Spatial Analysis Method On Digital River Channel Evolution

River bed terrain analysis the river geomorphology based is one of the main elements of the analysis of the river bed evolution analysis. With the development of GIS technology, qualitative and semi-quantitative analysis on the river bed evolution gradually transforms to the quantitative one. The purpose of this study is to establish the riverbed terrain analysis on the evolution of digital analysis system for the transition from traditional bed evolution terrain analysis methods to the digital one.This paper studied the spatial analysis methods on digital river bed evolution; the research mainly focused on the extraction method and analysis method of the riverbed thalweg, including raster DEM search, Closed contour endpoint act and section lowest point method. Raster DEM grid search method is to obtain the riverbed thalweg through a two-dimensional matrix search with a certain height rules. Endpoint closed contour mapping Method extracts thalweg based on manual riverbed thalweg line method; it extracts thalweg through endpoint from the contour lines and contour lines between the topological relationships. Section lowest point Method exacts thalweg based on the downstream section connecting line between the lowest points. Comparison and the synthesis of the three methods is canied out as wellIn riverbed evolution analysis, the establishment of the river bed as coordinate reference system evolution was proposed. The coordinate system provides reference for riverbed evolution with the river flows for rivers S axis and the vertical flow of the N-axis. Based on the Yangtze River in Jiangsu evolution of the situation, the establishment of the Yangtze River in Jiangsu baseline was proposed, and then applied in the Yangtze River in Jiangsu evolution analysis. Further, quantitative analysis on the thalweg models of the evolution of Zhenyang reach of Yangtze River, as well as the comparative analysis with the dynamic river axis, was realized.Through integrated use of the thalweg line method, the extraction results of the thalweg with various bed topography conditions are satisfying. With quantitative thalweg evolution analysis in rivers coordinate system, the accurate thalweg of planar and vertical displacement of erosion and deposition can be calculated. The application in the Yangtze River in Jiangsu Province and the analytic results on evolution of the river show that some quantitative results can be attained through this method.