1984年以来长江口北支演变分析

Channel evolution in North Branch of Changjiang River estuary since 1984

根据1984～2005年实测长江口水下地形图,采用数字地形模型技术,从河势变化、河床纵横向调整、河槽容积变化等方面,分析了1984年以来长江口北支河床演变.围垦缩窄工程（尤其是口门处的围垦）对北支河床演变影响很大,削弱了径流量,改变了入流路线.北支主流线虽反复多变、滩槽变化频繁,但随着人工控导工程的实施,部分水域的主流线将在较长时间内保持稳定.北支已逐渐演变为涨潮流占优势的河道,河床总体演变以淤积萎缩为主,但其衰亡过程将经历较长时期.

Based on the measured underwater topographic map of the Changjiang River estuary from 1984 to 2005, the riverbed evolution in the North Branch since 1984 is analyzed by use of the digital topographic method in aspects of the regime variation, adjustment of longitudinal and cross section and channel-fill volume variation. The land reclamation and channel-narrowing works, especially the reclamation works in the entrance area, have great influences on the riverbed evolution in the North Branch by reducing runoff and changing water current route. The mainstream varies greatly in the North Branch, resulting in frequent changes of shoals and channels. t With implementation of artificial training works, the mainstream in some areas will keep constant during a long period of time. The North Branch has gradually transformed to a flood-tide channel, and sedimentation and channel shrinking will be the general evolution of the North Branch, but its decline process will take place for a considerable period of time.