On the open coast of the Changjiang Delta, waves temporally play their dominant roles in shaping the tidal-flat profile,especially during typhoons. Detailed analyses are presented of the variations in grain sizes of surface sediments and bedlevel, measured in the summer of 1999 at Nanhui mudflats, south flank of the Changjiang Delta, China. Cross-shorevariations in bed level are distinctly site-specific in response to waves. The site-specific erosion rates are related to localwater depth, sediment properties, vegetation, and exposure time per semidiurnal tidal cycle. A great difference existsbetween the higher and lower intertidal mudflats bordered at the mean sea level (MSL): the higher section is dominated bycontinuous accretion, while the lower section is characteristic of dynamic changes in erosion and accretion phases. Swellsplay their more important roles in shaping the profile than local wind-driven waves at the study mudflat, where swellspropagate onshore without great barriers’ damping and local winds are not highly strengthened by distant typhoons.Storm processes are greatly modulated by tides. The magnitude of erosion is greater by a weak storm during spring tidesthan a strong storm during neap tides. Significant changes in entrainment capacity of tidal currents from neap to springtides account for the different erosion and accretion models of the intertidal mudflat.