390 / 2024-03-10 13:20:58

Investigation of bank collapse in the middle and lower reaches of the Yangtze River and recent changes in influencing factors of bank collapse

bank collapse; riverbank stability; investigation; influencing factors; middle and lower reaches of the Yangtze River

Subtheme 7: Sediment Regulation and Management > Topic 6: River- Lake Evolution and Ecology Rehabilitation

The main stream of the middle and lower reaches of the Yangtze River flows through a vast alluvial plain, with poor bank erosion resistance and drastic changes in riverbed erosion and sedimentation. Bank collapses used to occur frequently, seriously affecting the economic and social development along the river. According to survey statistics, since the Three Gorges Project was put into use for water storage, a total of 1049 bank collapses occurred in the middle and lower reaches of the Yangtze River from 2003 to 2022, with a total length of over 758.7km. The continuous implementation of bank protection projects has led to an overall decrease in the number of bank collapses in the middle and lower reaches of the Yangtze River in recent years, however, some sections of the protected banks still experience collapses from time to time. The main reason for this is that the collapse of riverbanks in the middle and lower reaches of the Yangtze River is influenced by various factors such as hydrodynamic conditions, river boundaries, and human activities. While in recent years, the influencing factors of riverbank collapse in the middle and lower reaches of the Yangtze River have undergone significant changes. Firstly, the continuous erosion of the river channel, especially the intensification of downcutting caused by nearshore riverbed erosion, increases the height difference of the bank and channel, and increases the possibility of bank slope instability. Secondly, the adjustment of local river regimes causes shifts in flow rushing points and changes in extent of mainstream adjacency to the banks, which can easily lead to erosion and collapse of the bank that has not received sufficient anti-erosion protection. Thirdly, during post-flood water-fall periods when water levels decrease significantly and rapidly, it creates a seepage pressure that is not conducive to the stability of the bank slope. In addition, during pre-flood water-rise periods when flow rate sharply increase, it is also easy to cause bank slope collapse due to the intensified erosion of the river bank by high-flow conditions.