| The Changjiang River is the largest river in China, with a drainage area of 1.8×10~6 km~2.Wandering 6300 km eastward to the East China Sea, it contributes 9 ×10~11 m~3 of fresh water and 4.7 ×10~8 t of sediment into its estuary and the East China Sea each year. Meanwhile, GDP of the Changjang drainage basin accounts for 40% that of China. The Changjiang channel is well known as "Golden river channel" for it is one of the biggest river transport lines in China. However, the river channel in the middle Changjiang is affected strongly by sediment erosion and deposition, and flood disasters tends more frequent in the last century. River channel evolution has significant impacts on flood discharge, shipping and the sustainable development of Chanjing drainage basin. This has arisen numerous water conservancy projects that have been constructed in the Changjing River drainage basin during recent decades. Anthropogenic perturbations have caused considerable changes in water and sediment discharge movement. It is important to study the middle and low Changjiang river channel erosion-deposition evolution for integrate utilizing and exploiting the Changjiang river channel, and the river evolution is always international advanced research area of land surface integrant process.On the basis of the long-term historical discharge and sediment database, the present study firstly discussed seasonal variation of water and sediment discharge. The main results are as follows: 1) the water discharge and sediment load was increase before flood peak and decrease after flood peak. The rate of water and sediment increase is larger than the rate of water and sediment decrease in channel up Hankou station, the rate of water increase was smaller than the rate of water decrease in channel down Hankou station; 2) the suspended sediment particulate diameter was fine in flood season and was coarse in dry season. The riverbed particles were coarse in flood season and fine in dry season. Moreover, the suspended sediment and riverbed particles showed a decrease trend from upstream downward; 3) the wash load of suspended sediment concentration (SSC) in flood season was higher than that in dry season. The seasonal variation of bed load of SSC was just reversal while compared with the variation of fine suspended sediment; 4) it was positive correlation between water discharge and sediment load, and the value of correlation coefficient decreased from upstream downward; 5) the evolutionshowed siltation in dry season and erosion in flood season at Yichang-Xinchang channel section and the Luoshan-Hankou channel section, and the evolution showed reversal changes at Xinchang-Luoshan section and Hankou-Datong section while comparing with above river sections.Secondly, we constructed Digital Elevation Mode (DEM) of the middle and low Changjinag River channel and rationally simulated main river channel evolution on the basis of the Yichang-Wuhan River Relief Map in 1983 and 1997, and the Wuhan-Jiangyin River Relief Map in 1972 and 2002 (1:10000). This technology can quantitatively expresses temporal-spatial distribution of riverbed erosion-deposition such as cross-section profile, vertical profile, isobaths and erosion-deposition volume. On the other hand, based on classical hydrology dynamical theory, we made use of the field measured data, and studied the coupling interaction for water velocity and riverbed erosion and deposition, suspended sediment concentration and riverbed erosion, riverbed particles and the riverbed erosion and deposition. The main results were as follows: 1) 5159×10~8tons sediment were output from riverbed of Yichang-Wuhan river section from 1983 to 1997, and 3.83×10~8 tons sediment were output from riverbed of Wuhan-Jiangyin river section from 1972 to 2002, this riverbed erosion mainly resulted from increase dams construction; 2) the middle and low Yangtze River channel can be divided as follow sections. Yichang-Gongan erosional section, Shishou-Jianli depositional section, Shangchewan-Honghu erosional section, Luxikou-Wuhan depositio...
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