The Nanhui mudflat is located in the intersection area between the Yangtze River estuary and the Hangzhou Bay.It is controlled by two tidal currents from the Yangtze River estuary and the north coast of the Hangzhou Bay.In recent years,the tidal currents,sediment transport,morphological process of the Nanhui mudflat have changed significantly,which is mainly caused by the reclamation project of the low tidal flats.Based on the yearly measured bathymetry data (from 2006 to 2008) and 9 cross-sectional bathymetry data in each season from November 2007 to November 2008,combined with the sediment characteristics,we discuss the features of recent morphological process and interannual change in the Nanhui mudflat after the reclamation project and the hydrologic and sediment variations of the river basin,specially the seasonal scouring and silting characteristics.The results show that the annual erosion and siltation of Nanhui Dongtan is siltation,Nanhui South Beach is erosion.In different seasons of erosion and siltation in the Nanhui shoal,the process is different.In the plane,Nanhui beach isobath in winter and summer is mainly by silting,and in the spring and autumn,it is dominated by erosion.Vertically,the Nanhui Dongtan section in the spring,summer and autumn season is alternation of scouring and silting,it is silt in winter.Nanhui mouth section is scouring in autumn,and silt in winter and summer season.But Nanhui South Beach section is scouring in autumn and winter,silting in spring and summer.The sediment grain size of Nanhui east beach is generally finer.The median diameter of Nanhui mouth near the intersection of east and south beach is relatively coarse,and the median grain size of Nanhui south beach shoal is the coarser.