Study On Erosion And Deposition Trend Of Sandbank Based On Tidal Flats DEM

The process of landforms change over time has always been one of great attention in geography science.Though, study on erosion and deposition change of sandbank under different scales has achieved great success in the past thirty years, however, theory of erosion and deposition seasonal change is still not mature enough so far, it should be expanded at mechanism, data acquisition, and analysis methods. From the point of view of remote sensing and GIS, the exiting RS and GIS software also lacks of capability of space-time process analysis and dynamic simulation.Jiangsu radial sandbank is the most special depositional geomorphologic system among the coastal regions of China which is known by the special shape, complex and changeable terrain. It is a typical region for studying tidal current ridge. Under the support of GIS, RS, and spatial statistical, this study explores method which is to analyst erosion and deposition change of radiation sandbank, studies on erosion and deposition seasonal change, fits in with the requests of Jiangsu coastal development and strategy, has a strong reference for the research of tidal current ridge of Chinese coastal and other regions of world, provides background information for the profile study of muddy sandbank, also has important practical significance of guiding the orderly development and utilization of study area.This article selects Dongsha which has a large area in radial sandbank ridges as the study area, firstly, builds tidal flat elevation models by using waterlines picked up by multi-temporal RS images, takes multi-period tidal flat elevation model as data source, combines qualitative description and quantitative calculation, uses remote sensing and GIS methods to study the erosion and deposition variation trend of Dongsha, focus on the amount change of sediment erosion and deposition, the change of erosion and deposition rate, the change of erosion and deposition transport rate and the change of erosion and deposition transport direction, explores the factors that affect erosion and deposition seasonal changes. Study include:(1)Seasonal changes in the amount of erosion and deposition. Study takes DEM built by season as the data source, converts raster data into text files, delineates different contour lines with equal interval, separately calculates erosion and deposition area and erosion and deposition volume under different contour levels, and then calculates the amount of erosion and deposition, and finally analysts the regulations of seasonal change in the amount of erosion and deposition and its influencing factors.(2)Change of erosion and deposition rate. Take the minus operation using DEM which has been extracted, obtain raster data which represents the difference in value of DEM, focuses on the calculation of the "imaging time" of DEM, obtains the result of erosion and deposition rate, and finally analysts the change regulations of erosion and deposition rate and its influencing factors.(3)Seasonal change of erosion and deposition transport rate and direction. Firstly, the study takes the intersection operation and the minus operation using the DEM models, calculates gradient and gradient direction of the raster image which is represented the transport rate and transport direction, explores the display form of a diagram using transport rate data and transport direction data, so that clearly shows the change of erosion and deposition transport rate and transport direction, and finally analysts the regulations of seasonal change of erosion and deposition transport rate and transport direction and its influencing factors.The results of the study include:(1)The amount of erosion and deposition in autumn and winter is significantly higher than in spring and summer. The amount in spring is almost the same with it in autumn; the amount is lowest in summer. Seasonal changes in the amount of erosion and deposition are closely related with wing and waves, tidal range, tidal current, tidal creek systems and other factors.(2)The maximum point of erosion and deposition rate of the whole region is concentrated in the tidal creek densely area. Tidal flat has the trend of moving to the west north side.(3)The study area, There is the obvious convergence and dispersion phenomena of the transport direction. The region in which transport direction is convergence represents deposition. On the contrary, the region in which transport direction is dispersion represents erosion. Transport rate is large in the tidal creek densely area.