Dynamic evolution analysis of Dongsha shoal of the radial sand ridgds in South Yellow Sea from 1973 to 2016

The Dongsha Shoal, a part of the radial sand ridges off the Jiangsu coast, is selected as a case in this paper to study the dynamic evolution of the ridge system. Based on the remote sensing images from 1973 to 2016, the concepts of minimum enclosing rectangle and centroid in morphology are introduced to reveal the general moving trend of the shoal. The centroids of minimum enclosing rectangles of each phase are extracted by means of ArcGIS10.2. The general moving trend of the Dongsha Shoal is specified by comparison of the centroids in different stages. The factors affecting the movement of Dongsha shoal is further studied with the data of nori-planting and records of tropical cyclones. The results suggest that the Dongsha Shoal has been moving toward north and northeast in the past 43 years. It can be further divided into five specific phases. The moving directions and speeds in each phases are different. Data shows that the impact of tropic cyclones is increasing in the Dongshan Shoal. The nori-planting in Dongsha Shoal expands currently, of which the impacts on the sand sediment at the Dongsha Shoal requires further researches.