Mechanisms for the evolution of double-convex cross-shore profile over accretional mudflats

Taking the accretional mudflats on the Jiangsu central coast as an example, a process-based morphodynamic numerical model is built.Mechanisms for the evolution of double-convex cross-shore profile are studied for the dominant long-shore tidal current and sufficient supplies of abundant sediments.The result shows that the flow velocity decreases sharply from the subtidal flats to the low waterline, and then decreases slowly landwards.The abrupt change in flow regime brings a high sedimentation rate along the low waterline, and forms the upper convex point in the area.During neap tides, the sedimentation rate will be greater than the erosion rate during spring tides over the middle subtidal flats, inducing a higher siltation rate.Furthermore, weak ebb current over the middle intertidal flats is unable to transport sufficient upwind sediment seawards, which induces a lower sediment concentration and a lower siltation rate over the upper subtidal flats during the final stage of ebb tides.Eventually, a low convex point will be formed over the middle subtidal flats.With the accretion of tidal flats, the levels of the upper and lower convex points will have a shift trend to high water level and low water level, respectively.Our results may not be in good agreement with other studies.More field observations are needed to support further researches.