Recent Morphological Evolution of Jiuduan Shoal and Its Effect on Navigation Channel Sedimentation of North Passage in Yangtze River Estuary

On the basis of the field measurement data of hydrology,sediment and underwater topography,the evolutional process and mechanism of Jiuduan Shoal(JDS) in recent 10 years and its effect on navigation channel sedimentation of the North Passage(NP) are analyzed.The results are showed that JDS presents overall a feature of growing taller not bigger,i.e.the high shoal of elevation above 0 m is raising obviously,but the low shoal of elevation above 2m and 5m is stable.The higher beach of JDS is weakening its function of blocking sediment of South Training Dikes in the 2nd phase Deepwater Channel Project,and the rising tidal current with relatively higher sediment concentration on the beach face of JDS across South Training Dikes discharges into the middle reach of NP under certain condition of wind and waves,which would increase sediment sources of navigation channel sedimentation of NP in recent years.