The evolvement characteristics of Nanhuizui foreland in the Changjiang Estuary, China

The Nanhuizui is located between the Changjiang Estuary and the Hang zhou Bay,is the prolongation in the south of Changjiang River Delta.It is the main passage of runoff and sediment transportation into the Hangzhou Bay and southeast coast.With the abundant sediment supply of the Changjiang River and the extension of Changjiang River Delta to the sea,the sea bed of this area was continually deposited before 1990.Because of the decrease of sediment flux from the Changjiang River after the 1990s,the sea bed near the Nanhuizui is eroded instead of deposit.On the other hand,projects such as land making to accelerate the coastal deposit obstruct some passing sediment so that the erosion process has been speeded up.From now on,for some big projects in the Chang jiang Estuary are under construction,the sediment flux into sea will keep in a low level in history,then the sea bed will be eroded sequentially and this phenomenon should be recog nized by the related marine engineering departments.