Beijing, China (July 12):The second issue of the International Journal of Sediment Research published with new cover design. The contents of theJournal include 8 technical papers. All the founding memebers and new members of WASER will receive a complimentary copy of the Journl via surface mail. Claims for missing issues will be honored free of charge within fourth months. The abstracts of the technical papers are as follows:

Volume 20 Number 2 June 2005

Technical Papers

Discontinuous Flow of Turbid Density Currents. II. Internal Hydraulic Jump

Jiahua FAN 81-88

ABSTRACT

Traveling and stationary internal hydraulic jumps in density currents with positive or negative entrainment coefficients were analyzed based on simple assumptions. An expression of internal hydraulic jumps with entrainment coefficients was derived. Experimental data, published in literature, of stationary internal hydraulic jumps in turbid, thermal and saline density currents including measured values of water entrainment were used to compare with theory. Comparison was also made of traveling internal hydraulic jumps between measured data and theory.

Key Words : Density current, Turbidity current, Discontinuous flow, Stratified flow, Internal hydraulic jump, Water entrainment

Characteristics of Sediment Transport a long a River Reach w ith a Reservoir

Jueyi SUI, Peter JACKSON , Cheng LIU , Daxian FANG and Jun WANG 89-101

ABSTRACT

Based on long-term measurements at three gauging stations , Toudaoguai, Fugu and Hequ, and one meteorological station, this article discusses the features of discharge (Q) and sediment concentration ( C S ) of a river reach of the Yellow River with a reservoir located in the Loess Plateau. The impacts of the local sub-watershed between Toudaoguai and Fugu gauging station s on sediment budget to the Yellow River have been analyzed. In addition, the deposition processes in the Tianqiao Reservoir have been investigated. Results show over 80% of the precipitation that falls in the local sub-watershed is unable to contribute to the Yellow River runoff process . It is found that the annual maximum sediment concentration is usually less than 30 kg /m 3 during flood seasons at Toudaoguai Gauging Station, but the sediment concentration varies dramatically at Fugu Gauging Station. About 35% of the sediment eroded in the sub-watersheds between Toudaoguai and Fugu gauging station s was produced from the Huangfuchuan sub-watershed which has a drainage area accounting only for 10% of the drainage area between Toudaoguai and Fugu gauging station s . The Tianqiao Reservoir generally has deposition during the summer flood season, and scouring during the non-flood season. On average, over 85% of deposited sediment in the reservoir occurs in the 12 km long lower reservoir reach. The volume of annual deposition in the reservoir mainly depends on the volume of water from the local region between Hequ and Fugu gauging station s.

Key Wards: F lood season, Huangfuchuan River , Loess Plateau, Reservoir storage capacity, Runoff depth, Sediment concentration, Sediment deposition, the Yellow River , Tianquao Reservoir

Fluvial Processes in the Lower Jingjiang River : Impact of the Three Gorges Reservoir Impoundment

Xuejun SHAO, Hong WANG and Zhaoyin WANG 102-108

abstract

Sediment supply to the lower Jingjiang River will be subject to substantial reduction after the impoundment of the Three Gorges Reservoir, which could result in an excess of carrying capacity and serious bank erosions in the downstream alluvial channel, threatening the bank protection works and the safety of the Jingjiang Dyke . This paper presents a summary of research works concerning th e fluvial processes in the lower Jingjiang River and the possible impact of the Three Gorges Reservoir impoundment on the variation of its channel pattern . Three different predictions have been put forward by researchers: 1) the Jingjiang River will evolve towards a more sinuous, meandering channel pattern, with extensive bank erosion taking place along the river; 2) the river channel will be straightened and broadened because no point bar can be formed due to reduced sediment supply while bank erosion develops in the concave bank, and 3) this river reach will maintain its present channel pattern without significant change, although the sinuosity may be slightly reduced, since: a) the Three Gorges Reservoir mainly intercept sediment particles with size s larger than 0.025mm , and b) the complex interaction between the Yangtze River and the Dongting Lake helps to reduce the negative effect of channel erosion through certain self-adjusting mechanism in fluvial processes. Discrepancy between these predictions shows that further research efforts are needed to understand the impact of Three Gorges Reservoir operation on the downstream fluvial processes. Meanwhile, there is an urgent need to closely monitor future development in the fluvial processes of the Jingjiang River and its influence on the safety of the Jingjiang Dykes.

Key Words: Three Gorges Reservoir , Downstream impact , Fluvial processes , Yangtze River

The Operation Mode of “Storing the Clear Water and Discharging the Muddy Flow” for Reservoirs Built on Heavily Silt-Laden Rivers—— A Case Study of the Sanmenxia Reservoir

Wenxue LI, Yuanfeng ZHANG and Cuiping ZHANG 109-116

ABSTRACT

Observation of the operation of the Sanmenxia Reservoir on the Yellow River has led to the conclusion that to preserve a certain effective storage volume for reservoirs built on heavily silt-laden rivers is feasible if the reservoir is operated according to the principle known as “storing the clear water and discharging the muddy flow”. The relative stability of the bed elevation at the end of the backwater and the reservoir's erosion and deposition equilibrium depend on the compatibility of the pool level maintained in non-flood seasons with the conditions of flow and sediment load during flood seasons. Operating the reservoir to regulate the flood and sediment load during flood seasons can reduce the rate of aggradation in the Lower Yellow River . The basic condition for applying the operation mode of “storing the clear water and discharging the muddy flow” is that a sufficient amount of water should be used for discharging sediment during flood seasons. Under the condition of extremely low flow years, reservoir sedimentation cannot be avoided even if this operation mode is adopted.

Key Words: Reservoir, Sedimentation, The Yellow River , Operation

Use of S urface G uide P anels as P ier S cour C ountermeasures

Chin-Kun HUANG, Chii-Jau TANG and Ting-Yuan KUO 117-128

Field Observations on B ed S ediments and S andwaves in C hangjiang E stuary

Jiufa LI, Xinning WAN, Xiaohua CHEN and Ming YING 129-135

Abstract A series of advanced instruments were applied to obtain the field data of bed, bed forms and relevant dynamic factors in the 150 km -long reach of the Changjiang River from Jiangyin to Hengsha Island in March 2002. We found that well-sorted fine sand was in the majority of the bed sediment, which had a median diameter of 2 φ . Well-developed sandwaves were formed because the grains jumped together on the bed, which was related to the granularity and current velocity during the flood-ebb tidal cycles.

Key w ords : Changjiang estuary, Sediment, Bedload transport, Granularity, Sandwave

Downslope Erosion Process under Upslope Runoff and Sediment Using a Dual-Box System Peiqing XIAO, Fenli ZHENG and Wenyi YAO 136-142

Transport of Gravels with Different Ranges of Grain Sizes in a Steep Channel

Jau-Yau LU and Chih-Chiang SU 143-155

ABSTRACT An understanding of the transport mechanism of gravel-bed rivers is very important for the river management and engineering works. The main objective of this study was to conduct a series of laboratory experiment in a steep flume to investigate the particle segregation and the transport rate of nonuniform gravel. Median sizes of 15 mm and 7.5 mm , and gradation coefficients of 1.5 and 2.0 were selected for the particle size distributions of nonuniform gravel. In addition to the 36 sets of data collected in this study, 635 sets of existing data for gravel with both nonuniform and nearly uniform sizes were analyzed. According to the results of the sieve analysis and the related theory, hiding functions for both particle size distributions of this study were derived. An attempt was made to develop an Einstein-type transport relationship for nonuniform gravel using dimensionless parameters with mean size as a representative particle size. A modified Schoklitsch-type sediment transport equation with a critical unit flow discharge was also developed to reasonably predict the transport rate of gravels. In addition, an artificial neural network (ANN) model with a back-propagation network (BPN) algorithm was also applied in this study.  

Key Words: Sediment transport rate, Bed load, Steep flume, Nonuniform gravel, Particle gradation, Hiding phenomenon, Back-propagation network, Artificial neural network

Cover Photo: A Physical Model of the Yellow River

Sponsor: World Association for Sedimentation and Erosion Research (WASER)

Editied by: International Research and Training Center on Erosion and Sedimentation (IRTCES)

Editors: Z. Y. Wang , Sam S. Y. Wang, J. J. Zhou, B.S. Wu, W. H. Graf, T. Takahashi,

D. Knight, C. S. melching

Publisher: IRTCES, China
Distributer: IRTCES, China