A Study Of Delayed Response Of Water&Sediment Load Variation Impact On Bankfull Area In Jingjiang River Reach

The study of riverbed evolution of alluvial river is one of important contents inRiver Morphology. Under the interaction between floods and riverbed, the riverbedwill be self-adjusting and finally maintained equilibrium. As the erosion anddeposition of the riverbed needs a process, the riverbed will be delay its reaction toadapt the change of the river. Delayed response is a phenomenon that usually occursin fluvial processes of alluvial rivers. For many years, hydraulic engineers haveconducted a great deal of research work and some progress on self-adjustingmechanism of alluvial channels has been achieved. However, It is not enough tounderstand the delayed response mechanism of alluvial channels for the sake of theprevious study on riverbed evolution tended to put stress on stable states ofequilibrium, like the relationship between dominant discharge and hydro-geometricrelation. So it’s necessary to study the delayed response in self-adjusting mechanismof alluvial channels.This paper makes Jing-jiang river reach as the research object, which includesZhi-cheng station, Sha-shi station, Jian-li station and Cheng-ling-ji station, andbankfull area as argument to research the Delayed Response of water and sedimentload variation impact on bankfull area in the middle and lower reaches of the Yangtzeriver. By analyzing the delayed response of fluvial processes in alluvial rivers, wefinally establish the corresponding Delayed Response model, and suggestions forfurther research were proposed. The main conclusions of this paper are:(1) Jing-jiang reach is located in the middle reaches of Yangtze river. It isflowing through hilly, water development, water rich and low sediment concentration.The variation of incoming water and sediment is affected by reservoirs established inthe upstream regions.(2) According to analyzing the bankfull area of Jing-jiang river reach which candisclose the regularity of adjustment of riverbed in alluvial river, we drew the following conclusion that the phenomenon of delayed response of riverbed adjustmentin Jing-jiang river reach is real exist.(3) The delayed response model should be modified as the variation of incomingwater and sediment and the condition of channel boundary are different from that ofthe Yellow River basin. Research has shown that the modified model is more in linewith the real situation in Jing-jiang river reach. The correlation coefficient betweenthe measured and the computed has been greatly improved: the correlation coefficientof Sha-shi station has increased from0.46to0.54. Similarly, it is from0.1to0.6inJian-li station. The correlation coefficient of Cheng-ling-ji station is0.34.(4) According to modified the basic equation which deduced by LI lingyun forthe delayed response model, we establish the delayed response model for Jing-jiangriver reach. Finally, the variation of bankfull area in each station is predicted.