han River where the horizontal recirculation zone induced by the tidal cycle causes thestorage effect. The flow analysis results show that the flow direction was repeatedly changed dueto the downstream water level and the horizontal recirculation zone was occurred at the pointwhere the flow direction was changed. Thus, the pollutant cloud was advected back and forth bythe periodically occurred reversal flow. The storage effects of the horizontal recirculation zonecause that the concentration-time curve shows oscillatory increasing patterns, and the retentiontime of pollutant cloud was also increased.

Keywords: horizontal recirculation zone, reversal flow, retention time, tail of concentration curves


274



A Well-balanced Finite Volume Scheme for Shallow WaterEquations with Porosity: Application to Modelling Flow

through Rigid Vegetation

Minh-Hoang Le ∗† 1, Virgile Dubos 2, Marina Oukacine 1, Nicole Goutal 3

1 Laboratoire d’Hydraulique Saint Venant – Ecole des Ponts ParisTech, EDF R & D – 6 quai Watier78401 Chatou – France

2 ANGE, INRIA, LJLL – Universite Pierre et Marie Curie - Paris VI – France3 LNHE EDF R&D – 6 Quai Watier Chatou – France

Strong interactions exist between flow dynamics and vegetation in open-channel. Depth-averaged shallow water equations can be used for such a study. However, explicit representationof vegetation can lead to very high resolution of the mesh since the vegetation is often modelledas vertical cylinders. Our work aims to study the ability of a single porosity-based shallowwater model for these applications. More attention on flux and source terms discretizations arerequired in order to archive the well-balancing and shock capturing properties. We present anew Godunov-type finite volume scheme based on a simple-wave approximation and compareit with some other methods in the literature. A first application with experimental data wasperformed.

Keywords: open channel flow, vegetation, drag force, porosity, finite volume scheme


275



Feature Tracking Velocimetry applied to AirborneMeasurement Data from Murg Creek

Liekai Cao ∗† 1, Volker Weitbrecht 2, Danxun Li 1, Martin Detert 2

1 Laboratory of Hydro Science and Engineering, Tsinghua University, CN-100084-Beijing – China2 Laboratory of Hydraulics, Hydrology and Glaciology VAW, ETH Zurich, CH-8093-Zurich –

Switzerland

A new image feature tracking velocimetry is presented and tested on airborne video dataavailable from a previous study at Murg Creek (Canton Thurgau, Switzerland). Here, the seededflow scenery had been recorded by an off-the-shelf action camera mounted to a low-cost quad-copter, and video frames were ortho-rectified to sizes of 4482×2240 px2 at a scale of 64 px/m. Thenew velocimetry approach is as follows: An adaptive Gaussian mixture model is used for videobackground subtraction. Then, scale-invariant keypoints on each remaining binary foregroundimage frame are determined by a feature detection algorithm, and corresponding feature pointsin subsequent frame pairs are matched using the iterative random sample consensus method.The related feature shifts in metric space divided by the video frame rate finally give the ve-locity vectors. The obtained velocimetry fields are compared with findings from both a particleimage velocimetry and particle tracking velocimetry analysis in terms of accuracy and neededcomputational power. Indication is given that the feature tracking algorithm presents slightlyless precise results, but clearly outperforms the other two in relation to computational power.Therefore, the new simplified method provides a high potential tool that may enable a futureway to real time surface velocity measurements obtained from unmanned airborne vehicles.

Keywords: feature tracking, surface flow velocity, image analysis, computer vision, field experi-

ments, UAV

∗Speaker†Corresponding author: clk [email protected]

276



Mesh Sensitivity of an LES model of a 3D sediment-drivengravity current

Joe Pelmard ∗ 1, Heide Friedrich † 1, Stuart Norris 1

1 University of Auckland (Faculty of Engineering) – Level 4, Faculty of Engineering Building20Symonds Street, City Campus Auckland – New Zealand

Turbidity currents are a subaqueous sediment gravity-driven flow, which takes the form ofan underwater avalanche. They are one of the most energetic geophysical flows on earth and,from an engineering point of view, may cause critical damage to underwater infrastructure.Optical and acoustical fluid dynamic measurement techniques provide accurate data of thecurrents’ structure, however the opaque nature of these currents prevents the acquisition ofdata from their interior without relying on intrusive experimental equipment. Consequently,computational fluid dynamics represents an attractive alternative method for gaining insightinto the inner turbulent structure of turbidity currents.In the case of high Reynolds number turbidity currents, Large Eddy Simulation (LES) is the mostpractical method that allows a detailed description of the turbulence while requiring achievablecomputational resources. As with any CFD model, the grid resolution of the model has animpact on the accuracy of the solution. However, few guidelines exist as to how to assess thequality of the resolution of a LES simulation. Consequently the choice of the grid resolution isusually left to the expertise of the user, and only few studies focus on the evaluation of the gridand the influence of refining on the filtered quantities and the turbulent statistics. Therefore,the goal of this work is to quantify the influence of the grid refinement on a LES simulationof a 3D sediment-driven Boussinesq gravity current using the standard Smagorinsky model,for a laboratory lock-exchange experiment. The simulations are made for a laboratory scaleconfiguration with a buoyant Reynolds number (Reb=Grˆ0,5) of 60000.Taking the finest mesh as the reference solution, the quality of the LES model is assessed byobserving the evolution of the turbulent statistics for each grid resolution. The spanwise two-point correlations are found to be the most useful parameters by showing the number of cells usedto represent the largest structures of turbulence and the density power spectrum are additionalyused to ensure that the cell size is small enough to have the LES filter cut-off wavelength insidethe inertial range of the turbulence spectra. From the observation of the vertical profiles of theratio of eddy viscosity to the molecular viscosity and the ratio of the subgrid scale shear-stressto the Reynolds shear-stress in the highly turbulent region following the head of the current,recommendations are eventually formulated to attain a well-resolved LES.

Keywords: sediment flow, turbidity current, lock exchange, grid resolution, Large Eddy Simulation,

LES


277



An Eulerian-Lagrangian numerical method to predict bubblyflows

Elli Mitrou ∗† 1, Bruno Fraga 2, Thorsten Stoesser 1

1 Cardiff School of Engineering [Cardiff] – Queens BuildingsThe ParadeCARDIFF CF24 3AAWales –United Kingdom

2 School of Mechanical and Civil Engineering, University of Birmingham (UoB) – Edgbaston,Birmingham B15 2TT – United Kingdom

Gas bubble plumes are widely used in environmental applications such as destratificationand aeration of lakes and reservoirs, ice prevention, accidental deep sea blowouts of gas, orgas leakage from natural vents. Crossflow is usually present in many of the aforementionedapplications. Lima Neto et al. (2007) reported a crossflow of 0.3m/sec for an aeration projectin the iced-covered Athabasca River, Canada. Although the effect of crossflows on single-phaseplumes and jets has been studied extensively, little is known about their effect on multi-phaseplumes. The understanding of the underlying physics of the interaction between the gas andliquid phases has been a challenging task for both Computational Fluid Dynamics modelers andexperimentalists.In this paper the refinements to an in-house large-eddy simulation (LES) based CFD code toallow its application to study bubbly flows are reported. The LES code Hydro3D solves thefiltered Navier-Stokes equations on a staggered grid for the continuous (liquid) phase and aLagrangian Particle Tracking algorithm is introduced which predicts accurately the dispersed(bubbles) phase. A two-way coupling approach is proposed, in which the exchange of informationis required twice: 1) the interfacial particle forces are calculated and the particles’ velocitiesobtained; 2) the contribution of the dispersed phase to the continuous phase is computed andadded as a source term to the liquid’s momentum equations. Both coupling processes areachieved by connecting randomly placed Lagrangian particles with fixed locations of the Eulerianframework and this is achieved through a mapping technique. The volume of fluid influenced bythe particle is defined with the PSI-cell technique: only the fluid nodes of the cells in which theLagrangian particle’s center is located receive the momentum source. The transfer of quantitiesbetween phases is done through the smoothed delta function developed by Yang et al. (2009).The model’s performance is assessed by predicting the hydrodynamics of a plume in crossflowfor which data from experiments conducted in Zachry Laboratory of the Department of CivilEngineering of Texas A&M University by Rezvani (2016) are available for model validation. Itis shown that the horizontal and vertical velocities obtained show a good agreement with theexperimental PIV measurements.

Keywords: Bubble plumes, LES, Eulerian, Lagrangian mapping


278



Modelling river hydro-sedimentary fluxes during a highmagnitude flood event

Jeremy Lepesqueur ∗† 1, Renaud Hostache 1, Nuria Martinez-Carreras 1, Cyrille Tailliez1, Christophe Hissler 1, Luc Manceau 2, Claire Delus 2, Benoit Loson 2, Emmanuelle

Montarges-Pelletier 3

1 Luxembourg Inst. Science & Technology – 41, rue du Brill, 4422 Belvaux – Luxembourg2 Univ. de Lorraine, LOTERR – Ile du Saulcy, CS60228, 57045 Metz cedex 01 – France

3 Lab. Interdisciplinaire Environ. Continentaux (LIEC) – 54500 Vandœuvre-les-Nancy – France

Extensive Metallurgical activities nearby river systems in Europe have been responsible overthe two past centuries for river system contaminations. In this context River Orne located ineastern France is suffering from sediment contamination due to the past metallurgical activities.Although recent water policies become more conservative, past contaminations due to industrialwastewater release still represent an issue. As a matter of fact, there is a need for monitoringand predicting the potential resuspension of persistent pollutants in rivers like Orne. In thisframework one objective of the project MOBISED (Modelling the reMobilization of SEDimentsand the release of associated contaminants https://www.list.lu/fr/projet/mobised/) is to imple-ment a 3D hydrodynamic model coupled with a morphodynamic model in order to evaluate thesediment transport and remobilization in a 4km long reach of river Orne during flood events.In this area of interest, the riverbed has an average width of 30 m and the river basin is drain-ing 1268 km2. Since 2014 maximum instantaneous discharges higher than 200 m3/s have beenrecorded. The modelled reach is composed of two large meanders. Its downstream boundary isequipped with a dam that contributes to the formation of mud banks due the deposition of thesuspended load as a result of reduced streamflow velocities. The stream bed is mainly composedof pebbles, coarse gravels and sand and only contains a small portion of silt. The river banksare mainly composed of a sandy mud mixture with a varying content of mud and is covered bydense vegetation. More locally, the river banks are made of concrete or silted up rockfill.Over the last two years, monitoring efforts have been concentrated on continuously recordingthe flow and the solid discharge, and more episodically measuring the bathymetry and the de-position of the sediment on selected banks.In this study the hydrodynamic code TELEMAC 3D (Hervouet et al., 2007) fully coupled withthe sediment transport module SISYPHE (Villaret, 2011) is forced by the flow at the upstreamboundary of the domain and by the water level at the downstream one. The unstructured meshis composed of 16492 nodes separated by distances in a range of 7m up to 25m.The standard version of SISYPHE does not allow for running simulations while mixing stratumtype, i.e. the user has to choose between three kinds of bed composition: i) non cohesive sedi-ment (up to 10 classes), ii) purely cohesive sediment (1 class), or iii) a mixture sand and mud(two classes). However this kind of representation does not fit for river Orne as the non cohesivesediment is characterized by a large range of particle sizes and as the cohesive sediment repre-sents a significant part of the sediment. Consequently, for the sake of an accurate representationof sediment transport over the domain SISYPHE has been further developed to allow for takingten classes of sediment into account regardless their type of stratum (cohesive or non-cohesivesediments). Indeed, through sediment mobility criterion and the sediment particle fall velocity,the erosion fluxes and the suspended load are related to the sediment diameter. This explainsalso why it is important to take into account a realistic granulometric distribution. The devel-opment of SYSIPHE allows then to simulate solid discharges for the 10 classes of sediments.


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The proposed SYSIPHE developments are discussed and evaluated based on the comparisonwith the standard version of SISYPHE. The necessity of including new development to take intoaccount the process of flocculation is also argued due to the impossibility to correctly representthe signal of turbidity in absence of sufficient current velocity for suspended load advection.

Keywords: TELEMAC, SISYPHE, sediment, river, flood

280


Numerical simulations on mixing of passive scalars in riverconfluences

Sebastien Pouchoulin ∗† 1, Emmanuel Mignot 1, Nicolas Riviere 1, Jerome Le Coz 2

1 Laboratoire de Mecanique des Fluides et d’Acoustique (LMFA) – CNRS : UMR5509, Univ. C.Bernard - Lyon I , Ecole Centrale Lyon, INSA Lyon – 36 Av Guy de Collongue 69134 Ecully cedex –

France2 Irstea centre de Lyon-Villeurbanne, UR RiverLy – 5 rue de la Doua Villeurbanne – France

The study deals with the mixing of passive scalars (as pollutants) in open-channel conflu-ences when both inflows exhibit different concentration of a given scalar. This is an importantenvironmental engineering issue as confluences on the one hand can play a major role on thescalar mixing and on the other hand are present in sewer networks, in street networks duringurban flooding and in river confluences. The dispersion of such passive scalars is investigatedtrough the analyses of the processes enhancing the mixing in the confluence and the obtainingof the length for complete mixing Lm and turbulent diffusion coefficient. The aim of this studyis then to establish a correlation between the length for complete mixing Lm and the confluencefeatures characterized by 1 geometric parameter: the angle of the confluence and 2 hydrody-namic parameters: the momentum ratio M* and the shallowness h/b.The flows in the confluences were numerically simulated by RANS calculations coupled with theadvection-diffusion equation at field scale, i.e. with Reynolds and Froude numbers correspondingto real rivers (Re = 1E7 and Fr=0.1). The roles of other parameters such as bed discordance,Reynolds and Froude numbers, bed forms... are not addressed here.

The numercial results highlight that mixing in the confluence and the corresponding down-stream branch is enhanced by the presence of secondary currents. However, the results showthat the concept of rapid mixing is somehow subjective as it depends on the criterion considered:length of complete mixing Lm or turbulent diffusion coefficient.The results aim at getting an operative empirical law linking the geometric and hydrodynamicparameters of the confluence with Lm. This empirical law would be used afterwards for acomplete hydrodynamic model of the Rhone basin, allowing to know how far away from theconfluence the two upstream rivers can be considered as completely mixed.

Keywords: mixing, CFD, confluence, passive scalar, pollutant


281



An enhanced depth-integrated model for flows over a negativestep with hydraulic jump

Tatsuhiko Uchida ∗† 1

1 Hiroshima University (HU) – 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527 – Japan

The negative steps can be seen in rivers around several structures such as weirs, groundsills,bed protection works and revetment works. Because the river bed downstream from the nega-tive step is prone to be scoured and eroded, it is important for designing river structures andthose maintenances to clarify flows over negative steps. Depth-integrated models have played animportant role of predicting flows for several practical problems. Because non-hydrostatic threedimensional models are too expensive to be applied to practical river problems with large scalephenomenon, there are many contributions to develop enhanced depth-integrated models to havethe ability of evaluating vertical flow structures. Those include secondary flow models and quasi-three dimensional models to evaluate velocity distribution and sediment transport for curvedand meandering channel. Recently, the authors developed the general bottom velocity compu-tation (GBVC) method [1] which is a non-hydrostatic depth integrated model to calculate threedimensional flow and sediment transport based on the three dimensional vortex motions aroundstructures and compound meandering channels within the framework of the two-dimensionalmodel. The GBVC4-DWL method [2] is the sophisticated model without assuming equilibriumbottom boundary conditions but with employing dynamic wall law (DWL) to calculate com-plex flow patterns near the bed induced by the presence of submerged obstacles. However, itis still challenging for the depth integrated models to calculate flows over negative steps ac-companying hydraulic jumps, because separation zone behind the step and the pattern of thehydraulic jumps depend on the several hydraulic conditions such as Froude number, step heightand downstream water depth. In this study, assuming the case in which the bed is covered withrelatively large roughness, an enhanced depth integrated model is developed to calculate varioushydraulic jump patterns generated downstream from the negative step. The present method isbased on GBVC4-DWL. The model with the virtual bed slope behind the negative step andthe critical slope of wave breaking is validated through the comparisons with the experimentalresults. Then the effects of equations and terms which compose the present method on the flowstructures downstream of the negative step are investigated by comparing the present methodwith several simplified calculation models from GBVC4-DWL including GBVC3 (equilibriumwall law model), SBVC3 (hydrostatic model) and 1DC (pure one dimensional model withoutconsidering vertical velocity and pressure distributions). The comparison shows the role ofvelocity distribution varied with vorticity production and non-hydrostatic pressure distribution.

Keywords: depth integrated model, nonhydrostatic, boundary layer, hydraulic jump, separation


282



Comparison of large woody debris prototypes in a large scalenon-flume physical model

Brian Perry ∗† 1, Colin Rennie 1, Andrew Cornett 1,2, Paul Knox 2

1 University of Ottawa – 75 Laurier Avenue East, Ottawa, ON K1N 6N5 – Canada2 National Research Council of Canada (NRC) – 1200 Montreal Road, Building M-58, Ottawa, Ontario

K1A 0R6 – Canada

Due to excessive rainfall in June of 2013, several rivers located in and near the City ofCalgary, Canada experienced significant flooding events. These events caused severe damage toinfrastructure throughout the city, precipitating a renewed interest in flood control and mitiga-tion strategies for the area. A major potential strategy involves partial diversion of Elbow Riverflood water to the proposed Springbank Off-Stream Storage Reservoir. A large scale physicalmodel study was conducted to optimize and validate the design of a portion of the new project.The goals of the physical model were to investigate diversion system behaviors such as flow rates,water levels, sediment transport and, debris accumulation, and optimize the design of new flowcontrol structures to be constructed on the Elbow River. In order to accurately represent thebehavior of debris within the system due to flooding, large woody debris created from naturalsources was utilized in physical model and its performance was compared to that of debris ofthe same size fabricated from pressed cylindrical wood dowels. In addition to comparing theperformance of these two debris types, the impact of root wads on debris damming was also in-vestigated. Significant differences in damming behavior was shown to exist between the naturaldebris and the fabricated debris, while the impact of root wad on damming affected the damstructure and formation. The results of this experiment indicate that natural debris is preferredfor studies involving debris accumulation.

Keywords: Large Woody Debris (LWD), Physical Model, River System, Debris Accumulation,

Flooding


283



The spillway design for the dam’s height over 300 meters

Yao Wei ∗† 1, Yuansheng Chen 2, Xiaobin Li 1, Xiaoyi Ma 3

1 Powerchina Guiyang Engineering Corporation Limited, Guizhou 550081 – China 2 Key Laboratory of

Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, China

Academy of Sciences, Beijing, 100101 – China 3 College of Water Resources and Architectural

Engineering, Northwest A &F University, Yangling, Shaanxi 712100 – China

According the current hydropower development plan in China, number of hydraulic powerplants with height over 300 meters will be built in the western region of China. These hydraulicpower plants would be in crucial situation with the problems of high water head, huge dischargeand narrow riverbed. Spillway is the most common structure in power plant which is used todrainage and flood release. According to the previous research, the velocity would be reachingto 55 m/s and the discharge can reach to 300 m3/s.m during spillway operation in the damheight over 300 m. The high velocity and discharge in the spillway may have the problems suchas atomization nearby, slides on the side slope and river bank, Vibration on the pier, hydraulicjump, cavitation and the negative pressure on the spill way surface. All these problems maycause great disasters for both project and society. This paper proposes a novel method for floodrelease on high water head spillway which is named Rumei hydropower spillway located in thewestern region of China. This paper has following components: Determining the type and thelayout of the spillway through the perspectives of air entrainment, flow jet angle and waterenergy dissipation in flushing pond structure. The physical hydraulic model has been used toevaluate spillway design effects.

Keywords: Energy dissipation, high flow velocity, atomization, Rumei hydropower spillway


284



Inferring thermal turbulent structures properties in the wake ofan array cylindrical obstacles

Saad Mulahasan ∗† 1

1 PhD, Department of Civil Engineering, College of Engineering, Al-Mustansiriyah University, Baghdad– Iraq

In this study a thermal camera was used to inferring the properties of thermal turbulentstructures at the water surface of an array of emergent vertical cylindrical obstacles locatedat one side of an open channel flow. Three different rod sizes of 1.25 cm, 2.5 cm and 5.0 cmwere tested. A thermal camera was used to record a series of snapshots of the water surfacetemperature distribution in the wake of the staggered cylinders at section where the flow wasconsidered to be uniform and fully developed. The most suitable place of eddies in the wakeregion was chosen after watching recorded video of each rod size experiment. The ideal locationis in the interface between the undisturbed cold water and the warm water flow.The zone shouldbe close enough to the seeding (hot water) point so that the mixing is not too high and thetemperature gradients too dissipated, but also far enough so that the eddies have space todevelop and have passed through some rods already. Temperature values were extracted foreach sequence at five selection points in the wake region using Matlab software. Time seriesof temperature for the snapshots of the five selected points in the area of eddy formation weredrawn. The results showed successive peaks with a slope of -5/3. The energy of the eddies wereextracted using Fourier transforms. Evaluation of the eddies in the wake of the rods for theexperiments, shows that the energy of the eddies is small at high frequency and large eddieswere found at low frequencies.

Keywords: Thermal structures, open channel flow, statistical analysis.

∗Speaker†Corresponding author: irrigation [email protected]

285



Non-intrusive techniques to measure roll waves level evolving ina flume.

Geraldo Maciel ∗† 1, Evandro Da Cunha 1, Yuri Sao 1, Andre Toniati 1, GuilhermeFiorot 2, Fabiana Ferreira 3, Claudio Kitano 1, Vicente Goncalves Junior 1

1 Universidade Estadual Paulista - Faculdade de Engenharia de Ilha Solteira - FEIS (UNESP) –Avenida Brasil, 56, Centro, 15385-000 - Ilha Solteira, SP – Brazil

2 Centro Universitario da Fundacao Educacional de Barretos (UNIFEB) – Av. Prof. Roberto FradeMonte, 389, 14783-226 - Barretos, SP – Brazil

3 Universidade Federal de Sao Paulo - Campus de Diadema (UNIFESP) – Rua Sao Nicolau, 210,Jardim Pitangueira, 09913-030 - Diadema, SP – Brazil

An open-channel experimental set-up is presented in this paper as a tool for examining thepresence of instabilities on free-surfaces flows of non-Newtonian fluid. When these flows occurin favorable conditions of inclination, discharge and rheological properties, the propagation ofinstabilities can evolve into a specific type of wave, known as roll waves. The experimentalapparatus developed allows study of stabilized roll waves in many scenarios for non-Newtonianrheology fluids, thereby constituting a highly useful tool for the understanding and control ofroll waves. The test fluid used in the experiments was carbopol gel which is rheometrically rep-resentative of the muddy material from natural disasters, such as mudflows. Two non-intrusivelevel measurement systems are proposed (ultrasonic transducer and laser-based absorption tech-nique), and the efficiency of each technique is presented and discussed. Both methods presentedrelatively low-cost implementation, and calibration procedure assured the quality of the results.The results from the experimental set-up were in agreement in shape and amplitude.

Keywords: roll waves, non Newtonian fluid, measurement methods, ultrasonic technique, light

absorption technique.


286


Poster session P.E – Extreme events

Sediment pulses and extreme events: assessing the effect ofstorm characteristics on propagation dynamics

Celso Castro-Bolinaga ∗† 1, Panayiotis Diplas 2, Robert Bodnar 3

1 North Carolina State University – United States2 Lehigh University – United States

3 Virginia Tech – United States

The objective of this research is to assess the effect that extreme hydrologic events have onthe propagation of sediment pulses in river corridors. These sediment-flow hazards are associ-ated with large amounts of loose material suddenly deposited in rivers by the action of externalfactors or processes of natural or anthropogenic origin, including landslides, debris flows fromtributaries, dam removal projects, and mining-related activities. Their occurrence is associatedwith severe channel aggradation and degradation, floodplain deposition, damage of infrastruc-ture, and impairment of riparian and aquatic ecosystems. Given that the intensity of rainfallevents have been significantly enhanced due to the influence of various human activities, sedi-ment pulses are expected to become more common, with a more pronounced downstream impactas such climatic changes directly affect the magnitude, duration, and frequency of flows in river-ine environments. Herein, numerical simulations were performed to characterize the propagationof a fine-grained sediment pulse for the 10-, 100-, and 500-yr storms. Results indicate that mag-nitude, frequency, and duration of the storms primarily influence the temporal variation of thetotal sediment discharge. In particular, these storm characteristics have a marked impact onthe relationship between pre- and post-pulse conditions in the river channel, the dissipation ofthe pulse peak discharge, and the travel time of the pulse apex.

Keywords: Alluvial Rivers, FineGrained, Flooding, Sediment Pulse


287



A comparative analysis of 3-D representations of urban floodinundation in virtual environments for hazard communication

purpose

Rosa de Santis1 ∗† , Francesco Macchione1 , Pierfranco Costabile1 , Carmelina Costanzo1

1 LaMPIT (Laboratorio di Modellistica numerica per la Protezione Idraulica del Territorio) -Environmental and Chemical Engineering – University of Calabria, Rende – Italy

The flood hazard/risk maps do not allow a non-expert audience an immediate perceptionof the flooding impacts. Therefore, we need to modernize maps providing new communicationapproaches. In this context, 3-D representations of flood inundation through emerging formatsin virtual and augmented realities may be considered as a powerful tool to engage users withflood hazards.The challenge of the research is to create a virtual 3-D environment aimed at supporting thepublic, practitioners and decision-makers in interpreting and understanding the impact of simu-lated flood hazards. For this purpose, the paper aims to perform a comparative analysis of twotechniques to carry out the 3-D realistic visualizations of a flood map for representing a poten-tial flooding of the Crati River, in the old town of Cosenza (South of Italy). The first approachdevelops a simple and quick workflow that provides an overall look at a neighbourhood level,but reveals some limits in water level visualization at the individual buildings scale. The secondone requires additional terrestrial laser scanning (TLS) acquisition and overcomes some limitsof the first approach, by providing a visual insight about water level close to building facades.

Keywords: 3D virtual environment, flood risk communication, 2D numerical modeling, shallow

water equation


288



Flood forecasting using a coupled hydrological and hydraulicmodel (based on FVM) and high-resolution meteorological

model

Marcos Sanz-Ramos ∗† 1, Arnau Amengual 2, Ernest Blade 1, Romu Romero 2, HeleneRoux 3

1 Flumen Institute (UPC) – B0 building, S-105, C/Jordi Girona, 1-3 08034 – Barcelona – Spain2 Grup de Meteorologia - Universitat de les Illes Balears – Spain

3 Institut de Mecanique des Fluides de Toulouse (IMFT) – INPT – France

The characterization and quantification of the runoff based on rainfall-runoff modelling iscrucial for flood risk assessment and in flood risk management plans. In recent years therehas been a fast development of hydrological numerical tools. The improvements have been inthe data (DTM, land uses databases, rain in raster format...) but also on the equations andnumerical methods used. Today two-dimensional shallow water models are increasingly used inthe computation of overland flow and rainfall-runoff transformation.In a parallel way, weather forecast models are capable to provide rain rainfall forecasts atconvective-scale of future events up to 96-h in advance. This kind of predictions can be analysedand used in flood warning systems and civil protection. For that purpose, three steps aretraditionally performed: 1) a meteorological simulations to achieve quantitative precipitationforecast (QPFs), 2) a hydrological simulation to obtain the runoff and 3) a hydraulic simulationto determine the maps of hazard and risk.In this context, a coupled two-dimensional distributed hydrological and hydraulic model wasdeveloped on the basis of Iber (Blade et al., 2014), a previously existing model. Iber solvesthe full 2D Shallow Water Equations (SWE) using the Finite Volume Method (FVM) basedon Roe scheme (1986). The model has been enhanced to be used as a hydrological model byadding the precipitation and losses processes as new source terms (rain, and losses) on the massconservation equation. Moreover, the new DHD scheme (Cea and Blade, 2015) was implementedin order to solve more efficiently and properly the SWE. Presently Iber allows to calculate in acoupled way rainfall-runoff (hydrological) and inundation (hydraulic) processes.The model has been implemented and calibrated with precipitation and discharge data in orderto simulate flood events in the La Muga basin (northeast of the Iberian Peninsula), within theEuropean project ”Flood Risk Assessment and Management in the Pyrenees – MediterraneanEuroregion” (PGRI-EPM). The study area is focussed on the upper part of the basin, whichis regulated by a dam (61 hm3 with three gates). The main purpose of the project was todevelop a method to optimize the management of flood scenarios in order to minimize the riskwhile maximizing the water resources. An accurate simulation of the rainfall-runoff processes,taking into account the dam is therefore needed. For that purpose, a coupled hydrological andhydraulic modelling was built.The Manning roughness coefficients and losses method (SCS) were calibrated using observationsof water level in the Boadella Reservoir, rain field data and one meteorological radar (doublecalibration).Once calibrated, the model was feed with the QPFs in order to reproduce some selected events.The hourly meteorological forecasts were provided by the WRF model as rain intensity rasterdata (Skamarock et al. 2008).The analysed events lasted from 2 to 5 days, and the computation time varied from 1.5 to 4 hours.This time is short enough for real-time decisions-making for the dam management, allowing to


289



compare some different dam operations and, in the case that a properly dam management cannotbe performed, warn to the population.This work has been partially funded by the Pyrenees – Mediterranean Euroregion under thePGRI-EPM Project, under the call ”Water Resources – Risk Management (Floods, Droughts,Submersion)”. More info at http://pgri-epm.eu/.

Keywords: Flood forecasting, Floog management, hydrologic, hydraulic simulation, SWE

290


Flood mitigation through riparian detention in response toclimate variability – a case study in Taiwan

Kwan-Tun Lee ∗† 1, Pin-Chun Huang 2

1 Center of Excellence for Ocean Engineering, National Taiwan Ocean University (NTOU) – No. 2,Peining Road, Keelung – Taiwan

2 Dept. of River & Harbor Engrg., National Taiwan Ocean University (NTOU) – No. 2, Peining Road,Keelung – Taiwan

Considering that urban areas may suffer more substantial losses than riparian farmlandsduring floods, diverting floodwater into riparian areas for temporal detention is expected tomitigate flood damage in downstream urban areas. In this study, an assessment has beenconducted to evaluate the effect of flood mitigation through riparian detention in response toclimate variability in the Tou-Chien Basin of Taiwan. A couple 1D-2D model was used tosimulate the flood wave transporting in the mainstream and the overbank flow inundating intothe urban areas. Based on the numerical simulation results, flooding extent and inundated waterdepth corresponding to different return periods with current flood prevention infrastructureswere detailed investigated. Various riparian detention strategies were proposed to alleviatesevere losses in the downstream urban areas of the Tou-Chien Basin.

Keywords: Flood detention, climate variability, unsteady flow, channel routing


291



Combined influence of terrain modell and roughness in dambreak wave simulation

Antje Bornschein ∗† 1

1 Technische Universitat Dresden (TU Dresden) – Institute for Water Engineering and AppliedHydromechanics 01062 Dresden – Germany

Dam break wave calculation provides data for disaster management as well as inundationarea mapping. During the last decade, high-resolution terrain data became available to establish2D hydrodynamic models. Manning‘s roughness is an important parameter within these modelsalthough its model conception is far older.The paper presents simulations which cover river valleys downstream of dams in Germany.These dams are mainly situated in the low mountain ranges, the valley bottoms are coveredwith forests. Meadows or fields are less common. But there are business areas and urban areastoo. That’s why experiences from other dam break inundation studies regarding historical dambreak failures are not well applicable because they have dealt with very steep and narrow valleysor valleys without vegetation.

After choosing Manning’s n values, a hydrodynamic model has to be calibrated and validated.In dam break inundation studies considering real events, this was done mainly with regard tothe arrival time. But no calibration is possible for prediction models considering hypotheticaldam failure scenarios. The calculation results of these models can only be evaluated using acomparison between different hydrodynamic models of the same valley reach or by means of sen-sitivity analysis considering roughness parameter or characteristics of the hydrodynamic modellike cell size or different wave approaches.In order to assess the combined influence of the terrain model as well as its representation in ahydrodynamic model and of the roughness parameter on the dam break wave calculation resultsdifferent hydrodynamic model sets of the same river reach are compared:- a 1D and a 2D-hydrodynamic model of a 59 km long river reach downstream of dam 1- two different 2D-hydrodynamic models (HEC-RAS, Hydro AS-2D) of a 24 km long river reachdownstream of dam 2- A sensitivity analysis regarding different Manning’s values was conducted for a river reachbelow dam 3

Keywords: dam break, hydrodynamic modeling, flood arrival time


292



Flood risk mapping for emergency management by applyinggrid-based model

Kun-Yeun Han ∗† 1, Jun-Hyung Park 2, Hehun Choi 3

1 Kyungpook National University – South Korea2 National Civil Defense and Disaster Management Training Institute – South Korea

3 Ministry of Interior and Safety – South Korea

A grid-based numerical model is developed by improving the diffusion hydrodynamic modelthat can accurately reflect LiDAR data and enable an efficient hydraulic analysis by linking riverand drainage networks. In order to verify 2D model, recent flood events, which occurred in theGimcheon area during Typhoon Rusa on 2002 is considered. For the estimations of flood disastervulnerability index, population density, household income, access to evacuation route/time, andshelter information are included. The flood hazard map considering flood depth, velocity, floodarrival time is combined with the flood vulnerability information to derive a flood risk map.The flood risk map presented in this study can provide useful information for the preparationof evacuation plan through accurate flood hazard results and disaster vulnerability index.

Keywords: Emergency Management, Urban Flood, Flood Risk Mapping


293



Flood hazard mapping techniques with LiDAR in the absence ofriver bathymetry data

Guenole Chone ∗ 1, Pascale Biron † 1, Thomas Buffin-Belanger 2

1Departement de geographie, d’environnement et d’urbanisme, Universite Concordia – Montreal, QC –Canada

2 Departement de biologie, chimie et geographie, Universite du Quebec a Rimouski (UQAR) – Canada

With both extreme precipitation events likely to occur more frequently due to climate changeand watershed anthropisation likely to increase peak floods, it is essential that areas at risk offlooding be well documented and frequently reevaluated. While this is the case in Europefollowing the EU Floods Directive, there are still large portions of the world, including Canada,where this information is either out of date or completely lacking. In Quebec (Canada), oneof the challenges is the very large territory, with very few datasets on river bathymetry, whichare required to run hydraulic models. The objective of this study is to assess the precisionand accuracy of flood hydraulic modelling exclusively using LiDAR elevation data that do notgenerally provide information on in-channel river bathymetry. Two different techniques weredeveloped to simulate flood levels, extents and depths. Both techniques start by assessing thelongitudinal profile of the water level in the channel from the LiDAR data. The dischargecorrection technique (DCT) consists of using this water surface profile as the river bathymetryand then subtracting the discharge corresponding to the LiDAR survey from the input flooddischarge of the model in order to compensate for the missing bathymetry. The terrain correctiontechnique (TCT) combines the longitudinal profile of the water surface with information onthe river discharge during the LiDAR survey to determine, using a 1D model (HEC-RAS),the corresponding flow depth, assuming a rectangular channel shape. This flow depth is thensubtracted from the LiDAR water surface elevation to create an estimated river bathymetry.Using both techniques, 2D hydraulic simulations are carried out (HEC-RAS 5.0), for dischargesof 20-, 100- and 500-years recurrence intervals. Both approaches were tested in two riversof Quebec (Canada) for reaches of several kilometers. The accuracy of the two techniques isassessed by comparing the DCT and TCT simulation results with simulations made with realriver bathymetry from detailed field survey. Sensitivity analyses were also conducted to assessthe impacts of flow conditions at the time of acquisition of LiDAR data, errors on channelManning’s n as well as errors on water stage assessment. Results show that flood stage can beobtained with very high precision (within a few centimeters) and reasonable accuracy (within afew tens of centimeters) with both techniques. The TCT is recommended as it is less sensitiveto flow conditions at the time of acquisition of LiDAR data and errors is Manning’s n, andprovides more accurate results. If calibration data are available, both TCT and DCT results insimilar flood levels, with a small error (less than 0.08 m). Bathymetry data thus provide littleinformation in these cases, indicating that expensive field work campaigns to obtain such datacan be avoided at the cost of only minor imprecision.

Keywords: Floods, LiDAR, Mapping, Hydaulic modeling


294



Flood management at narrow river mouth

Omar Seleem ∗† 1, Akihiro Kadota 1, Pratiwi Aziz 1

1 Ehime University – Japan

Hiji River is characterized by many tributaries, low bed gradient, and narrow river mouth.Due to these characteristics, several floods occurred in the past. The narrow river mouth isthe main reason of flood occurrence in Hiji River. The current study is focusing on the rainfallevent which caused massive damage in 2004. The purpose of the current study is to update theexisting hazardous map and compare the simulation results obtained from International RiverInterface Cooperative (iRIC) with the measured data to calibrate the model. The simulationwas carried out using Nays2DH within the measured data record from Japan Ministry of Land,Infrastructure, and Transport. The analysis result was compared with the inundated areas andalmost have the same results.

Keywords: Flood Control Management, Narrow River Mouth, Simulation, Hazardous Map

∗Speaker†Corresponding author: omar [email protected]

295


Author Index

Abad, Jorge, 167Aberle, Jochen, 103, 205, 266, 268Abily, Morgan, 156Abraham, David, 198Ait Elabas, Amine, 165Akutina, Yulia, 15Albayrak, Ismail, 206Aleixo, Rui, 49, 82, 248Ali, Sk Zeeshan, 51, 78Alliau, Damien, 145Altinakar, Mustafa, 33Alves, Elsa, 85Amann, Finn, 156Amel, Soualmia, 41Amengual, Arnau, 289Ancey, Christophe, 80, 219Annable, William, 265Ansari, Saber, 199Antoine, Germain, 36, 40, 145, 262Archambeau, Pierre, 134, 155Arjona, Sergio, 46, 260Arnaud, Fanny, 105Arnaud-Fassetta, Gilles, 125Arnez-Ferrel, Kattia-Rubi, 212Arseneault, Dominique, 74Ata, Riadh, 119Auel, Christian, 206Aufleger, Markus, 91, 111Aziz, Pratiwi, 295

Baar, Anne, 35Badoux, Alexandre, 150Balachandar, Ram, 142, 162Ballio, Francesco, 172Banda, Md. Sarfaraz, 268Baquerizo, Asuncion, 46, 260Barron, Jean-Dominique, 16Beche, Leah, 232Beckers, Felix, 122, 144Beheshti, Ali-Asghar, 22Bel, Coraline, 143

Belaud, Gilles, 41

Belleville, Arnaud, 110

Bellot, Herve, 143, 174

Benmamar, Saadia, 133

Bento, Ana-Margarida, 117

Berends, Koen, 88

Berni, Celine, 37, 50, 171, 264

Berteni, Francesca, 265

Bertin, Stephane, 194

Bickel, Alexander, 192

Biegert, Edward, 197

Bigillon, Francoise, 66

Billi, Paolo, 34

Biron, Pascale, 186, 294

Blade, Ernest, 289

Blom, Astrid, 216, 247

Blothe, Jan, 48

Bodmer, Pascal, 185

Bodnar, Robert, 287

Boechat Albernaz, Marcio, 35

Boersema, Matthijs, 67

Boes, Robert M., 100, 206, 243

Bohorquez, Patricio, 80, 218, 219

Boivin, Maxime, 74

Bonamy, Cyrille, 56

Bonilla Porras, Jose, 213

Bor Turkben, Asli, 255

Bornschein, Antje, 292

Bousmar, Didier, 64, 70

Box, Walter, 42

Branß, Till, 103

Brewer, Shannon, 166

Brousse, Guillaume, 125

Brufau, Pilar, 30, 99

Bruwier, Martin, 134, 155

Buffet, Alexis, 37, 264

Buffin-Belanger, Thomas, 74, 186, 294

Buldakov, Eugeny, 131

Burkli, Livia, 71

Byishimo, Protogene, 81

297

Cable, Joanne, 62Cagninei, Andrea, 69Calvani, Giulio, 43Camenen, Benoıt, 37, 171, 226, 264Cameron, Stuart, 160Camporeale, Carlo, 239Canada-Pereira, Pablo, 218Cao, Liekai, 276Carbonari, Costanza, 195Cardoso, Antonio, 83Carvalho, Elsa, 248Carvalho, Luıs, 248Cassan, Ludovic, 41, 244Castro-Bolinaga, Celso, 287Cazilhac, Marine, 47Cazin, Sebastien, 16Chagot, Loıc, 17, 161Chamoun, Sabine, 257Chang, Kuo-Chun, 23Chao, Xiaobo, 33Chapuis, Margot, 165Chardon, Valentin, 105Chassagne, Remi, 196Chatellier, Ludovic, 60Chauchat, Julien, 56, 129, 196Chavarrias, Victor, 216Chen, Shangzhi, 135Chen, Su-Chin, 76, 251Chen, Yuansheng, 284Cheng, Zhen, 56Chevalier, Christophe, 252Chibane, Tariq, 133Choi, Hehun, 293Chone, Guenole, 294Ciavola, Paolo, 34Cilli, Silvia, 34Claude, Nicolas, 40, 104, 240Clutier, Anne, 105, 262Compagnon, Franck, 165Conevski, Slaven, 149Constantinescu, George, 31Contreras, Marıa-Teresa, 32Cordero, Silvia, 69Cordier, Florian, 40, 104Cornett, Andrew, 283Coscarella, Francesco, 19Costabile, Pierfranco, 288Costanzo, Carmelina, 288Courret, Dominique, 60, 244Courtois, Estelle, 64Couto, Lucia, 117Creelle, Stephan, 115

Crosato, Alessandra, 81, 104, 190, 213

Czerny, Rebekka, 63

da Cunha, Evandro, 286

Das, Bhabani-Shankar, 86, 118

Dashtpeyma, Hamed, 141

Daubagnan, Lea, 221

David, Laurent, 60

de Cesare, Giovanni, 22, 257

de Jong, Jurjen, 139

de Linares, Matthieu, 145

de Mulder, Tom, 115, 269

de Ruijsscher, Timo, 68, 228

de Santis, Rosa, 288

Deleersnijder, Eric, 267

Delenne, Carole, 157

Delestre, Olivier, 36

Dellinger, Guilhem, 135

Delus, Claire, 279

Denda, Masatsoshi, 229

Desai, Venkappayya R, 93

Deshpande, Vishal, 151

Despax, Aurelien, 179

Detert, Martin, 63, 276

Devi, Kamalini, 86, 118, 204

Dewals, Benjamin, 134, 155, 211

Dey, Subhasish, 51, 78, 93

Dhont, Blaise, 80

di Cristo, Cristiana, 211

di Leonardo, Alice, 45

Diplas, Panayiotis, 287

Dittrich, Andreas, 103

Domhof, Boyan, 88

Dominguez, Lucas, 167

d’Oria, Marco, 25

Dorren, Luuk, 235

Downs, Peter, 79

Dramais, Guillaume, 37, 264

Driessen, Tjeerd, 109

Dubos, Virgile, 275

Duclercq, Marion, 240

Dudill, Ashley, 21

Duguay, Jason, 114

Dumoutier, Quentin, 232

Dupuis, Victor, 16

Durand, Edouard, 252

Duro, Gonzalo, 190

Dustegir, Md. Maruf, 210

Echeverribar, Isabel, 30

Eiff, Olivier, 15–17, 161, 170

El kadi Abderrezzak, Kamal, 119, 211, 240

298

Elyakime, Pierre, 16, 161

Engelen, Lukas, 115

Eom, Jung-Hyun, 132

Erpicum, Sebastien, 155

Escauriaza, Cristian, 32, 184

Evette, Andre, 174

Fairweather, Kirsti, 199

Fang, Chunming, 254

Fankhauser, Andres, 124

Farhadi, Alireza, 96

Fathel, Siobhan, 172

Feng, Jiawei, 257

Fent, Ilaria, 95

Fernandes, Joao, 83

Fernandez-Pato, Javier, 138

Ferrari, Alessia, 25

Ferreira da Silva, Ana Maria, 102

Ferreira, Fabiana, 286

Ferreira, Rui, 13, 85

Ficsor, Johanna, 263

Finaud-Guyot, Pascal, 135

Fiorot, Guilherme, 286

Florens, Emma, 252

Fontaine, Firmin, 143

Fox, Garey, 166

Fraga, Bruno, 278

Franca, Mario, 95, 146, 238

Francalanci, Simona, 43

Franzini, Fabian, 153

Fretaud, Thierry, 145

Frey, Philippe, 196

Friedrich, Heide, 77, 193, 194, 277

Froehlich, David, 147

Fromant, Guillaume, 129

Fuchs, Sven, 91

Fujita, Ichiro, 201, 202, 225

Fukuoka, Shoji, 188

Furbish, David, 172

Furlan, Paloma, 101

Furuta, Takanori, 225

Galia, Tomas, 73, 169

Garambois, Pierre, 135

Garcıa-Navarro, Pilar, 30, 53, 99, 138

Garcıa-Palacın, Jose-Ignacio, 99

Gasiorowski, Dariusz, 258

Gasser, Eric, 235

Gaudio, Roberto, 19, 93

Geay, Thomas, 127, 128

Geiger, Franz, 59

Gems, Bernhard, 91, 111

Gerstgraser, Christoph, 187Ghaffarian, Hossein, 97Ghenaim, Abdellah, 135Gilja, Gordon, 230Glas, Martin, 191Goncalves Junior, Vicente, 286Gourbesville, Philippe, 156Goutal, Nicole, 36, 272, 275Gratiot, Nicolas, 267Greco, Massimo, 211Grigoriadis, Dimokratis, 13Groom, Jane, 194Grossi, Giovanna, 265Grottoli, Edoardo, 34Grover, Patrick, 102Gu, Jung-Eun, 234Guan, Jianzhao, 254Guerrero, Massimo, 49, 82, 149Guertault, Lucie, 166Guillen-Ludena, Sebastian, 124Guinot, Vincent, 157Gutierrez, Ronald, 167Gymnopoulos, Miltiadis, 85

Habersack, Helmut, 96, 191Habit, Evelyn, 61Hager, Willi H., 52Hakiel, Jakub, 258Halfi, Eran, 151Han, Kun-Yeun, 293Han, Xun, 57Hanmaiahgari, Prashanth R., 207, 237Hara, Yuji, 256Hatz, Marcus, 107Hauet, Alexandre, 128, 221Haun, Stefan, 120, 122, 144Hayakawa, Hiroshi, 241Heckele, Christoph, 17Hela, Romdhane, 41Hengl, Michael, 192Henry, Pierre-Yves, 205, 266Hicks, D. Murray, 226Higashi, Yutaka, 176Hillebrand, Gudrun, 48Hinkelmann, Reinhard, 134, 156Hissler, Christophe, 279Hoffmann, Thomas, 48Hoitink, Ton, 67, 68, 224, 228Horna-Munoz, Daniel, 31Hostache, Renaud, 279Houssier, Jerome, 105Hradecky, Jan, 169

299

Hsu, Tian-Jian, 56Hu, Chunhong, 254Hua, Leina, 197Huang, Cheng-Chia, 23Huang, He-Qing, 236Huang, Pin-Chun, 291Hubl, Johannes, 235Hugerot, Therese, 143Hulscher, Suzanne, 88Hurther, David, 129

Iervolino, Michele, 211Iribarren, Pablo, 71Ishikawa, Tadaharu, 108Islam, Md Kabirul, 210Iwasaki, Toshiki, 152

Jafarnejad, Mona, 121Jang, Chang-Lae, 175Jarvela, Juha, 42Jesudhas, Vimaldoss, 142Ji, Un, 44, 175Jodeau, Magali, 145, 257, 272Johnson, Joel, 151Jones, Keaton, 198Jourdain, Camille, 40Juez, Carmelo, 146Jung, Sang Hwa, 175, 234

Kadota, Akihiro, 295Kainz, Silke, 192Kalinowska, Monika, 183Kampel, Irina, 111Kanda, Keiichi, 38Kang, Joongu, 175, 178, 234, 245Kang, Seokkoo, 58Kantoush, Sameh, 119, 246Katoshevski, David, 151Kawaike, Kenji, 231Kazay, Daniel, 223Kazuhiko, Matsunobu, 28Keller, Florian, 91Keshavarzi, Alireza, 182Khatua, Kishanjit K., 86, 87, 118, 204Khodashenas, Saeed-Reza, 261Khuntia, Jnana-Ranjan, 86, 204Kibriya, Numan Al, 210Kim, Changsung, 245Kim, Donggu, 44Kim, Dongsu, 179, 180Kim, Hyung-Jun, 273, 274Kim, Ji Hyun, 245Kim, Ji-Hyun, 44

Kim, Ji-Sung, 132Kim, Jongmin, 180Kim, Myounghwan, 132Kim, Sungjoong, 178Kim, Sungjung, 44Kimura, Ichiro, 98, 212, 271Kinzel, Paul, 176Kirkil, Gokhan, 163Kitano, Claudio, 286Kitao, Tomonori, 241Kitazono, Kazuya, 98Kjeldsen, Thomas, 131Kleinhans, Maarten, 35, 190Knox, Paul, 283Ko, Dongwoo, 44, 178Kobayashi, Kenichiro, 134, 156Kobayashi, Sohei, 246Koca, Kaan, 185Kojima, Takashi, 28Koll, Katinka, 90, 187, 250Koshiba, Takahiro, 126Kubın, Miroslav, 169Kuczera, George, 168Kuno, Yuka, 256Kuspilic, Neven, 230Kwoll, Eva, 199

Labeur, Robert-Jan, 216Laborde, Anita, 61Lacey, Jay, 114Lagouy, Mickael, 37, 264Lai, Jihn-Sung, 23Lam, Norris, 200Lang, Michel, 226Laronne, Jonathan, 151Larrarte, Frederique, 252Le Bescond, Chloe, 37, 264Le Coz, Jerome, 37, 50, 179, 226, 264, 281Le, Hoang-Anh, 267Le, Minh-Hoang, 275Leal, Joao, 83Lee, Chanjoo, 44Lee, Du-Han, 132, 180Lee, Fong-Zuo, 23Lee, Kwan-Tun, 291Lee, Namjoo, 245Lefevre, Arnaud, 208Legleiter, Carl, 176Legout, Cedric, 47Lemkecher, Fatma, 60Leopardi, Angelo, 211Lepesqueur, Jeremy, 279

300

Leroux, Clement, 240Li, Danxun, 276Li, Xiaobin, 284Li, Zhiwei, 236Liang, Dongfang, 134, 156Liang, Min-Chih, 76Liebault, Frederic, 125, 143Liedermann, Marcel, 191Lima, Maria Manuela, 248Lin, Pengzhi, 57Lin, Yung-Bin, 23Lindermuth, Adrian, 111Link, Oscar, 20, 61Linkens, Jeremy, 153Liu, Xiaofeng, 56Liu, Xiaoqin, 23Loccufier, Mia, 269Lockwood, Kenneth, 102Loire, Remi, 232Lopez, Diego, 97Lorke, Andreas, 185Loson, Benoit, 279Løvoll, Aslak, 66Lyon, Steve, 200

Ma, Xiaoyi, 284Macchione, Francesco, 288Maciel, Geraldo, 286MacVicar, Bruce, 114, 141Magnuszewski, Artur, 183Mahananda, Minakshee, 207Maıtre, Anthony, 238Maji, Soumen, 237Maldonado, Luiz, 223Manceau, Luc, 279Manes, Costantino, 19Mansanarez, Valentin, 200, 226Manso, Pedro A., 124Mao, Luca, 71, 148, 184Marchal, Moıse, 16Marsooli, Reza, 33Martınez-Aranda, Sergio, 53Martel, Nancy, 186Martinez-Carreras, Nuria, 279Mathieu, Antoine, 56Mathilde, Cuchet, 59Matos, Jorge, 101Matousek, Vaclav, 214Maurin, Raphael, 196Mayen, Vincent, 165Mazzorana, Bruno, 71, 91McAlpin, Tate, 198

McDonald, Richard, 176

McLean, Dave, 21

McLelland, Stuart, 17

Meiburg, Eckart, 197

Memar, Sargol, 22

Michioku, Kohji, 38

Mieras, Ryan, 129

Mignosa, Paolo, 25

Mignot, Emmanuel, 97, 116, 184, 208, 281

Mikami, Tetsuaki, 28

Millares, Agustın, 46, 260

Misset, Clement, 47, 128

Mitrou, Elli, 278

Monino, Antonio, 46

Montabonnet, Lucas, 174

Montarges-Pelletier, Emmanuelle, 279

Morales-Hernandez, Mario, 30, 138

Morikawa, Go, 271

Morita, Saichiro, 249

Morlot, Thomas, 221

Mosseri, Julie, 232

Moulin, Frederic, 15–17, 161

Mouris, Kilian, 122

Muhawenimana, Valentine, 62

Mulahasan, Saad, 285

Muller-Hagmann, Michelle, 206

Murillo, Javier, 53, 140

Murphy, Brendan, 17

Murzyn, Frederic, 142

Muste, Marian, 179

Nagel, Tim, 56

Nakagawa, Hajime, 231

Naqshband, Suleyman, 68, 228

Nardone, Paride, 90, 187

Navaratnam, Christy U., 205, 266

Navas-Montilla, Adrian, 140

Nelson, Jonathan, 176

Niewerth, Stephan, 268

Nikora, Nina, 12

Nikora, Vladimir, 12, 160, 164

Noack, Markus, 144

Nones, Michael, 187

Norris, Stuart, 277

Noss, Christian, 185

Notoya, Yuichi, 202, 225

Nunez-Gonzalez, Francisco, 103, 250

Oishi, Satoru, 134, 156

Olsen, Nils-Reidar, 120

Osawa, Yuki, 38

Oss Cazzador, Daniele, 148

301

Ota, Kazuyuki, 54

Oukacine, Marina, 275

Ousset, Frederic, 174

Ozeren, Yavuz, 209

Ozgen, Ilhan, 134, 156

Padhi, ellora, 93

Pagliara, Stefano, 24

Palermo, Michele, 24

Papanicolaou, Thanos, 215

Papathoma-Kohle, Maria, 91

Paquier, Andre, 133

Park, Inhwan, 273, 274

Park, Jun-Hyung, 293

Parker, Gary, 57

Parsapour-Moghaddam, Parna, 106

Pego, Joao Pedro, 117

Pelmard, Joe, 277

Penna, Nadia, 93

Penning, Ellis, 2, 175

Peretz, Yael, 151

Perkins, Richard, 116

Perona, Paolo, 235

Perret, Emeline, 171

Perrot-Minot, Clement, 116

Perry, Brian, 283

Persi, Elisabetta, 99

Pessenlehner, Sebastian, 191

Petaccia, Gabriella, 99

Peteuil, Christophe, 145

Petrut, Teodor, 127

Pfister, Michael, 101

Pham Van Bang, Damien, 104

Piegay, Herve, 8, 97, 105, 232

Picco, Lorenzo, 148

Pinkse, Arthur, 213

Pirotton, Michel, 155

Piton, Guillaume, 143, 174

Plumb, Benjamin, 265

Poggi, Davide, 69

Poirel, Alain, 47

Ponte, Yoch, 167

Pophet, Nuttita, 33

Posi, Sara, 174

Pouchoulin, Sebastien, 281

Pradhan, Arpan, 87

Pretet, Thomas, 262

Prinos, Panayotis, 85

Proust, Sebastien, 118, 164, 204

Puleo, Jack, 129

Qin, Jie, 205

Quillien, Bernard, 208

Rachelly, Cristina, 243

Radice, Alessio, 172, 173

Rainato, Riccardo, 148

Ravanat, Xavier, 174

Ravazzolo, Diego, 71

Recking, Alain, 47, 127, 128, 143, 174, 195

Reid, Ian, 151

Renard, Benjamin, 226

Rennie, Colin, 106, 149, 199, 283

Revil-Baudard, Thibaut, 129

Rhee, Dong-Sop, 273, 274

Ribolzi, Olivier, 267

Ricardo, Ana M., 13

Richard, Sylvain, 244

Rickenmann, Dieter, 150

Ridolfi, Luca, 239

Rifai, Ismail, 211

Riviere, Nicolas, 97, 116, 208, 281

Robinson, Christopher, 238

Rodrigues, Stephane, 104

Rodriguez, Jose, 168

Rogers, Ashley, 19

Rollin, Xavier, 64

Romero, Elio, 223

Romero, Romu, 289

Roth, Anita, 121

Roussinova, Vesselina, 162

Roux, Helene, 244, 289

Rouzes, Maxime, 15

Rowinski, Pawe l, 183

Ruiz-Villanueva, Virginia, 71

Ruman, Stanislav, 169

Ruther, Nils, 49, 82, 149, 266

Rutschmann, Peter, 59

Ryu, Yonguk, 175, 178

Saber, Mohamed, 119

Saco, Patricia, 168

Saintilan, Neil, 168

Sandi, Steven, 168

Sandoval, Jorge, 184

Santini, William, 267

Sanz-Ramos, Marcos, 289

Sao, Yuri, 286

Sassa, Naohiko, 256

Sato, Nobuo, 241

Sato, Takahiro, 54

Savary, Celine, 70

Schalko, Isabella, 100

Schielen, Ralph, 109

302

Schindfessel, Laurent, 115, 269Schippa, Leonardo, 34Schleiss, Anton J., 5, 22, 101, 121, 124, 146,

238, 257Schmidt, Franziska, 252Schmitt, Laurent, 105Schmocker, Lukas, 100Scholten, Martin, 139Schuh, Carina, 107Schutz, Cornelia, 63Schwarz, Massimiliano, 235Schwegler, Benno, 124Schwindt, Sebastian, 121Secher, Matthieu, 145, 262, 272Seleem, Omar, 295Senoo, Hiroshi, 108Seo, Il Won, 176Seong, Hoje, 273, 274Serouilou, Jordane, 105Sevrez, Damien, 110Shimizu, Yasuyuki, 212Sibilla, Stefano, 99Sieben, Arjan, 67Simon, Andrew, 235Sindelar, Christine, 96Skarpich, Vaclav, 73, 169Slaney, Jonathan, 106Sloff, Kees, 67Smart, Graeme, 27, 226Snaps, Jean-Charles, 153Soar, Philip, 79Soares-Frazao, Sandra, 95, 153, 157, 267Solari, Luca, 43, 174, 195Son, Geunsoo, 180Søras, Sigurd, 49Souriguere, Katia, 165Spitzer, Detlef, 250Spreitzer, Gabriel, 77Spruyt, Aukje, 88, 139Stagonas, Dimitris, 131Stahly, Severin, 238Stamataki, Ioanna, 131Stamm, Jan, 124Stecca, Guglielmo, 216Steeb, Nicolas, 150Stephan, Ursula, 192Stewart, Mark, 160Stoesser, Thorsten, 278Stoffel, Markus, 71Stokseth, Siri, 49, 82Sturm, Michael, 91Sumi, Tetsuya, 119, 126, 246, 249

Suto, Hitoshi, 54Suzuki, Takamasa, 119Suzuki, Waku, 246Suzuta, Hiromi, 28Swartenbroekx, Catherine, 70Szydlowski, Michal, 258Szymkiewicz, Romuald, 258

Taccone, Florent, 36Tailliez, Cyrille, 279Takahisa, Gotoh, 188Takemon, Yasuhiro, 119, 246Talchabhadel, Rocky, 231Tamas, Eniko Anna, 263Tanda, Maria Giovanna, 25Tanganelli, Francesco, 195Tani, Kojiro, 201, 202Tassi, Pablo, 40, 104, 240Terfous, Abdelali, 135Termini, Donatella, 45Terrell-Ramos, Travis, 176Terrier, Benoıt, 165Terwisscha van Scheltinga, Renske, 193Tewolde, Meles S., 247Tfwala, Samkele, 76, 251Thalmann, Matthias, 146Thollet, Fabien, 37, 264Tichavsky, Radek, 73Tiga, Tsegaye, 213Tominaga, Akihiro, 256Tomizawa, Shinjiro, 28Toniati, Andre, 286Trevisson, Michele, 17, 170Tritthart, Michael, 96, 191Truong-Hong, Son, 14Tsuji, Issei, 202Tunnicliffe, Jon, 77

Uchida, Tatsuhiko, 282Uijttewaal, Wim, 14, 81, 190Ung, Philippe, 272Unigarro, Stefania, 173

Vacca, Andrea, 211Vacondio, Renato, 25Valette, Eric, 145, 272van Audenhaege, Loic, 64van der Wal, Maarten, 67van Dijk, Wout, 35Vargas-Luna, Andres, 81Vasquez, Jose, 21Vasquez-Tarrio, Daniel, 125Vastila, Kaisa, 42

303

Venas, Bard, 66Venditti, Jeremy, 199Vergne, Adrien, 50Vermeulen, Bart, 67Vesipa, Riccardo, 239Vetsch, David F., 243Viero, Daniele P., 154Viparelli, Enrica, 247Viseu, Teresa, 117Voortman, Bert, 109Vowinckel, Bernhard, 197

Walder, Stefan, 111Waldhoer, Christoph, 111Wang, Dayu, 254Warmink, Jord, 88Watanabe, Akihide, 28Wei, Yao, 284Weitbrecht, Volker, 100, 243, 276Wen, Li, 168Westerberg, Ida, 200Williams, Priscillia, 162Wilson, Catherine, 62Winterscheid, Axel, 149

Wirz, Carole, 145Wohl, Ellen, 71Woo, Hyoseop, 234Wren, Daniel, 209Wullems, Bas, 228Wunder, Sina, 17Wyssmann, Micah, 215

Yabe, Hiroki, 152Yamaguchi, Satomi, 152Yao, Wei-Wei, 236Yeo, Hongkoo, 245Yossef, Mohamed, 139Yu, Guo-An, 236

Zaid, Bahaeldeen, 187Zampiron, Andrea, 160Zang, Jun, 131Zanker, Sebastien, 127, 128Zhang, Lei, 254Zhao, Jiaheng, 134, 156Zima, Piotr, 258Zounemat-Kermani, Mohammad, 22Zrostlik, Stepan, 214

304

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