Sediment exchange between southern Yellow Sea and Yangtze River Estuary in response to storm events

Sediment exchange pattern between Yangtze River Estuary and southern Yellow Sea has been a crucial and controversial scientific question, which limits our understanding on the future prediction of morphological evolution of the radical sand ridges and Jiangsu tidal flats. This study investigates various processes including tides, winds and waves to identify a dominant factor controlling sediment exchange between the southern Yellow Sea and the Yangtze River Estuary under storm conditions using a validated numerical model. Our results show that tide is the dominant force controlling hydrodynamics and sediment transport between the two systems. Tide controlled residual currents and sediment fluxes are towards northwest from the Yangtze River Estuary to the southern Yellow Sea, while wind and wave-induced currents under normal wind condition (Beaufort 3 scale, 3.4m s-1) adjust net sediment flux by less than 10% and 40%, respectively. The influences of winds and waves on sediment transport vary with wind directions. South or southeast winds enhance the tide-induced northwestward sediment transport, while north or northeast winds reduce the northwestward sediment transport. Under strong winter storm condition, however, the associated northern winds and waves become more important than tides in sediment transport, leading to southeastern directed residual currents and net sediment fluxes. Sediment transport is more active in nearshore area than offshore areas, with little vertical variations.