Abstract: Based on the hydrological and sediment survey datum in the spring of 2005 and the history sea charts, from the points of view on hydrodynamic condition, suspended sediment, sedimentary character, scouring and silting of the seabed, the evolution law of the seabed in the sea area of Nanhuizui and Qiqu Archipelago was analyzed. A trend of weaker silting and stronger scouring of this sea area in the recent 50 years was found, which is caused by the effect of ocean dynamics, the change of sediment flux to the sea and the constructions of some great coastal engineering projects.

Key words: Hangzhou bay, evolution of seabed, Nanhuizui, Qiqu Archipelago, sediment concentration, Yangtze estuary, Hangzhou bay, evolution of seabed, Nanhuizui, Qiqu Archipelago, sediment concentration