Author(s): Wang Yanjun; Deng Caiyun; Lu Jinyou; Jin Zhongwu; Li Lingyun
Linked Author(s): Yanjun Wang
Keywords: Middle Yangtze River; Three Gorges Reservoir; Non-equilibrium adjustment process
Abstract: The study of the water and sediment transport, river morphology adjustment mechanism caused by human activities, especially the construction of large reservoirs, is of great significance for maintaining the health of river system and realizing the sustainable development of river basin. After the impoundment of the Three Gorges Reservoir (TGR), due to a sharp decrease in the sediment load entering the middle reaches of the Yangtze River (MYR), the river channel downstream of the TGR have changed from the relative equilibrium of erosion and deposition to a long-term and long-distance erosion, leading to an important impact on the flood control and eco-environment safety. Therefore, it is urgent to carry out the research on the response adjustment process and the relative equilibrium state prediction of the riverbed morphology in the MYR. Based on the measured discharge, sediment load, water stage, and erosion and sedimentation data from the MYR, the response process of different channel morphological variables to the operation of the TGR is analyzed. Moreover, a generalized model for the quantitative simulation of its geomorphic adjustment is proposed by using the existing theoretical model of the accumulation processes of internal feedback induced by external disturbances. Results show that the response adjustment rates of the different channel morphological variables, including the cumulative erosion per unit river length, low-flow channel area and the fall values of water level at 10000 m3/s discharge, over time are relatively fast in the early period following disturbances but then slow down rapidly. The non-equilibrium adjustment process can be accurately described by this theoretical model, since the corresponding calculated values of the different morphological parameters were in good agreement with the measured values, the coefficient of determination (R2) between them remain at around 0.96. The attenuation coefficient of response intensity α of the model decreases downstream the channel, which is subject to the response law of the river morphology to the external disturbances that the response is earlier in the upstream than in the downstream and it continues to develop to the downstream.
Year: 2024