洪枯变化异常条件下长江张家洲汊道演变特征OA

The Zhangjiazhou reach of the Yangtze River is a typical complex braided channel,and its evolu-tionary laws are crucial for navigation and flood control.Based on the hydrological data showing abnormal flood and drought variations from 2018 to 2024,combined with topographic data and regulation projects,this study analyzes the response mechanisms of river channel to extreme flood-drought conditions and human activities.During flood periods,the head of the sandbar undergoes severe erosion,resulting in an increased flow diver-sion ratio in the right branch and reduced inflow into the left branch;during dry periods,sedimentation in the left branch intensifies,leading to an increased flow diversion ratio in the right branch.The abrupt alternation between flood and dry periods triggers frequent switching of the scouring-deposition mode.The total sedimenta-tion of the river reach from 2018 to 2020 reached 12.05 million m3,and the total erosion from 2020 to 2024 reached 12.99 million m3.This has led to the formation of an asymmetric evolutionary pattern characterized by"enhancement of the right branch and decline of the left branch".Currently,the flow diversion ratio of the right branch during the dry periodis approximately 80％,posing a risk of branch imbalance.It is necessary to reinforce the erosion resistance of the revetment projects at the sandbar head and enhance monitoring to re-spond to changes in extreme hydrological conditions.