Analysis of the evolution on tidal flat and their reasons in Dongsha based on remote sensing

The tidal flat changes of Dongsha sandbank across the West Ocean are severely influenced by Dafeng Port Construction and the large-scale activities of reclaiming land from seawaters around it. Dongsha sandbank is the second largest one with highest elevation among the radial sand ridge system offshore Jiangsu Province, so the research on the changes of the western tidal flat of Dongsha sandbank is extraordinary helpful to the evolution recognition of the radial sand ridge system offshore Jiangsu Province and the adjacent tideland. This paper applies remote sensing technology to conduct dynamic monitoring on the diverse and complex topography of tidal creek system at the western tidal flat of Dongsha sandbank, and acquires a rapid and effective result of surface information. Also this paper defines the average low tide line, which can represent the geomorphic characteristics changes of tidal flat. The average low tide lines of several representative years, which can indicate the variation of erosion and deposition at the western tidal flat of Dongsha sandbank, are extracted on the high resolution remote sensing images. Conclusion: the changes of water dynamic environment due to the massive coastal engineering contributes to the worsening erosion at the western tidal flat of Dongsha Sandbank, between 2006 and 2008, the average low tide line receded 81m on average; between 2008 and 2009, and it receded 285m on average; The entirety of the western tidal flat in Dongsha assumes a strong tendency of retrogradation towards the East.