Analyses on Temporal and Spatial Variation Characteristics of Erosion and Deposition in the Front Edge of Salt Marsh Wetland

Taking Yancheng Nature Reserve Salt Marsh as the research object, the remote sensing images from 2005 to 2020 were interpreted by using remote sensing and geographic information system technology. In this paper, the temporal and spatial variation characteristics of erosion and deposition in the front edge of salt marsh wetland were analyzed. The influence of sea level rise on the annual change of salt marsh area was analyzed. The characteristics of flow and sediment movement in salt marsh and the causes of erosion and deposition in front of salt marsh were analyzed. The results showed that: (1) During 2005-2007, the sea level was relatively low, and Spartina alterniflora in salt marsh expanded to the sea. Since 2007, the front edge of salt marsh wetland has coexisted with erosion and deposition. From 2008 to 2010, the front edge of salt marsh wetland once again showed a trend of comprehensive deposition to the sea side. From 2010 to 2012, the erosion of salt marsh wetland was serious. From 2012 to 2020, the front edge of salt marsh wetland in the range of 9 km south of Xinyang estuary was eroded. (2) The correlation analysis was carried out between the area of salt marsh wetland and sea level rise. Spartina alterniflora is easily affected by sea level change, owing to it having a low ecological niche. With the rise of sea level, the area of salt marsh has been decreasing since 2013. (3) In the front sea area of salt marsh wetland, the maximum velocity of the ebb and flood can reach the threshold velocity during the spring tide. The sediment starts to move at water depth of 10 m under wave actions. Owing to wave stirs up sediment and current transports the sediment, resuspended sediment causes the erosion of marsh-edge scarps.