Morphological responses in a meandering and island-braided reach of the Middle Yangtze River to the Three Gorges Reservoir impoundment  

作　　者：Dongdong Jia Xuejun Shao Xingnong Zhang Yongjun Lu Pengfei Hei 

机构地区：[1]State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Nanjing Hydraulic Research Institute [2]State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin,China Institute of Water Resources and Hydropower Research [3]State Key Laboratory of Hydroscience and Engineering,Tsinghua University [4]College of Life and Environmental Sciences,Minzu University of China

出　　处：《International Journal of Sediment Research》2016年第2期131-138,共8页国际泥沙研究（英文版）

基　　金：financially supported by the National Basic Research 973 Program of China (No.2012CB417002);the National Key Project of Scientific and Technical Supporting Programs funded by Ministry of Science and Technology of China (No.2012BAB04B03);the Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin (China Institute of Water Resources and Hydropower Research)(No.IWHR-SKL-201517);the National Natural Science Foundation of China (Nos.51109140,51579151,and 51209239);the Nanjing Hydraulic Research Institute Foundation (No.Y215015)

摘　　要：Lateral migration is an important form of morphological changes on the Middle Yangtze River （MYR）, particularly for the lower Jingjiang reach. The Three Gorges Reservoir （TGR） has substantially reduced sediment supply to the downstream river channels since its impoundment in June 2003. The scientific understanding of how decrease of sediment influences the processes of bank erosion and channel adjustments is complex and limited. In the present paper, the morphological responses in a typical meandering and island-braided river segment of the MYR to the filling of the TGR were investigated by a 3-D morphodynamic model. The potential of the 3-D model has been demonstrated by the observed data. The morphological evolutions in the Shishou bend during the first 12 years of the TGR impound- ment were predicted, The effects of the TGR operation on the planform evolutions in the study reach were analyzed based on the simulated results. Sediment load is decreased by 75~ due to the early filling of the TGR. The magnitude of bed degradation with less sediment load due to the TGR operation is increased compared with the pre-dam situation. Qualitatively, the overall planform evolution trends in the Shishou bend after the TGR operation are similar to that without the TGR operation. The magnitude of lateral migration has been increased in some part of the channel bend, where the morphological response of the TGR operation exhibits more lateral migration rather than vertical degradation. Scouring at the bank toe enhances bank failure. Decrease of sediment load and weak bank anti-scour ability as well as the significant helical flow can be responsible for intensified bank erosion in the channel bend.Lateral migration is an important form of morphological changes on the Middle Yangtze River （MYR）, particularly for the lower Jingjiang reach. The Three Gorges Reservoir （TGR） has substantially reduced sediment supply to the downstream river channels since its impoundment in June 2003. The scientific understanding of how decrease of sediment influences the processes of bank erosion and channel adjustments is complex and limited. In the present paper, the morphological responses in a typical meandering and island-braided river segment of the MYR to the filling of the TGR were investigated by a 3-D morphodynamic model. The potential of the 3-D model has been demonstrated by the observed data. The morphological evolutions in the Shishou bend during the first 12 years of the TGR impound- ment were predicted, The effects of the TGR operation on the planform evolutions in the study reach were analyzed based on the simulated results. Sediment load is decreased by 75~ due to the early filling of the TGR. The magnitude of bed degradation with less sediment load due to the TGR operation is increased compared with the pre-dam situation. Qualitatively, the overall planform evolution trends in the Shishou bend after the TGR operation are similar to that without the TGR operation. The magnitude of lateral migration has been increased in some part of the channel bend, where the morphological response of the TGR operation exhibits more lateral migration rather than vertical degradation. Scouring at the bank toe enhances bank failure. Decrease of sediment load and weak bank anti-scour ability as well as the significant helical flow can be responsible for intensified bank erosion in the channel bend.

关 键 词：Morphological changes The Middle Yangtze River The Three Gorges Reservoir Sediment transportBank erosion 3-D numerical simulation 

分 类 号：TV145[水利工程—水力学及河流动力学]