九段沙上沙南沿坍塌与外沙内泓效应

利用1986~2013年的长江口海图以及2013年九段沙上沙南沿的冲淤观测数据,分析了外沙内泓地形形成机理以及凸显的效应。长江口深水航道治理工程改变了九段沙湿地局部边界条件,导致江亚南沙沙尾下延,深泓线北移,上沙南沿坍塌后退。建议采取护滩工程措施,保护上沙湿地资源。

Study on the collapse of upper Jiuduansha shoal and the effect of out-bar and inner channel

Basing on the bathymetric maps of the Changjiang Estuary surveyed from 1986 to 2013 and the field observed data of erosion in the upper Jiuduansha shoal, methods of GIS\\DEM and dynamic geomorphology are used to study the reformation mechanism and features of out bar and inner channel topography in the south part of upper Jiuduansha shoal. The results show that the local boundary conditions and regime of flow and sediment transport are changed by the Project of Deep Draft Channel of the Changjiang Estuary, resulting in northward drift of thalweg (-5 misobaths) strengthening of tidal current, in the Jiangya north passage, and continuous collapse and retreats in the upper Jiuduansha Shoal. Considering the paramount importance of the wetland, the local government should encourage conservation of the upper Jiuduansha shoal and take effective measures to protect the shoal.