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Wang Z.-Y.,Tsinghua University | Wang Z.-Y.,International Research and Training Center on Erosion and Sedimentation | Yu G.-A.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Huang H.Q.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Wang R.-Y.,Urbana University
International Journal of Sediment Research | Year: 2012

Deltas are the most dynamic part of large rivers and the characteristics of deltas reflect the basic nature of morphodynamics, ecology and anthropogenic influence. The authors investigated many deltas of large rivers, including the Yellow, Yangtze, Pearl, Rhine, Nile, Mississippi, Luanhe and Ebro rivers. Data were collected and sediment, water, benthic invertebrates and fish were sampled. Statistical analysis showed that deltas can be classified into male deltas and female deltas. The deltas of the Yellow, Mississippi, Luanhe, Ural and Ebro rivers are male deltas. Male deltas extend into the ocean, each with only one or two channels, forming a fan-shape. Its development process is accompanied with periodic nodal or random avulsions. Male deltas develop if the sediment load/water ratio is high and the tidal range is low. The deltas of the Yangtze, Rhein-Meuse-Scheldt, Pearl and Irrawaddy rivers are female. Female deltas consist of complex channel networks and numerous bars and islands. Female deltas develop if the load/water ratio is not high and tidal current is relatively strong. Female deltas provide stable and multiple habitats for various bio-communities. Therefore, the biodiversity of female deltas and the taxa richness of benthic invertebrates and fish are much higher than that of male deltas. Human activities reduced sediment load and change the delta gender from male to female. Male rivers have high levees in their lower reaches and estuary. Several rivers originate from the levees of a male river and flow parallel with the river into the sea. Appearance, persistence, length and stability of these rivers depend on the male river to which they are attached. Therefore, these rivers are named parasitizing rivers. In general, parasitizing rivers have no tributaries and almost no drainage area. The runoff of these rivers comes from the rainfall on the surrounding area, and therefore, the flow discharge exhibits very sharp peaks during rainfall. The Yellow and Luanhe rivers have many parasitizing rivers. Some of the parasitizing rivers are quite long, with a length of 400-500 km, such as the Tuhai River and Majia River. Management of parasitizing rivers must be integrated into management strategies of their father rivers. © 2012 International Research and Training Centre on Erosion and Sedimentation and the World Association for Sedimentation and Erosion Research.


Liu C.,International Research and Training Center on Erosion and Sedimentation | Wang J.,University of New Brunswick | He Y.,China Institute of Water Resources and Hydropower Research
Advances in Science and Technology of Water Resources | Year: 2013

To accurately evaluate variations of sediment loads in the Lancang-Mekong River and influences of its upstream hydropower development on sediment loads in its downstream reaches, the credible data of annual sediment loads at various monitoring stations along the Lower Mekong River are chosen from the existing literatures, and the annual runoffs and sediment loads at Gajiu hydrological station (the first station downstream Manwan Hydropower Station dam on Lancang River) from 1965 to 2003 are yielded. The change trend of annual sediment loads of the Lancang-Mekong River at various stations is analyzed and compared. The results show that the annual sediment loads at Gajiu hydrological station has a dramatical decrease of over 60% after the operation of Manwan Hydropower Project However, the sediment loads at Chiang Saen hydrological station and its downstream stations do not have the consistent change trend. The main causes for the less decrease of sediment loads at Chiang Saen hydrological station than that at Gajiu hydrological station are as follows; confluence of tributaries with high sediment concentration, soil and water losses caused by replacement of natural forest by artificial economic forest, and recovery of sediment content in the rivers. The amount of sediment loads of the Mekong River entering the sea is about 145 million t/a, and it is predicted to be reduced in the future.


Liu C.,International Research and Training Center on Erosion and Sedimentation | Liu C.,China Institute of Water Resources and Hydropower Research | He Y.,China Institute of Water Resources and Hydropower Research | Des Walling E.,University of Exeter | Wang J.,University of New Brunswick
Science China Technological Sciences | Year: 2013

Changes in the sediment load of a river can have important impacts on river channel evolution, nutrient fluxes, aquatic ecology and delta erosion and sedimentation, and the possibility of changes in the sediment load of the Lancang-Mekong River has attracted increasing concern in recent years. Existing studies present conflicting findings regarding the nature and magnitude of recent changes in the sediment load of the Lancang-Meking River and the authors have attempted to assemble the most reliable data on annual sediment loads for the period 1965-2003, to assess recent trends in the sediment load of the river. The changes in annual sediment load at 7 stations on the river are analyzed. Important sediment contributing areas are found in the reaches between Gajiu and Yunjinghong, Chiang Saen and Luang Prabang and downstream of Nong Khai. The sediment load increased at Gajiu, Yunjinghong and Chiang Saen over the period 1985-1992 because of serious soil erosion caused by the expansion of cultivation, the replacement of natural forest by plantations and land disturbance associated with hydropower dam construction. A marked reduction in sediment load occurred at Gajiu after the impoundment of the Manwan Hydropower dam on the Lancang River, but this reduction was not evident downstream at Yunjinghong and the stations further downstream. Significant increases in sediment load appeared at Mukdahan and Khong Chiam. These contrasting patterns of change reflect the influence of sediment contributions from the intervening catchment areas and channel systems as well as storage and remobilization of sediment from the channel system and the impact of hydraulic works such as irrigation systems. The long term mean annual sediment load of the Mekong River at its mouth is estimated to be ca. 145×106 t a-1, which is lower than previously reported values and it seems likely that this will be reduced in the foreseeable future. © 2013 Science China Press and Springer-Verlag Berlin Heidelberg.


Hu C.-H.,China Institute of Water Resources and Hydropower Research | Hu C.-H.,International Research and Training Center on Erosion and Sedimentation | Chen J.-G.,IRTCES | Guo Q.-C.,SKL WAC
International Journal of Sediment Research | Year: 2012

This paper studies relations between bankfull discharge, lateral cross section variation and the incoming flow and sediment condition in the Lower Yellow River using measured data from 1950 to 2003. Since 1950 the bankfull discharge has obviously decreased and the ratio of channel width to flow depth has increased. The critical annual average incoming sediment coefficient (defined as the ratio of sediment concentration to discharge) and discharge at the Huayuankou station are approximately 0.012 and 1,850 m 3 s -1, respectively, for no accumulative deposition occurring in the reach from Huayuankou to Lijin. On this basis, a mathematical model is used to study the scale of the main channel in the Lower Yellow River and its corresponding bankfull discharge under possible incoming flow and sediment conditions in the near future. The main factors influencing the scale of the main channel are analyzed, and measures to shape and maintain a medium-sized channel are discussed. The results show the effect of various water and sediment combinations released from the Xiaolangdi Reservoir on the shaping of the main channel and suggest that under recent incoming flow and sediment conditions, it is possible to shape and maintain a medium-sized channel with a bankfull discharge of approximate 4,000 m 3 s -1. © 2012 International Research and Training Centre on Erosion and Sedimentation and the World Association for Sedimentation and Erosion Research.


Liu C.,International Research and Training Center on Erosion and Sedimentation | Sui J.,University of Northern British Columbia | He Y.,China Institute of Water Resources and Hydropower Research | Hirshfield F.,University of Northern British Columbia
International Journal of Sediment Research | Year: 2013

Changes in runoff and sediment loads to the Pacific Ocean from 10 major Chinese rivers are presented in this paper. To quantitatively assess trends in runoff and sediment loads, a parameter called the "Trend Ratio T" has been defined in this paper. To summarize total runoff and sediment load from these rivers, data from 17 gauging stations for the duration 1955 to 2010 has been standardized, and the missing data have been interpolated by different approaches according to specific conditions. Over the observed 56-year study period, there is a quite stable change in total runoff. Results show that the mean annual runoff flux entering the Pacific Ocean from these rivers is approximately 1,425 billion cubic meters. It is found that all northern rivers within semi-arid and transitional zones including the Songhua, Liaohe, Haihe, Yellow and Huaihe rivers present declining trends in water discharge. Annual runoff in all southern rivers within humid zones including the Yangtze, Qiantang, Minjiang, Pearl and Lancang rivers does not change much, except for the Qiantang River whose annual runoff slightly increases. The annual sediment loads of all rivers show significant declining trends; the exceptions are the Songhua and Lancang rivers whose annual sediment loads have increasing trends. However, the mean annual sediment flux carried into the Pacific Ocean decreased from 2,026 million tonnes to 499 million tonnes over the 56-year period. During this time there were 4 distinct decreasing phases. The decrease in annual sediment flux is due to the integrated effects of human activity and climate change. The reduction in sediment flux makes it easy for reservoir operation; however, the decrease in sediment flux also creates problems, such as channel erosion, river bank collapse and the retreat of the delta area. © 2013 International Research and Training Centre on Erosion and Sedimentation and the World Association for Sedimentation and Erosion Research.


Wang Y.,International Research and Training Center on Erosion and Sedimentation | Qi M.,Beijing Jiaotong University | Jin Y.,Beijing Jiaotong University
Advances in Science and Technology of Water Resources | Year: 2016

In order to evaluate the influences of the bank boundary condition and the river dynamic condition on bank stability, through quantification of qualitative indices and standardization of quantitative indices, comprehensive evaluation functions for bank stability during the dry period and the flood period were created based on the hierarchical framework model and weight coefficients of the factors of bank failures, and a comprehensive evaluation method for bank stability, considering many factors, was put forward. The results of stability evaluation of three reach banks with different soil properties, bank boundary conditions, and river dynamic conditions show that the comprehensive evaluation function and method are suitable for bank stability evaluation. © 2016, Editorial Board of Advances in Science and Technology of Water Resources, Hohai University. All right reserved.


Chen J.-G.,International Research and Training Center on Erosion and Sedimentation | Zhou W.-H.,China Institute of Water Resources and Hydropower Research | Chen Q.,China Institute of Water Resources and Hydropower Research
Journal of Hydrodynamics | Year: 2012

The Xiaolangdi Hydro-Project is one of the large projects on the main stem of the Middle Yellow River. It has been operated for more than 10 years, since its impoundment in October, 1999. The reservoir has trapped 2.833×10 9 m3 of sediment, and caused the total erosion of 1.891×109 t in the Lower Yellow River from October, 1999 through October, 2010. Not only the serious atrophied situation of the Lower Yellow River (LYR) has been resuscitating, but also many new phenomena of sediment transport and behaviors of channel re-establishing are coming into being. They are illustrated and discussed in detail in this paper. © 2012 Publishing House for Journal of Hydrodynamics.


Du P.,International Research and Training Center on Erosion and Sedimentation | Du P.,University of Exeter | Walling D.E.,University of Exeter
Journal of Environmental Radioactivity | Year: 2012

Growing interest in the dynamics of floodplain evolution and the important role of overbank sedimentation on river floodplains as a sediment sink has focused attention on the need to document contemporary and recent rates of overbank sedimentation. The potential for using the fallout radionuclides 137Cs and excess 210Pb to estimate medium-term (10-102 years) sedimentation rates on river floodplains has attracted increasing attention. Most studies that have successfully used fallout radionuclides for this purpose have focused on the use of 137Cs. However, the use of excess 210Pb potentially offers a number of advantages over 137Cs measurements. Most existing investigations that have used excess 210Pb measurements to document sedimentation rates have, however, focused on lakes rather than floodplains and the transfer of the approach, and particularly the models used to estimate the sedimentation rate, to river floodplains involves a number of uncertainties, which require further attention. This contribution reports the results of an investigation of overbank sedimentation rates on the floodplains of several UK rivers. Sediment cores were collected from seven floodplain sites representative of different environmental conditions and located in different areas of England and Wales. Measurements of excess 210Pb and 137Cs were made on these cores. The 210Pb measurements have been used to estimate sedimentation rates and the results obtained by using different models have been compared. The 137Cs measurements have also been used to provide an essentially independent time marker for validation purposes. In using the 210Pb measurements, particular attention was directed to the problem of obtaining reliable estimates of the supported and excess or unsupported components of the total 210Pb activity of sediment samples. Although there was a reasonable degree of consistency between the estimates of sedimentation rate provided by the 137Cs and excess 210Pb measurements, some differences existed and the various models used to interpret excess 210Pb measurements could produce different results. By using the 137Cs measurements to provide independent validation of the estimates of sedimentation rate provided by the different models used with the excess 210Pb measurement it was shown that the CICCS and Composite CRS models appeared to generally provide the best results. © 2011 Elsevier Ltd.


Liu C.,International Research and Training Center on Erosion and Sedimentation | He Y.,China Institute of Water Resources and Hydropower Research | Chen J.,International Research and Training Center on Erosion and Sedimentation | Shi H.,International Research and Training Center on Erosion and Sedimentation
Advances in Science and Technology of Water Resources | Year: 2015

The amount of global fluvial sediment discharge to the oceans is an important and sensitive indicator, reflecting changes in the operation of the Earth, and has a significant influence on global socio-economic and environmental problems. Global river-to-ocean sediment flux has attracted the attention of many scholars around the world. Due to the lack of reliable and complete fluvial sediment load data, it is difficult to estimate the amount and variation of global fluvial sediment discharge to the oceans. There are large differences and inconsistencies between the values estimated by previous studies. In this paper, typical results obtained from 27 recently published papers in regards to the estimations of the global fluvial sediment discharge to the oceans are reviewed. The investigation shows that there have been large differences between estimates of the amount of global fluvial sediment discharge to the oceans in the early stages of such research, but, with increasingly in-depth examination, the estimated results in recent years have tended to be reasonable, with the amount mostly ranging from 12 to 20 billion tons per year. It is concluded that the amount of fluvial sediment discharge to the oceans before and after human activities can be considered 19 billion tons per year and 13 billion tons per year, respectively. ©, 2015, Editorial Office of Journal of Hohai University (Nature Sciences). All right reserved.


He Y.,China Institute of Water Resources and Hydropower Research | Liu C.,International Research and Training Center on Erosion and Sedimentation
International Journal of Sediment Research | Year: 2011

Sediment Oxygen Demand (SOD) is a key parameter for water quality analysis and for water quality modeling in rivers, lakes, estuaries and bays. The SOD can be measured both in the laboratory and in situ. However, the in situ technique appears to be the better approach for measuring SOD, as it likely to provide more representative and accurate results. In order to optimize the design of in situ SOD measurement chambers, the three-dimensional flow fields in cylindrical SOD measurement chambers, commonly used for in situ measurements, have been numerically simulated by using the RNG-based k-e{open} double equation turbulence model. SOD chambers with three different inflow pipe configurations were investigated. The results show that chamber III presents distinct advantages over the other designs for in situ SOD measurement, because good flow mixing can be achieved and bottom sediment suspension can be avoided in the chamber. The numerical simulation results were validated by comparison with existing results derived from laboratory experiments. The SOD measurement chamber designed to reflect the results of the numerical simulations was successfully tested for in situ SOD measurements in both fresh and saline waters. © 2011 International Research and Training Centre on Erosion and Sedimentation and the World Association for Sedimentation and Erosion Research.

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