Morphological impact of the construction of an offshore Yangshan Deepwater Harbor in the port of Shanghai, China

摘要

Yangshan Deepwater Harbor, located in the Qiqu Archipelago adjacent to Hangzhou Bay, is the new deepwater harbor of the Port of Shanghai. Its construction, which began in 2002, entails three types of engineering projects: closing a series of inlets, land reclamation, and dredging. After the construction of harbors 1, 2, and 3, these engineering projects caused a series of morphological changes in the area. Because of the serious sedimentation in the harbor area, further construction of the planned harbors has been stopped for the time being. Research on the sedimentation and its causes is urgently needed in order to decide whether to continue construction of more harbors. In this paper we analyze the morphological changes in the harbor area using bathymetric data collected from 1998 to 2010. Since 2004 bathymetry in the area has been surveyed every year, making it possible to analyze the spatial and temporal variation of sedimentationerosion in detail. The analyses provide a good insight into how the morphological changes are related to the various projects of the harbor construction and how the changes develop over time. It is shown that in the year immediately after an inlet was closed accretion occurred on both sides of the closure. The sedimentation rates decrease significantly in the following years. Accretion accelerated from 2007 to 2009 but decreased thereafter. The results of the analyses indicate that routine dredging will be necessary to maintain the requisite 15-m depth requirement for berths, but a regular dredging routine is feasible. For a better understanding of the mechanisms responsible for the observed morphological changes a numerical model based on Delft3D is used to simulate the hydrodynamic and sediment transport processes. The model results provide insights into how the morphological changes are related to the changes in hydrodynamics induced by the closures of the inlets.