The evolution characteristics of main waterways and their control mechanism in the radial sand ridges of the southern Yellow Sea

The comparison of the underwater topographic data in recent four decades shows that main waterways of the radial sand ridges area in the southern Yellow Sea tend to gradually migrate southward (scour depth and southward extension of the main channels in Xiyang, southward approach of Lanshayang Waterway and Xiaomiaohong Waterway on South Flank). Although there are various hypotheses about the cause and mechanism of the overall southward migration of the radial sand ridges, no universal and reliable understanding has been obtained so far. The mechanism of this process becomes a challenging problem which serves a key issue in the morphodynamics of the radial sand ridges and the harbor construction in this area. On the basis of the shoreline positions and underwater terrains at different development stages of the Huanghe Delta coast in northern Jiangsu Province, China since the northward return of the Huanghe River and flowed into the Bohai Sea, combined with the tidal wave numerical simulation study, the characteristics and hydrodynamic changes of the tidal wave system in the southern Yellow Sea at different evolution stages are investigated. It is shown that due to the shoreline retreat and the erosion of underwater delta, tidal current velocity is enhanced, and the enhanced area gradually migrates southward. It is revealed that this southward migration of a large-scale regional hydrodynamic axis is possibly a dominant mechanism leading to the overall southward migration of the radial sand ridges.