| As one part of the coastal zone, the tidal flat in the center of Jiangsu coast is an important area for productive activity of human. It is the largest sedimentary body of tidal flat which provides expansive space and abundant opportunity for the development of coastal areas in Jiangsu central coast. The evolution of the tidal flat in Jiangsu central coast is very important to ecological protection, tidal flat development and utilization, and the sustainable development of local society and economy. Therefore, the research on the terrain and evolution of the tidal flat in Jiangsu central coast is needed urgently. However, in the aspect of accessing tidal flat terrain, existing measuring methods are restricted because it is hard to acquire the high-accuracy, periodicity and large-scale terrain data, so that the deep research on the tidal flat evolution is difficult to progress.Based on the analysis above, making use of multi-temporal remote sensing images, this paper realizes the tidal flat elevation inversion of Jiangsu central coast, and on the basis of constructed Digital Elevation Model (DEM), this study reveals the temporal and spatial evolution of the tidal flat in the central Jiangsu coast in recent 40 years. The main contents of this research are listed as follows:(1) Tidal flats elevation inversion based on multi-temporal remote sensing images. By making use of Water Detection Method (WDM), sea level simulation and many other technology, this study realizes tidal flat elevation inversion of Jiangsu central coast and validates the accuracy of inverted DEM (horizontal accuracy:10 meters, vertical accuracy:decimeter). The accuracy shows that the result which is inverted by multi-temporal remote sensing images can be used for research on the evolution of tidal flat. On the basis of above,660 remote sensing images in different time are used to construct 17 DEM images of tidal flat in central Jiangsu coast between 1973 and 2010.(2) Erosion and deposition analysis of the tidal flat in the central Jiangsu coast. Based on the 17 DEM images, erosion and deposition evolution of tidal flat are analyzed. The result indicates that:the entire tidal flat in Jiangsu central coast is spreading and expanding toward the ocean, the near-land side of offshore sandbanks is constantly eroded, the other side is filled up ceaselessly. The net deposition of the entire tidal flat reached at least 1.13* 109m3 between 1973 and 2010. Deposited regions had connected gradually and formed a semi-circular arc topped by the south of western channal. For the tidal flat near the land, low tidal flat eroded constantly, and high tidal flat silted constantly, so that the intertidal zone was gradually narrowing.(3) Morphological evolution analysis of the tidal flat in Jiangsu central coast. Based on fractal dimension and standard deviation ellipse, analysis is maked for these regions:different coastal segments of tidal flat, Dongsha sandbank and Zhugensha sandbank. The result indicates that:the coastline near the land is tending towards flat and straight in nearly 40 years, including western bank of Dongsha, Niluohang and Zhugensha. Before 2006, Dongsha sandbank deflected counterclockwise, but deflected backswing after 2006. Zhugensha sandbank deflected counterclockwise in an early phase, and is getting into steady period of slow adjustment at present.(4) Sand cay evolution analysis of the tidal flat in Jiangsu central coast. This study focuses on the changes of barycentre of sand cay, and the result indicated that sand cays in outer fringe of the tidal flat are moving toward the sea, there are obvious regional changes in these movement, Dongsha sandbank moved continually eastwards, sand cays in north moved southwards, sand cays in east and south moved along the tidal channel outward, change intention varied with size or loacation of the sand cay. |
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