A bank erosion risk evaluation procedure based on the analytic hierarchy process and entropy weight method

Bank erosion is a key process of channel evolution in alluvial rivers, which can cause severe damage to riparian levees and influence the local river regime. Since the operation of the Three Gorges Project (TGP), the downstream reach has suffered continuous channel degradation and obvious bank erosion processes, putting great pressure on flood control management. A hybrid fuzzy procedure was thus proposed to evaluate bank erosion risk by combining the analytic hierarchy process and the entropy weight method, and this procedure was applied to evaluate the bank erosion risk in the Jingjiang Reach (JR) of the Middle Yangtze River. The Lower Jingjiang Reach (LJR) is a typical meandering channel, and the bank erosion is particularly serious. The weights of different influencing factors were firstly calculated by the proposed procedure, and the results showed that the dominant factor in the category of hydraulic factors was the curvature of the main flow (with a weight of 0.269), whereas the dominant factor in the category of boundary conditions was bank protection with the maximum weight of 0.378. Secondly, the occurrence possibility of bank erosion was presented using a linear function based on the calculated weights of different influencing factors. It was found that the river bank would be at a high risk as the bank erosion possibility was greater than 0.5; otherwise, the river bank would be at a low risk. The performance of the proposed procedure was evaluated by the measured bank erosion processes at two typical sections in the JR from 2003 to 2020, and satisfying results were obtained with an accuracy of 92%.