wallingford - may 2002 dam-break floods and sediemnt movement 1 impact - wp4 dam-break induced...

Wallingford - May 2002

Dam-break floods and sediemnt movement

1

IMPACT - WP4IMPACT - WP4

Dam-break inducedDam-break induced floodsfloodsand sediment movementand sediment movement

State of the art and need for research

Université catholique de Louvain

Yves Zech and Benoit Spinewine



2

Aims and objectivesAims and objectives

Improve the prediction

of the motion of sediments

in association with catastrophic floods



3

Solid transport and extreme flowsSolid transport and extreme flows



4

Types of catastrophesTypes of catastrophes

• Dam break• Debris flows, mud flows and lahars• Floating debris and clogging• Glacial lake outburst flood (GLOF)• Landslides

– Bank failure into the dam reservoir– Obstruction by natural dams



5

Former EU researchesFormer EU researches

• Natural hazardsMITCH

• Mitigation of climate induced natural hazards

• January 2001 - 24 months - 13 partners (HR Wall)



6


• Torrents and sedimentsTHARMIT

• Torrent hazard control in the European Alps. Practical tools and methodologies for hazard assessment and risk mitigation

• July 2000 - 30 months - 11 partners (UDT, Cem)

EROSLOPE II• Dynamics of sediments and water in alpine

catchments - processes and prediction• June 1996 - 36 months - 10 partners (Cem,

UDT)



7


• DebrisDAMOCLES

• Debrisfall assessment in mountain catchment for local end-users

• March 2000 - 36 months - 6 partners

DEBRIS-FLOW-RISK• Debris flow management and risk

assessment in the Alpine region• October 1996 - 30 months - 9 partners

(Cem, UDT)



8


• Glaciological hazardsGLACIORISK

• Survey and prevention of extreme glaciological hazards in European mountainous regions

• January 2001 - 36 months - 11 partners (Cem)



9


• Avalanches and landslidesCADZIE

• Catastrophic avalanches: defence structures and zoning in Europe

• April 2000 - 30 months - 10 partners (Cem)

ALERT• Avalanche and landslip early reporting

technology • December 1997 - 4 months - 2 partners



10


• Avalanches and landslides (2)Landslide hazards

• New technologies for landslide hazard assessment and management in Europe

• July 1996 - 24 months - 11 partners

Large-volume landslides• Major risk from rapid, large-volume

landslides in Europe: the design and testing of new techniques for hazard assessment and mitigation

• January 1998 - 24 months - 7 partners



11


• Avalanches and landslides (3)Landslide and avalanche risks

• Concerted action on forecasting prevention and reduction of landslide and avalanche risks

• January 1998 - 30 months - 5 partners

Mechanisms of landslides• Mechanisms of catastrophic landslides • January 1998 - 24 months - 6 partners



12

Issues of IMPACT WP4 Issues of IMPACT WP4 researchresearch

• Extreme flows

intense erosion and solid transport

• Intense sediment transport

affects flood-wave prediction– Arrival time– Maximum water level– Morphological changes



13

Scope of the researchScope of the research

• Near-field – Severe transient debris flow

• Far-field – Intense transport– Bank erosion and geomorphic changes



14

Near field : problems to be solvedNear field : problems to be solved

• Initiation of movement– Vertical effects– Inertial effects– Sediments bulking

• Propagation– Intense scouring– Debris-flow front



15

Far field : problems to be solvedFar field : problems to be solved

• Transition from near-field to far-field• Geomorphic changes

– Bank erosion and failure• Tractive forces applied• Failure mechanism

– Channel widening– Deposition of material

• De-bulking• Distribution of sediments• Formation of secondary dams



16

Overall approachOverall approach

Combine

physical experiments

with the development and testing of

mathematical modelling methods

to improve our understandingof these flows



17

State of the artState of the art

• Near field– Experimental approach– Physical approach– Numerical approach

• Far field– Experimental approach– Physical approach



18

Near field : experimental Near field : experimental approachapproach

• Regime– Uniform flow, e.g. debris flow (UDT)– Severe transients, e.g. dam break

(UCL, UDT, IST, NTU)

National Taiwan University



19


• Solid transport mode– Intense bed load– Debris-flow rheology (UDT)

• Boundary conditions (water & sediment)

UCL



20


• Material– Light pearls (Taiwan)– PVC pellets (Trento, UCL)– Sand (Beira interior, IST, UCL)




21


• Grain-size distribution– Uniform– Graded

Universityof Trento



22


• Floating debris (Mississippi, Alberta)



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• Measurement techniques– Gauges– Interfaces imaging– Particle tracking

• Tracking of tracers particles• Bed material tracking



24

Near field : physical approachNear field : physical approach

• Sediment inertia– Acting forces

• Near-field erosion– Mobilisation of granular bed– Scour hole

• Formation of a debris-flow– Hydraulic jump– Mixture of sediments and water



25

Near field : numerical approachNear field : numerical approach

• Flow description– Analytical (UDT, UCL)– Shallow-water description

• 1D• 2D-H

– 2D-V• Hydrodynamics (ETHZ, Tianjin)• Tentative modelling with sediments (NTU,

UCL)

UCL



26

Near field : numerical approachNear field : numerical approach

• Transport modelling– Uncoupled hydrodynamics & solid

transport– Coupled description

• Sediment inertia• Momentum exchanges

– Multiphase description



27

Near field : former studiesNear field : former studies

University of Trento

• Uniform debris-flow experiments



28


• Mature debris flow



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• Mature debris flow



30


Z(cm)

V (m/s)

v w u

- 0.2 0 0.2 0.4 0.61

2

3

4

5

6

7

Velocity



31


c

zcm

Concentration



32


• Dam-break experiments

University of Louvain



33


• Mathematical description– Shallow water– Velocity and concentration



34


• Numerical results in simplified cases– Finite volumes– Fluxes according to Roe– Non equilibrium

UCL



35


• Limitations of existing models

0h

gt

0h

x



36

Near field : research programmeNear field : research programme

• Laboratory work– Acting forces, flow resistance– Dam-break flows : near-field features



37


• Acting forces, flow resistance (UDT)– Uniform material

• Months 1-18

– Graded material• Months 18-32

Benchmark



38


• Dam-break flows : near field (UCL)– Uniform material

• Months 1-9

Benchmark

Various water levelsVarious sediment levels



39


• Mathematical modelling (UCL)– 1D model: months 1-10

• Velocity distribution• (Concentration distribution)



40


• Mathematical modelling (UCL)– 2D-V model: months 21-32



41


• Validation of codes (UDT, UCL, Cem)– Debris flow

• Months 11-12

– Dam-break flow in the near field• Months 11-12



42

Far field : experimental Far field : experimental approachapproach

• Numerous data from real cases– Lawn Lake dam failure (Colorado,

1982)– Lake Ha!Ha! dike failure (Quebec,

1996)



43

Far field : experimental Far field : experimental approachapproach

• Bank failure experiments– River meandering– River braiding

• Breachingprocesses

UCL



44

Far field : physical approachFar field : physical approach

• Transition from near- to far-field– Sediment de-bulking– Front-plug piping and overtopping




45

Far field : physical approachFar field : physical approach

• Valley widening– Bank scouring– Bank collapse

• Sediment re-distribution– Bed deposition



46

Far field : numerical approachFar field : numerical approach

• Extension of shallow-water equation– Two-phase flow description

• River width adjustment• 3D de-coupled modelling

– Bends

Does not match the dam-break problem



47

Far field : former studiesFar field : former studies

• Bank erosion experiments

University of Louvain



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• Bank erosion experiments



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Submerged sand

Dry sand

Humid sand

37°

37°

85°

• Principle experiments



50




51


• Bank failure mechanism

50°

37°

85°

Vbank



52


6 cm

19 cm

50°

UCL



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UCL



54


• Numerical result (without water)



55


• Limitation of numerical description– Need for 2D approach– Need for coupling

• Limitation of physical description– Bank-failure mechanism : 3D features– Rheological aspects of bank failure– Suspended load and re-suspension



56

Far field : research programmeFar field : research programme

• Laboratory work– Dam-break in an initially prismatic valley

(UCL)• Months 13-20

– Similar tests in large-scale model (Châtelet)

– Large-scale enlargement (Châtelet)• Months 24-31



57


• Numerical modelling– Extension of 2D-H model (UCL)

• Bank erosion• Months 12-20



58


• Validation (UCL, UDT, Cemagref, IST)– Benchmarks

• Laboratory tests• WP2 Norwegian dam• Lake Ha!Ha!



59

IMPACT - WP4IMPACT - WP4

Dam-break inducedDam-break induced floodsfloodsand sediment movementand sediment movement

State of the art and need for research

Université catholique de Louvain

Yves Zech and Benoit Spinewine

wallingford - may 2002 dam-break floods and sediemnt movement 1 impact - wp4 dam-break induced...

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