Recent evolution of Jiuduansha Shoal in Yangtze Estuary and its corresponding to engineering projects

The Jiuduansha Shoal is located in Yangtze Estuary of China and has attracted a lot of attentions with respect to its historical bathymetry evolution because it involves rich environmental resources. Based on the measured bathymetry data from 1997 to 2008, the digital elevation model of Jiuduansha Shoal was developed and used to analyze the recent shoal evolution. It is of particular interest to investigate its corresponding to engineering projects. Results show that from 1997 to 2008, the shoal area increased very slowly but the increasing rate gradually decreased, which is well correlated to the decreasing of sediment discharge due to dam construction at the upstream of Yangtze River. The deep-water navigation channel project in Yangtze Estuary has obvious effects on the nearby hydrodynamic condition and the morphology of the Jiuduansha Shoal. Remarkable deposition in north and erosion in south occurred at the middle and lower parts of the shoal. A 10.2 km long sand spit formed along the outer edge of the south jetty of the navigation channel project, which is due to both the jetty construction and the flow circulation in the North Passage.