GIS Analysis of the Natural Evolvement of the Hengsha East Shoal of the Yangtze River and the Infects of Projects in the Last Thirty Years

Based on the topographic materials collected before and after the first and second phases of the project that was aimed at improving the deep-water channel of the North Passage of the Yangtze River, this paperanalyzed the influence of the project on the erosion-accretion evolution of the Hengsha East Shoal, supported by the GIS and relative statistic software. The results show that the area of the Hengsha East Shoal has leveled off in the process of the natural evolvement, but since the last five years of 1990s, there has been a tendency for the shoal to decrease due to the decline of bedload from the Yangtze River. The north bank project of the deep-water channel has brought great changes to the erosion-accretion situation of the Hengsha East Shoal. The tidal channel of the Hengsha East Shoal became contorted and shrank; the Baitiaozi shoal and some low-water areas to its east accumulated sharply. With the siltation-promoting project brought into effect, conditions for silting are formed in Hengsha East Shoal. The siltation of the bedload flowing through this area and artificially blowing mud up to the shoal make the erosion of the Hengsha East Shoal speed up remarkably.