Temporal and spatial changes in coastline movement of the Yangtze delta during 1974–2010

Abstract

The evolution of the Yangtze delta, where the largest economic zone (e.g. Shanghai) in China is located, directly affects the regional economic development and ecoenvironment. The mean high tide lines as the coastline delineated from multi-temporal remote sensing data of Landsat during 1974–2010 at intervals of about 8years were used to examine the shoreline progradation and recession of the Yangtze delta in the past four decades. Our results show that significant parts of the shoreline in the Yangtze delta in the past four decades and particularly after the operation of the Three Gorges Reservoir (TGR), the world’s largest hydropower project ever built, experienced continual progradation despite a substantial decrease in the Yangtze sediment input. During 1974–2010, the area of the Yangtze subaerial delta increased by 667km2 with a net progradation rate of 18.5km2/yr, and the maximum progradation occurred at the eastern parts of Chongming Island and Nanhui bank, where the coastline advanced seaward about 8 and 6km, respectively, with mean net progradation rates of 0.22 and 0.17km/yr, respectively. An important (probably dominant) reason for the Yangtze shoreline progradation despite markedly decreased riverine sediment supply is coastal engineering, such as sea reclamation works, filling project, and wharf constructions.