sediment problems and sediment management in …hydrologie.org/redbooks/a349/p349 description,...

Sediment Problems and Sediment Management in

Asian River BasinsEdited by Des E. Walling IAHS Publ. 349 (2011) ISBN 978-1-907161-24-7, 224 + viii pp. Price £52.00

Sediment problems are assuming increasing importance in many Asian river basins and can represent a key impediment to sustainable development. Such problems include accelerated soil erosion, reservoir sedimentation and the wider impact of sediment on aquatic ecology, river morphology and water resource exploitation. They are further complicated by the impact of climate change and other components of global change in causing both increases and decreases in the sediment load of many rivers in recent years. In order to address these problems, sediment management must be seen as a central component of integrated river basin management. This volume, arising from a workshop organised jointly by the International Commission on Continental Erosion (ICCE) of IAHS, the UNESCO International Sediment Initiative (ISI) and the World Association for Sedimentation and Erosion Research (WASER), focuses on sediment problems in Asian river basins and the many difficulties involved in their effective management. The first section comprises overviews of the sediment problems experienced by individual countries or particular issues relating to the wider region; and the second documents case studies that deal with specific problems and their management. The overviews highlight the sediment problems faced by India and Iran, including soil erosion and reservoir sedimentation; recent changes in the sediment loads of the Hindu Kush-Himalayan rivers and their wider implications; the impact of human activity on the sediment loads of Asian rivers; and new challenges for erosion and sedimentation research in China linked to contemporary issues.

Preface

This Publication is based on the contributions presented at a 2-day workshop on Sediment Problems and Sediment Management in Asian River Basins, which formed part of the Scientific Assembly of the International Association of Hydrological Sciences (IAHS) and the International Association of Hydrogeologists (IAH), held in Hyderabad, India from 7 to 11 September 2009. The workshop was a collaborative venture between the International Commission on Continental Erosion (ICCE) of IAHS, the UNESCO International Sediment Initiative (ISI) and the World Association for Sedimentation and Erosion Research (WASER). The involvement of the UNESCO ISI was particularly important, because UNESCO provided funds to support the attendance of several invited speakers. Additionally the UNESCO ISI has provided funds to support the publication of this Proceedings Volume.

The workshop represented an explicit attempt to strengthen the interaction of ICCE, ISI and WASER with sediment specialists in Asia, and particularly in India and the surrounding countries, and to focus attention on the many important sediment problems faced by the region. The programme of the workshop included the presentations made by the invited speakers and by others who had offered papers to the workshop. The submitted papers provided coverage of a wide range of specific issues and problems. In compiling this collection of papers, the contributions presented at the Workshop have been supplemented by a number of additional contributions by authors who had expressed interest in the Workshop but who were unfortunately unable to attend. These additional papers provide a valuable complement to those presented at the Workshop and usefully expand the coverage of this volume.

The papers included in this publication have been subdivided into two groups. The first group comprises overview papers, which describe the sediment problems experienced by particular countries or focus on particular issues relating to the wider region. The second group comprises papers documenting case studies that deal with particular problems and their management. The overview papers include contributions highlighting the various sediment problems faced by India and Iran, including soil erosion and reservoir sedimentation; recent changes in the sediment loads of the Hindu Kush-Himalayan rivers and their wider implications; the impact of human activity on the sediment loads of Asian rivers; and new challenges for research on erosion and sedimentation in China linked to key contemporary issues.

The case studies provide valuable examples of a range of current sediment problems in Asian river basins and the development of management strategies to address these problems. Two contributions focus on soil erosion. One describes the problems of channel aggradation and reduction in drainage density encountered in many small rivers in Siberia as a result of land clearance and intensification of agricultural activity, and the other addresses the important issue of establishing the magnitude of ‘natural’ or background erosion rates, using an area of the hilly Sichuan Basin in China as an

example. Such information is frequently an important requirement when defining management objectives. Problems of developing sediment measurement programmes that are capable of providing reliable information on the response of sediment loads to changing catchment conditions are addressed by two papers. One deals with a small catchment in northern Thailand subject to land-use change and the other describes the establishment of a new monitoring programme for the Upper Ramu River on New Guinea Island, aimed at documenting changes in sediment and related contaminant fluxes associated with the expansion of mining activity within the river basin. The value of using the sediment budget as a tool for characterizing the sediment response of a river basin is usefully demonstrated by a study undertaken in the 3800 km2 Lake Inle catchment in Myanmar and this contribution further demonstrates the wider socio-economic implications of the sediment budget. Taiwan is well known for its high sediment yields and another paper emphasises the sensitivity of this environment to recent climatic change, and particularly the increasing incidence of typhoons. Prediction and modelling of sediment yields are frequently important requirements for developing improved sediment management strategies, because of the need to identify key source areas within a river basin, and two papers report the development and application of such models in the Upper Citarum basin in Indonesia, where landslides are an important driver of sediment mobilisation, and in the catchment of the Sriramsagar Reservoir in India. The impact of human activity on rivers and their sediment loads provided a key theme of the Workshop and case studies of the impact of sand mining in Sri Lanka and the problems of channel degradation along the Yangtze River in China, resulting from the reduction in the sediment load of this river caused by the construction of the Three Gorges Dam, provide additional evidence of the importance of such impacts. .

Reservoir sedimentation represents an important problem in many areas of Asia and four papers provide valuable perspectives on different aspects of this problem. One paper focuses on the potential for using satellite remote sensing imagery to support reservoir sedimentation surveys in India, and another reports on sedimentation in the Akdarya Reservoir in Uzbekistan and its implications for water resource management. The problems of managing reservoir sedimentation in a reservoir constructed on a large river with a high sediment load are well illustrated by a paper describing the development of a sediment management strategy for the Xiaolangdi Reservoir on the Lower Yellow River in China, and the local problems associated with the development of oblique flows in close proximity to many barrrages on Indian rivers are described by a further case study. The deltas and estuaries located at the outlets of river basins frequently face many problems associated with sediment management and their significance is emphasised by a final case study that describes the problems of managing the densely populated Meghna Estuary in Bangladesh, which channels water from the Ganges, the Brahmaputra and the Meghna River into the Bay of Bengal and which is highly sensitive to floodwater and sediment inputs from the contributing river basins as well as potential changes in sea level.

Thanks are extended to all those who helped in the organisation of the workshop, including Manfred Spreafico, Jim Bogen, Chunhong Hu and Anil Mishra, who were co-convenors with myself, and Bhanu Neupane, Ramasamy Jayakumar and Anil Mishra from UNESCO, who worked behind the scenes to secure financial support for several

participants and to make their travel and accommodation arrangements. Anil Mishra, from the UNESCO Division of Water Sciences in Paris, is also thanked for his encouragement and support throughout the production of this publication. Finally, very special thanks are due to Penny Perrins and Cate Gardner at IAHS Press in Wallingford for coordinating the production and publication of this volume.

Des E. WallingGeography, College of Life and Environmental Sciences, University of Exeter

Amory Building, Rennes Drive, Exeter, EX4 4RJ, UK

Contents

Preface by Des E. Walling v

1 Overview Papers

Sediment problems and sediment management in the Indian Sub-Himalayan region Umesh C. Kothyari

3

An overview of sediment problems and management in Iran Seyed Hamidreza Sadeghi

14

The changing sediment loads of the Hindu Kush-Himalayan rivers: an overview X. X. Lu, S. R. Zhang, J. C. Xu & J. Merz

21

Human impact on the sediment loads of Asian rivers Des E Walling 37

New challenges in erosion and sedimentation research: a Chinese perspective Zhaoyin Wang, Lijian Qi, Guoan Yu & Cheng Liu

52

2 Case Studies

Agricultural activity as cause of aggradation of small Siberian rivers Valentin Golosov, Nadezda Ivanova & Svetlana Ruleva

73

Natural erosion rates and sediment delivery ratios in the Hilly Sichuan Basin, southwest China, since the Mid-Pleistocene Hongwei Zhu, Xinbao Zhang, Anbang Wen, Yunqi Zhang, Yangchun Wang, Yongqing Qi & Xiubin He

80

Sediment load monitoring in the Mae Sa catchment in northern Thailand Alan D. Ziegler, Lu Xi Xi & Chatchai Tantasarin

86

River sediment monitoring for baseline and change characterisation: a new management tool for the Ramu River Communities in Papua New Guinea Nick A. Chappell, Wlodek Tych, Phil Shearman, Barbara Lokes & John Chitoa

92

Placing sediment budgets in the socio-economic context for management of sedimentation in Lake Inle, Myanmar Takahisa Furuichi & Robert J. Wasson

103

The changing rainfall–runoff dynamics and sediment response of small mountainous rivers in Taiwan under a warming climate Shuh-Ji Kao, J. C. Huang, T. Y. Lee, C. C. Liu & D. E. Walling

114

Spatially-distributed assessment of sediment yield and shallow landslide potential area in the upper Citarum River basin, Indonesia Apip, Kaoru Takara & Yosuke Yamashiki

130

Sediment yield investigations for controlling sedimentation in the catchment of the Sriramsagar reservoir, India B. Venkateswara Rao, K. Srinivasa Reddy & P. Ravi Babu

141

River sand mining and associated environmental problems in Sri Lanka Ranjana U. K. Piyadasa

148

Channel degradation in the Yangtze River after the impoundment of the Three Gorges Project Y. T. Li & J. Y. Deng

154

Assessment of reservoir sedimentation using remote sensing Sharad K. Jain & Sanjay K. Jain

163

Sedimentation of reservoirs in Uzbekistan: a case study of the Akdarya reservoir, Zerafshan River Basin Shavkat Rakhmatullaev, Frédéric Huneau, Masharif Bakiev, Mikael Motelica-Heino & Philippe Le Coustumer

171

Research on key technology for sediment management in large-scale reservoirs Dongpo Sun, Mingquan Geng & Cheng Liu

182

Sedimentation behind barrages and oblique river flow Kapileswar Mishra & Dhrubajyoti Sen

193

Sediment dispersal processes and management in coping with climate change in the Meghna Estuary, Bangladesh Maminul Haque Sarker, Jakia Akter, Md Ruknul Ferdous & Fahmida Noor

203

Key word index 219

Author index 221

_________________________________________________________________Sediment Problems and Sediment Management in Asian River Basins (Proceedings of the Workshop held at Hyderabad, India, September 2009). IAHS Publ. 349, 2011, 3-13.

Sediment problems and sediment management in the Indian Sub-Himalayan region

UMESH C. KOTHYARIDept. of Civil Engineering, Indian Institute of Technology, Roorkee-247667, India [email protected]

Abstract Alluvial rivers as well as gravel- and boulder-bed rivers in the Indian Sub-Himalayan region pose many problems for the inhabitants of the region. Landslides and floods triggered by heavy rainfall result in colossal damage to life and property. The design, construction and maintenance of dams, reservoirs, bridges and other infrastructure pose important challenges due to the complex role played by the sediment transported by the rivers of the region. This contribution reviews the current status of sediment management in the region by means of illustrative examples and sample data.Key words sediment; sediment problems; sediment management; Indian sub-Himalayan region

________________________________________________________________Sediment Problems and Sediment Management in Asian River Basins (Proceedings of the Workshop held at Hyderabad, India, September 2009). IAHS Publ. 349, 2011, 14-20.

An overview of sediment problems and management in Iran

SEYED HAMIDREZA SADEGHIDepartment of Watershed Management Engineering, College of Natural Resources and Marine Sciences, Tarbiat Modares University, Noor 46417-76489, Mazandaran, [email protected]

Abstract As a developing country, Iran currently faces many sediment-related problems. The high potential sensitivity of much of the country to erosion, inappropriate and unnecessary infrastructure development, land-use change, and unlawful exploitation of resources all contribute to increased soil erosion and sediment mobilisation and associated increased sediment fluxes. However, lack of recognition of the long-term value of soil, the limited numbers of hydrometric stations, the short duration of most records, unreliable and inconsistent data and information, lack of understanding of sediment yield processes and the apathy of both the population in general and experts in the field, serve to mask the severity and intensity of the problem. This contribution attempts to identify and describe the existing sediment problems in the country and presents a number of examples of major changes in sediment fluxes due to natural and human-induced controls. In the present paper an attempt is firstly made to identify and describe the existing problems in the country. Appropriate solutions aimed at combating or minimising the problems and developing effective sediment management strategies are proposed.Keywords soil erosion; land degradation; sediment management; sediment problems; Iran


The changing sediment loads of the Hindu Kush-Himalayan rivers: an overview

X. X. LU1, S. R. ZHANG2, J. C. XU3 & J. MERZ4

1 Department of Geography, National University of Singapore, 119260 Singapore

mailto:[email protected]

[email protected] College of Water Sciences, Beijing Normal University, Beijing 100875, China3 Kunming Institute of Botany and World Agroforestry Centre, Beijing, China4 Rural Development and Qualification, Water Conservancy Bureau, Tibet, China

Abstract The rivers originating from the Hindu Kush-Himalayas (HKH) are an important water resource for billions of people in Asia. These rivers used to contribute a large proportion of the global land–ocean suspended sediment flux and the Huanghe and the Ganges/Brahmaputra were characterized by the highest sediment loads of all world rivers. This paper identifies the key sediment source areas and identifies the main causes behind the recent dramatic changes in sediment load. The large river basins of this region can be broadly divided into several critical zones based on their elevations. The high plateau, with an elevation of >3500 m, has or will be affected by melting glaciers and snow as a result of global warming, and this in turn could generate increased sediment loads. The high mountainous areas with elevations ranging from 1000 to 3500 m on the northern side of the HKH and >1000 m on the southern side are the main sediment source areas, due to frequent slope failures and severe surface erosion. The main sediment source areas for some of the large rivers also include areas of lower elevation (around 500 m above sea level) with intensive human activity. Such areas include, for example, the Loess Plateau for the Huanghe, the hilly areas of the Sichuan Basin for the Changjiang, and the dry area in Bagan for the Irrawaddy. Most of these large river systems have been subject to a dramatic decline in sediment loads in recent years, due to both climate change and human impacts. The total sediment load transported from the HKH and neighbouring regions to the oceans has decreased by about half, from about 4.3 Gt year-1 prior to the 1980s, to ~2.1 Gt year-1

currently. The ranking of the large Asian rivers in terms of the annual sediment fluxes to the oceans has changed from the Brahmaputra, Huanghe, Ganges, Changjiang, and Irrawaddy in the pre-1980s to the Brahmaputra, Irrawaddy, Ganges, Changjiang, and Mekong in the post-1990s. The major Chinese rivers have become less important than those in the South, especially the Southeast Asian rivers, in terms of land–ocean sediment flux. It is anticipated that the sediment loads of the HKH rivers will continue to change due to intensive economic activity and the rapid pace of climate change in the region and throughout all the main river basins. It is possible that it will take a long time for the rivers to achieve equilibrium or quasi equilibrium. These dramatic changes can also give rise to important problems, including river channel/bank instability, loss of habitats, coastal instability, and sea water intrusion. Key words sediment load; water discharge; human impact; climate change; large Asian rivers; Hindu-Kush Himalayas (HKH); Tibet plateau


Human impact on the sediment loads of Asian rivers

DES E. WALLING Geography, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK [email protected]

Abstract The suspended sediment load of a river exerts a key influence on its aquatic ecology, its morphology and the exploitation of its water resources. Changes in the sediment loads of rivers can therefore have wide-ranging environmental and social and economic consequences. There is growing evidence that the sediment loads of many Asian rivers have changed significantly in recent years. Some have increased, whereas others have decreased. It is important that such changes should be seen in a longer term context. Although climate change is increasingly seen as a cause of changing sediment loads, human impact is generally recognised to be the key cause. The key drivers of these changes can be grouped into those causing increases and those causing decreases. The former include land clearance, land-use activities and other forms of catchment disturbance. The latter include sediment trapping by dams, soil conservation and sediment control programmes, and sand extraction from river channels. The changes shown by the sediment load of a river will reflect the spatial and temporal integration of the impacts of these drivers. The temporal pattern of change can reflect the contrasting temporal trajectories of the different drivers and a simple schematic model is presented whereby the records of sediment load for many Asian rivers are initially characterized by increases in response to land clearance and catchment disturbance, but subsequently decline in response to dam construction for both improved water supply and hydropower generation, the introduction of soil conservation and sediment control programmes to address problems of


sustainable development, and the extraction of sand from river channels to support the building construction associated with economic development. Key words suspended sediment loads; Asian rivers; human impact; land disturbance; dam construction; soil conservation; sand mining


New challenges in erosion and sedimentation research: a Chinese perspective

ZHAOYIN WANG1, LIJIAN QI1, GUOAN YU2 & CHENG LIU3

1 State Key Lab of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China [email protected]

2 Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China

3 International Research and Training Centre on Erosion and Sedimentation, Beijing 100048, China

Abstract Erosion may be classified according to the erosion agent into: water erosion, gravitational erosion, glacial erosion, and wind erosion (aeolian erosion). Complex erosion caused by two or more agents can occur in watersheds and river corridors, producing unique features and causing new problems. Earthquake erosion represents the mass movements caused by earthquakes. The volume of sediment mobilised by earthquake erosion may be 10–100 times greater than that for other types of erosion. Nevertheless, only a very small fraction (<0.2%) of the sediment from earthquake erosion will be transported over long distances and it may therefore have little effect on fluvial processes in large rivers. Grain erosion is a phenomenon involving the disintegration or breakdown of bare rocks under the action of insolation and temperature change, the detachment of the constituent grains by wind, the downslope flow of grains under the influence of gravity and the accumulation of the grains at the toe of the mountain forming a depositional fan. Grain erosion can result in airborne particles and cause injury to humans, and has resulted in numerous slope debris flows. More effort needs to be directed to developing control strategies. Neo-tectonic activity can trigger landslides and avalanches, which dam rivers and initiate intensive fluvial erosion. A landslide dam may develop into a knickpoint, if it is stabilized by the long-term action of the flow. Large knickpoints can totally change the fluvial processes and river morphology. Bed load motion in mountain streams is complex and the available bed load formulae are in many cases not applicable. The measured and estimated rates of bed load transport can differ by several orders of magnitude. The measured bed load transport rate in the Diaoga River can vary by as much as 1000 times under steady flow conditions, as a result of the dramatic difference in the incoming sediment load and different degrees of development of bed structures. New theories and new formulae for bed load transport in mountain streams are needed. Eco-sedimentation is a new challenge in sedimentation studies. The biodiversity of benthic invertebrates greatly depends on the stability and diversity of bed sediment. Pollutants in water may be adsorbed by suspended sediment and accumulate in the bed sediment bed. Benthic invertebrates can develop high concentrations of heavy metals due to their proximity to contaminated sediment. These new challenges represent new growth points of research on erosion and sedimentation in China and worldwide. Key words earthquake erosion; grain erosion; earthquake dams and lakes; knickpoints; bed load transport; eco-sedimentation


Agricultural activity as cause of aggradation of small Siberian rivers

VALENTIN GOLOSOV, NADEZDA IVANOVA & SVETLANA RULEVA


Laboratory of Soil Erosion and Fluvial Processes, Faculty of Geography, Moscow State University, GSP-1, Leninskie Gory, 119991 Moscow, [email protected]

Abstract Several examples of the influence of agricultural activity on small rivers of Siberia are discussed. A reduction of river net length has been observed in the western part of the agricultural zone of Siberia a few decades after an increase in the area of cultivated land. Two main factors influence the intensity of river aggradation: the decrease of underground runoff, and the increase in the transfer of sediment to the river channels. Evidence of channel aggradation can be found on rivers with catchment areas up to 22 000 km2, previously used for shipping. There is no simple relationship between the intensity of erosion on cultivated land and the rate of river net shortening, because of the difference in slope–channel connectivity and channel morphology. Climate fluctuations do not exert an important influence on the trend of river aggradation processes in the agricultural zone of Siberia. Small rivers draining intermontane depressions and the foothills of the eastern part of the agricultural zone of Siberia are less sensitive to increasing erosion rates within their basins. The higher gradients of their river channels contribute to the high transport capacity of these rivers and the wide river valley bottoms promote sediment redeposition in deluvial and proluvial cones. Evidence of aggradation of small rivers is not found in the eastern part of the Siberian agricultural zone, even in cases of extreme erosion within their basins, caused by a marked increase of precipitation in recent years.Key words small rivers; gully; erosion; channel aggradation; Siberia


Natural erosion rates and sediment delivery ratios in the Hilly Sichuan Basin, southwest China, since the Mid-Pleistocene

HONGWEI ZHU1,2, XINBAO ZHANG1,3, ANBANG WEN 1, YUNQI ZHANG1,2, YANGCHUN WANG1, YONGQING QI1,2 & XIUBIN HE1

1 Key Laboratory of Mountain Environment Evolution and Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, 610041 Chengdu, [email protected]

2 Graduate University of Chinese Academy of Sciences, 100049 Beijing, China3 State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences,

710075 Xi’an, China

Abstract The present hilly landforms in the Hilly Sichuan Basin above the Three Gorges have developed from the dissection of a large ancient fluvial plain as a result of the incision of the Yangtze River since the Mid-Pleistocene to form the Three Gorges. This paper reports a preliminary assessment of the natural mean annual erosion rate in the Xiaohegou Ravine, a typical small catchment in the Hilly Sichuan Basin, since the Mid-Pleistocene. The mean annual erosion rate is calculated by establishing the volume of material eroded from the zone between the original ancient plain surface and the present land surfaces, using a DEM. This is estimated to be equivalent to a surface lowering rate of 84 mm ka-1 or 211 t km-2 a-1 from the catchment over the last 0.715 Ma. The natural sediment delivery ratio is estimated to be 0.997. The precision of this estimate depends on the accuracy of the elevation data provided by the DEM. The maximum potential error for the estimated natural erosion rates obtained from this study is estimated to be 21.1%. Key words natural erosion rate; sediment delivery ratio; small catchment; Hilly Sichuan Basin, China; Yangtze River


Sediment load monitoring in the Mae Sa catchment in



northern Thailand

ALAN D. ZIEGLER1, LU XI XI1 & CHATCHAI TANTASARIN2

1 Geography Department, National University of Singapore, [email protected]

2 Kasetsart University, Bangkok, Thailand

Abstract This paper describes the development of an automated system to monitor total suspended solids (TSS) in the main channel of the Mae Sa River in northern Thailand. Logged discharge (Q) and turbidity (NTU) values were compared with hand-sampled TSS concentrations that were determined during six runoff events (n = 85 samples) and 13 other baseflow periods. Measured TSS values ranged from 10 to 7600 mg L-1, reflecting variable conditions between dry-season baseflow and wet-season stormflow. Because of hysteresis effects in the TSS versus discharge relationship, and high sediment concentrations that surpass the detection limits of the turbidity sensor during some storms, TSS was predicted best using multiple regression with both Q and NTU as independent variables. The estimated annual TSS load for 2006 is about 79 822 t, which is equivalent to a basin yield of 1076 t km-2 for the 74-km2 catchment. Key words total suspended solids; sediment sampling; turbidity monitoring; suspended sediment yield; erosion in the tropics; land-cover change


River sediment monitoring for baseline and change characterisation: a new management tool for the Ramu River Communities in Papua New Guinea

NICK A. CHAPPELL1, WLODEK TYCH1, PHIL SHEARMAN2,3, BARBARA LOKES2 & JOHN CHITOA4

1 Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK [email protected]

2 UPNG Remote Sensing Centre, PO Box 320, Biology Department, University of Papua New Guinea, Port Moresby, Papua New Guinea

3 School of Botany and Zoology, Australian National University, Canberra, Australian Capital Territory 0200, Australia4 Bismarck Ramu Group, PO Box 305, Madang, Papua New Guinea

Abstract The 18 719-km2 Ramu drainage basin has a water quality regime largely unaffected by mining operations. The Ramu River Communities believe that this may change over the coming months and years, and have initiated their own state-of-the-art monitoring of the main river. These observations have centred on high-frequency (10-minute) observations of turbidity and flow giving possibly the first such annual data at this sampling frequency on New Guinea Island. The first year of monitoring has demonstrated a marked seasonality in the delivery of suspended sediment from the 5866 km2 Upper Ramu basin, with considerably more natural variability in response within the 6-month wet season. Were new mining operations to release fine sediment (contaminated with heavy metals) into the watercourses of the Upper Ramu, then such shifts in the sediment signal may be more identifiable within the dry season. With evidence of an increase in fine sediment load, the Ramu Communities would have a more robust case to request increased monitoring of heavy metal levels within the Ramu, and if necessary to request improvements to the erosion and drainage management of mine areas.Key words mining; Papua New Guinea; Ramu; suspended sediment; turbidity



Placing sediment budgets in the socio-economic context for management of sedimentation in Lake Inle, Myanmar

TAKAHISA FURUICHI1 & ROBERT J. WASSON2

1 Center of Education for Leaders in Environmental Sectors, Tokyo University of Agriculture and Technology, 3-5-8 Saiwaicho, Fuchu, Tokyo 183-8509, [email protected]

2 Charles Darwin University, Level 4, Building 28, Casuarina Campus, Ellengowan Drive, Darwin NT 0909, Australia

Abstract In soil erosion and sedimentation research in developing countries, there is a need for scientists to direct increased attention to quantifying mechanisms and rates of sediment movement and objectively demonstrating their impacts. Soil erosion and sedimentation in the approx. 3800 km2 Lake Inle catchment, Myanmar have been of both local and national concern, given the significance of the lake to the economy, environment and culture. Sediment budgets that include a focus on different sedimentation rates in various sink environments around and in the lake were constructed for this lake catchment. The sediment budgets showed that deltas stored more than half of the sediment transported to the lake area, and that, despite the relatively smaller storage mass, the highest specific storage was found at river mouths. Socio-economic assessment identified diverse perspectives on the impacts of sedimentation. Of those perspectives, increasing difficulty in water transportation was recognized as a common, significant problem among stakeholders. Proposals for management of sedimentation therefore emphasize that priority should be given to controlling sedimentation at river mouths.Key words sedimentation; sediment budget; socio-economic assessment; Lake Inle; Myanmar


The changing rainfall–runoff dynamics and sediment response of small mountainous rivers in Taiwan under a warming climate

SHUH-JI KAO1, J. C. HUANG2, T. Y. LEE2, C. C. LIU3 & D. E. WALLING4

1 Research Center for Environmental Changes, Academia Sinica, Taiwan, State Key Laboratory of Marine Environmental Science, Xiamen University, Chinasjkao @ gate.sinica.edu.tw

2 Department of Geography, National Taiwan University, Taiwan3 Department of Earth Sciences, National Cheng Kung University, Taiwan, Taiwan4 Geography, College of Life and Environmental Sciences, University of Exeter, Devon, UK

Abstract A warming climate increases tropical cyclone intensity, causing more intense rainfall. This creates problems for soil and water conservation and management, particularly for countries in the western tropical-subtropical Pacific region, where cyclones (typhoons) frequently occur. Taiwan is located on a typhoon track and frequently suffers from devastating floods and landslides generated by typhoons. Here we present qualitative and quantitative evidence from Taiwan for the changing characteristics of rainfall–runoff patterns and the associated geomorphic response under a changing climate. We speculate regarding the impact of global warming on the hydrological cycle and associated processes and the threats posed to the inhabitants of the mountainous island of Taiwan. Key words rainfall; runoff; erosion; sediment yield; landslides; typhoon; Taiwan

________________________________________________________________

Sediment Problems and Sediment Management in Asian River Basins (Proceedings of the Workshop held at Hyderabad, India, September 2009). IAHS Publ. 349, 2011, 130-140.

Spatially-distributed assessment of sediment yield and shallow landslide potential area in the upper Citarum River basin, Indonesia

APIP1, KAORU TAKARA2 & YOSUKE YAMASHIKI2

1 Graduate School of Urban and Environment Engineering, Kyoto University, Kyoto 615-8540, [email protected]

2 Disaster Prevention Research Institute (DPRI), Kyoto University, Uji 611-0011, Japan

Abstract Frequently, only a few locations within a basin are critical and responsible for high amounts of soil loss due to surface soil erosion and shallow landslide events. In connection with sediment yield reduction programmes, effective control of soil losses requires implementation of best management practices (BMPs). For the effective and efficient implementation of BMPs, identification of such critical locations is essential. In this study a physically-based hydrological–geotechnical model was applied to an upland tropical basin, with the aim of providing an assessment tool for identification of critical sub-basins. The model consists of two primary components. These comprise a hillslope sediment–runoff component, which considers soil detachments by rain and surface runoff; and a stochastic slope instability algorithm. Daily streamflow and suspended sediment discharge data, as well as the spatial patterns of documented historical landslides, were used for model evaluation and application. Critical sub-basins were identified on the basis of spatially-distributed sediment yields and areas predicted as susceptible to shallow landsliding. The study demonstrated the high potential applicability of the proposed modelling approach for identifying areas vulnerable to erosion and thus important sediment sources. Key words soil erosion; slope instability; sediment yield; distributed model; critical sub-basins; Citarum River, Indonesia


Sediment yield investigations for controlling sedimentation in the catchment of the Sriramsagar reservoir, India

B. VENKATESWARA RAO1, K. SRINIVASA REDDY2 & P. RAVI BABU2

1 CEA&WMT, JNTUH, Hyderabad 500 085, India [email protected]

2 Centre for Water Resources, IST, JNTUH, Hyderabad 500 085, India

Abstract The high sediment yield of the catchment of the Sriramsagar reservoir in India is threatening the storage capacity of the reservoir. In this study estimates of sediment yield for three sub-watersheds obtained using a commonly-used prediction equation are compared with direct measurements. The sediment yield measurements were obtained by installing automatic water level recorders on the streams and by measuring the flow velocity using a current meter. Stream water samples were analysed in the laboratory to obtain the values of suspended sediment concentration required to calculate the sediment load. The sediment yields from the watersheds are also estimated using the Garde et al. equation, which employs parameters including a vegetative cover factor, slope, drainage density, annual runoff, annual precipitation and the area of the watershed. The measured sediment yields were in broad agreement with the estimated values, with the measured sediment yield for the three watersheds averaging 991.5 m3 km-2 year-1 and the estimated sediment yield averaging 813.3 m3 km-2 year-1 over the study period 2006–2008. In view of the need to reduce sediment deposition in the Sriramsagar reservoir, potential soil conservation measures are considered. Key words reservoir siltation; Sriramsagar reservoir; sediment yield; measurement; prediction; conservation measures


River sand mining and associated environmental problems in Sri Lanka

RANJANA U. K. PIYADASA Department of Geography, University of Colombo, Sri Lanka [email protected]

Abstract The demand for sand for construction purposes has increased significantly in Sri Lanka in recent years, particularly due to the tsunami disaster that occurred in December 2004. This high demand led to a major increase in sand mining in many areas. Extraction of sand from river bed and river bank sand deposits has increased greatly. The current demand for sand for building construction within the country is approximately 7–7.5 million cubic metres per year. River sand mining activities have disrupted the natural equilibrium and have caused adverse affects on the environment. The Nilwala and Ginganga rivers are the main rivers in southern Sri Lanka that are suffering from both illegal and excessive sand mining. However, other rivers in the southern part of the island have also been affected by this problem at different scales. It is estimated that mining of sand from the Nilwala River has increased by three times compared to 1997. Excessive extraction of sand from river channels results in wide ranging impacts, including the intrusion of sea water into the river, collapse of river bank, and loss of riparian land. Recognising the need for scientific assessments of the extent of environmental degradation caused by indiscriminate sand mining, an attempt has been made to study the environmental impacts of such sand mining in the Nilwala River basin of southern Sri Lanka and to propose corrective measures. The objective of the study reported in this contribution focused on changes in groundwater quality resulting from sand mining in the Nilwala River basin area. River sand mining has reduced significantly in recent years due to people participation, integrating research findings, imposition of legal regulatory frameworks, and networking of community-based organizations. Key words sand mining; salinity; pH; electrical conductivity; groundwater; seawater intrusion; Sri Lanka


Channel degradation in the Yangtze River after the impoundment of the Three Gorges Project

Y. T. LI & J. Y. DENGState Key Laboratory of Water Resource and Hydropower Engineering Science, Wuhan University, Wuhan, China [email protected]

Abstract The impoundment of the Three Georges Project (TGP) caused a major decrease in the sediment load downstream from the dam, and this inevitably resulted in channel degradation, which has important implications for flood control, navigation conditions and aquatic ecology in the whole river basin. Based on analysis of field data and mathematical modelling, estimates of the reduction in sediment load and the resulting channel degradation in the Yangtze River downstream from the dam are reported in this contribution. Comparison of the results of the current study with those of previous studies and with field data demonstrates that the model prediction of channel degradation in the Yangtze River after the impoundment of the TGP obtained in the current study conform more closely with the field data than previous predictions. Key words reduced sediment load; impoundment; the Three Gorges Reservoir; channel degradation; prediction



Assessment of reservoir sedimentation using remote sensing

SHARAD K. JAIN1 & SANJAY K. JAIN2

1 Indian Institute of Technology, Roorkee, [email protected]

2 National Institute of Hydrology, Roorkee, India

Abstract Efficient management of a reservoir calls for periodic assessment of its capacity. Hydrographic surveys of reservoirs provide valuable information on the rate and pattern of sedimentation, which is required for formulating measures to control sediment inflow and for optimum reservoir operation. Data from space platforms can play a significant role in reservoir capacity surveys. In the recent past, satellite remote sensing has emerged as an important tool in rapid, frequent and economical reservoir sedimentation assessment. Multi-temporal satellite data help in determining water surface areas for different water levels. Any reduction in the reservoir surface area at a specified water level over a time period is indicative of sediment deposition at and below that level. When integrated over a range of water levels, it permits the loss of storage due to sedimentation to be computed. Remote sensing techniques have been used to assess sedimentation rates in a number of reservoirs and the results are described in the paper.Key words reservoir; sedimentation; remote sensing; image processing; India


Sedimentation of reservoirs in Uzbekistan: a case study of the Akdarya reservoir, Zerafshan River Basin

SHAVKAT RAKHMATULLAEV1,2,3, FRÉDÉRIC HUNEAU2,3, MASHARIF BAKIEV1, MIKAEL MOTELICA-HEINO4 & PHILIPPE LE COUSTUMER2,3

1 Tashkent Institute of Irrigation and Melioration (TIIM), 39 Kary Niyazov Street, Tashkent, 100000, Uzbekistan2 Université de Bordeaux, UFR des Sciences de la Terre, B18, avenue des Facultés, 33405 Talence, France

[email protected] 3 Institut EGID, EA 4592 Géoressources & Environnement, 1 allée F. Daguin, 33607 Pessac, France4 Université d'Orléans, UMR 6113 CNRS/INSU, Institut des Sciences de la Terre d'Orléans, Campus Géosciences 1A,

rue de la Férollerie, 41071 Orléans, France

Abstract The major rivers of Central Asia (Amu Darya, Syr Darya and Zerafshan) are turbid watercourses. Thus many man-made water reservoirs are affected by high sedimentation rates. It is of strategic importance to rationally quantify available water resources in existing reservoirs to ensure a guaranteed water supply to the different water users. Recent drought years and physical deterioration of hydraulic structures urged authorities to re-estimate the water availability in reservoirs of Uzbekistan for the sustainable use of the scarce water resources and safe operation of hydraulic infrastructure. This paper presents the results after the application of a geostatistical approach to assess the water resources availability in the Akdarya reservoir of Uzbekistan. The geostatistical approach creates digital surfaces that represent relatively accurate reservoir bottom conditions and support automated reservoir volumes and surface areas calculations. This in turn significantly reduces time, work load and financial burdens for sedimentation survey projects.Key words water management; erosion; sedimentation; water reservoirs; bathymetric survey; geostatistics; volume estimation; Central Asia


Research on key technology for sediment management in large-scale reservoirs

DONGPO SUN1, MINGQUAN GENG2 & CHENG LIU3 1 North China University of Water Conservancy and Electric Power, Zhengzhou 450011, China

sundongpo @ ncwu.edu.cn 2 Yellow River Henan Bureau, Zhengzhou 450003, China 3 International Research and Training Center on Erosion and Sedimentation, Beijing 100048, China

Abstract The storage of the Xiaolangdi Reservoir on the Yellow River has been reducing rapidly due to sedimentation since the reservoir was commissioned. Experimental studies showed that discharging sediment with density currents at high water level was of low efficiency and the deposited sediment in the upstream part of the reservoir was difficult to discharge. Two methods of improving the de-silting capacity have been proposed, of which one is increasing the strength and transport capacity of density currents and the other is remobilising deposited sediment and pumping it out over the dam through special pipes. Both approaches require mechanical input to disturb and pump out the sediment. The authors propose a strategy to discharge fine sediment out of the reservoir by disturbing and pumping out the sediment using boats equipped with submersible pumps within an area 2–40 km in front of the dam during two periods of water-sediment regulation and power generation. This strategy can prolong the life of the reservoir and harmonise the relationship between the reservoir and the river.Key words reservoir; density current; sediment remobilisation; sediment removal; sediment pumping; siphon pipe; Xiaolangdi Reservoir


Sedimentation behind barrages and oblique river flow

KAPILESWAR MISHRA1 & DHRUBAJYOTI SEN2

1 Prajna Institute of Technology and Management, (PITAM) Palasa, Srikakulam, Andhra Pradesh, India [email protected]

2 Department of Civil Engineering, Indian Institute of Technology, Kharagpur, West Bengal, India

Abstract The waterways of many barrages are larger than required, due to overestimation of the design flood. The barrage gates are not completely opened except during the passage of the design flood, causing deposition of sediments and formation of shoals in the barrage pond. This results in the development of an oblique approaching flow towards the barrage and an increase in scouring due to a constricted waterway on both the upstream and downstream sides of the barrage. This paper presents examples of the present situation of sedimentation behind barrages and the incidence of oblique river flow, based on images obtained from the “Google Earth” virtual world model. Key words barrage; oblique flow; sedimentation; waterway; shoal development



Sediment dispersal processes and management in coping with climate change in the Meghna Estuary, Bangladesh

MAMINUL HAQUE SARKER, JAKIA AKTER, MD RUKNUL FERDOUS & FAHMIDA NOORCenter for Environmental and Geographic Information Services (CEGIS), House no.6, Road no. 23/C, Gulshan-1, Dhaka-1212, Bangladesh [email protected]

Abstract Due to flat terrain and dense population, the Bengal Delta is highly vulnerable to sea level rise. At present the delta building process is active in the Meghna Estuary. Information on sediment dispersal processes in the estuary and their response to different exogenic and anthropogenic forces is an important requirement for managing the sediment and developing adaptive measures to counter the potential impact of climate change. Historical maps, satellite images and tidal water level data were analysed and the response of the Meghna Estuary to extreme events, e.g. the 1950 Assam earthquake, as well as anthropogenic interventions, was assessed. The issue of sediment management was addressed, based on an understanding of the response of the estuary to the extreme natural event and anthropogenic interventions, along with an assessment of the response of the estuary to sea level rise. Among other interventions, emphasis has been directed to promoting vertical accretion by injecting sediment into polders.Key words Bengal delta; Meghna Estuary; sea level rise; sediment dispersal processes; vertical accretion; sediment injection

sediment problems and sediment management in …hydrologie.org/redbooks/a349/p349 description,...

Documents