Tidal flat stability analysis based on GIS RS technology: A case study in Dongsha sandbank, offshore the coast of Jiangsu province

摘要

Stability of the tidal flat in silt-muddy coast is the ability to keep its terrain from erosion under the ocean dynamic processes. Evaluating the stability of the tidal flat is one of the most important issues insediment dynamics research field , and has been attached more and more importance. Dongsha Sandbank is one of the largest sandbanks of the radial sand ridges, and serves as an important barrier to the inner sandbank and has a direct impact on the process of Tiaozini Sandbank merging into mainland. To evaluate the stability of Dongsha Sandbank will provide guidance for coastal zone environmental protection (such as environmental protection and coast protection, etc.) to make a rational use of tidal flat resources for sustainable development. In the study, 63 scenes of remotely sensed imageries from 1973 to 2007 were collected, taken by different sensors such as MSS, TM, ETM+, SPOT, ASTER and CBERS. GIS & RS technology was used in the stability analysis of Dongsha Sandbank tidal flat based on field investigation, RS classification and overlay analysis. Major relate factors such as sediment dynamic environment, tidal channel and tidal creek system were discussed in the paper. Some conclusion can be summarized as follows :( 1) Integral stability of Dongsha Sandbank tidal flat has been gradually declined from 1973 to 2007. This trend was embedded in two aspects: both area of stable tidal flat and maximum value of stability coefficient degraded. (2) Tidal flat with high stability is mainly distributed on the sand ridges of Dongsha Sandbank, and has an integrally contractive trend: in the mid-continental region, one region with high stability coefficient has been broken into two small parts- the northern part has a southwards movement while the southern has a northern wards movement; within the north part, stability of the tidal flat reduced with the northwards movement of the shoreline; in the west part, the tidal flat is in an unstable state due to the lateral swing of Xiyang Tidal Channel and strengthen of tidal creek activity; and in the south part, the tidal flat has a low stability due to the unstable flow path of Doufuzhayaomen Tidal Channel.