Numerical Study of the Morphodynamic Response to a Macro-Scaled Sea-Crossing Project in Hangzhou Bay, China

Hangzhou Bay is a world-famous strong tidal estuary with an irregular coastline, unique topography, numerous human activities, and complex hydro-sedimentological environment. The Daishan-Yangshan Sea-Crossing Transport Corridor (DSTC) project is located at the mouth of Hangzhou Bay, which is composed of multiple sea-crossing bridges, an underground tube tunnel, and several man-made islands. The large-scale engineering of DSTC fully connects the cities of Shanghai, Yangshan, Daishan, Zhoushan, and Ningbo. This article discusses the morphodynamic responses due to the construction of the DSTC based on a state-of-art numerical model system from the perspective of its impacts on the hydro-sedimentological environment of Hangzhou Bay, as well as on adjacent projects. This study proved that the variation range of tide level in Hangzhou Bay is mostly within 2 cm after the implementation of the DSTC, while that of the man-made island and piers is only within 6 cm. The tidal prism decrease percentage of Hangzhou Bay is less than 0.5%. It does not significantly change the current field and underwater topography in Hangzhou Bay, except near the man-made islands and the bridge. The effect of the DSTC on surrounding ports and channels is small and limited. That is, the proposed DSTC engineering is feasible from the perspective of morphodynamic responses. The conclusions provide a useful reference for similar large-scale estuary construction projects.