Analysis On Channel Deposition-Scouring Based On GIS

GIS is a new technology based on computer. With the study, development and application of the technology, a mixed science is formed, which is a system of managing and studying spatial data with the help of computer software, hardware. It can do with spatial data by geographical coordinates and spatial location, effectively manage data and study variant spatial entity and their correlation. Through overall analysis of redundant factors, information demanded can be acquaied swiftly. At the same time, the consequence can be shown with map, figure or data etc. In recent years, the main manners of spatial data management can provide corrdenging spatial knowledge for information management, pross control, science research, spatial decision ect. Thus, it is applied successfully in many fields to acquisite good economic and social benefits.With the development of GIS, the main procedure and concrete method can be presented for establishment of 3D surface of channel topography and surface analysis by using new GIS. DTM is the basic data of GIS, which is widely used in the design of route of railway, roadway, power line, area, volume and declivity calculation and intervisibility discretion between two points and random section drafting. Besides, it applied in hypsography to map contour, slope aspect chart of declivity and aerial perspectived drawing. Therefore, it provides advantage for variant procedure analysis based on 3D surface, for example analysis on channel scouring and siltation.The traditional methods for analysis on channel scouring and siltation is mianly sediment discharge quantity balance and topographic section mothod. They have low calculation accuracy, undistinct capability of spatial analysis in the practice because the two methods are limited by station distribution for stream-flow gauging and gauging skill, besides, because of the limitation of spatial analysis, a new method should be applied to analysis on channel scouring and siltation in order to ascertain precisely the distribution and change of channel scouring and siltation. The DEM technology is increasingly applied in the analysis on channel deposition - scouring. But it is impossible that keep the sediment on the cliff or the bank just because that the shaping of sediment can be imposed by hydraulic pressure and physical characteristic of sediment. Therefore, when analysis based on GIS technology, the restriction of the angle of repose should be considered when constructs DEM under water. So it is more precise to ascertain change and distribution of deposition - scouring and futher raising the credibility of measuring and reporting the sediment volume.In this paper,the main procedure and concrete method for establishment of 3D surface of channel topography by using GIS and for calculation and analysis of channel storage and changes in scouring and siltation are presented. Based on the powerful GIS software,which can be used as huge data input,spatial data analysis, TIN is generated considering the constrain of join of triangle side . On basis of this, the figure of flushing change can be drawn by comparing, analysising river plan, section change and channel capacity change. As a result, the localization of silt accumulation and flushing can be visualized. It facilities for analysis on regularity and trend of river process.All the topographical information of channel maps is utilized in the method,his precision of data acquisition and utilization efficiency to the mapping overtops terrain section method . With 3-D expression and spatial analysis ability,the whole calculation ,including map digitalizatiobe, 3-D surface production,channel detention calculation,analysis on scouring and siltation, section analysis can be finished in one system. Therefore ,it greatly improves work efficiency .The method has obvious advantages of higher calculation accuracy,visualized channel morphology and distinct capability of spatial analysis of scouring and siltation locations.Therefore,the method has not only higher value in th-eory,but also importance in practice,thus it will have huge value in generalizing.