Channel evolution in North Branch of Changjiang River estuary since 1984

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.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.