Research On River Bed Evolution Law Of Straight Braided Channel Under Clear Water Scouring Conditions

After the Three Gorges reservoir has been put into operation,a large number of silting reservoirs will cause water to drain.The river bed evolution process of a large number of branched rivers in the lower reaches of the reservoir will also respond accordingly.Therefore,the flood control,shipping and coastal economic development of the main stream of the middle and lower reaches of the Yangtze River should also face new changes and new patterns.It is of great theoretical and practical significance to conduct a study on the river bed evolution law of the three typical braided channels in the middle and lower reaches of the Yangtze River.In this paper,on the basis of the previous research results of the predecessors,by combining the statistical analysis with the model test of the measured data,the flow characteristics of the straight branched channel and the trend of the regulation of the river bed evolution under the condition of clean water scour are studied.The main contents of this paper are as follows:(1)through the analysis of the typical characteristics of the straight and straight branching channels in the middle and lower reaches of the Yangtze River,such as the plane morphological features,boundary conditions and the overall evolution,the typical features of the river and the east flow are analyzed.The river course,the historical evolution,the recent evolution and the evolution trend of the river course are analyzed and summarized..(2)through the fixed bed model test,the flow characteristics of the straight branched channel,including the water surface ratio drop,the surface flow field,the average velocity of the typical section and the variation of the flow power axis under different flow rates,are summarized.(3)through the dynamic bed model test,the difference in the deformation of the river bed during the series of sediment reduction years and the series of clean water is compared.On this basis,the evolution law of the river bed in the two series of straight branched rivers is compared and analyzed,and the reasons for the difference of the river bed deformation are preliminarily discussed.