长江口典型滩槽系统近期演变及河势控制对策探讨

Discussion on recent evolution of a typical channel-shoal system in Changjiang Estuary and measures for river regime control

近20 a来受长江入海泥沙锐减的影响,长江口滩槽系统发生相应冲淤调整,河势稳定面临新的挑战。选取长江口南支河段白茆沙和扁担沙滩槽系统为研究对象,分析了1997~2015年冲淤演变过程和主要特征。结果表明:白茆沙总体上冲刷萎缩,沙尾冲蚀消失,固沙潜堤工程的实施使得冲刷态势得到控制,但南北水道分流格局呈单向发展,南水道冲刷南靠,威胁太仓港岸线稳定;扁担沙处于自然演变状态,沙体局部出现切滩,沙尾不断下移并挤压新桥通道,影响南支总体河势稳定。基于此,提出了稳定白茆沙汊道分流格局,遏制扁担沙切滩和稳定新桥通道的河势控制对策。

In the past two decades,the channel-shoal systems of the Changjiang Estuary showed morphological response to the sharp decline of river sediment,so stability of the river regime is facing new challenges.The Baimao Shoal and Biandan Shoal in the south branch were chosen as the research object,and their evolution processes and main features from 1997 to 2015 were analyzed.The results showed that the Baimao Shoal experienced overall erosion and the shoal tail disappeared.The implementation of the sand-fixed submerged dike project controlled the shoal scouring.However the water diversion pattern of the southern and northern channels showed one-way development:the erosion and southward movement of the southern channel threatened the bank stability of Taicang port;the Biandan Shoal was under natural evolution state,the shoal incision and downstream accretion was observed,squeezing the Xinqiao connecting channel,which affected river regime stability of the south branch.Based on above results,the controlling measures were proposed,including stabilizing the diversion pattern of the Baimao Shoal system,suppressing the sand body incision of the Biandan Shoal and stabilizing the Xinqiao connecting channel.