Dem-based Hydrological Information Extraction And Applied Research

Extraction of hydrological information is one of the important parameters of distributed hydrology models and the key direction during the quantitative research based on Digital Elevation data (DEMs) in the traditional geomorphology as well. Furthermore, the landform of the earth surface controls the distribution of the substance and energy on the.surface, and impacts the hydrological, geomorphological and biological processes in the landscape greatly. Therefore, the research on the river network, and other hydrological information has important theoretical and practical significance. In this study, taking a certain drainage area as a case and using topographic maps with the scale of 1:50,000 as the data source, we analyze two important aspects in detail:Ⅰ,How to choose the grid scale during the conversion from special scale relief maps of one area to grid-based DEM.Ⅱ,How to choose the accumulated threshold of water flow when extract river network based on the grid DEM. On this basis, take this region as a case and calculate the cumulative amount of water flow in the region by adding weight raster data.This paper described the method of interpolating to creat grid DEM based on digital topographic map, analized the choice of cellsize when creat grid DEM based on digital topographic map. Based on the principle of geomorphology, to read all information and effective expression geomorphological features of base data as the goal, using information content analysis method to analyze the relationship of between DEM cellsize and extracted rms slope and determine the appropriate cellsize of creating grid DEM by interpolation in topographic map. Then randomly selected detection point on the created grid DEM and calculated RMSE to assessing the accuracy. And then compared the contours map extractied from grid DEM to the original contour map. Finally, introduce the algorithm of extracting hydrological information and extracting steps by ArcGIS based on grid DEM, and extracted river network by using the the corresponding point value on which the the accumulated threshold with the river network density curve tends to slow as a reasonable threshold. this avoid taking the mean of the flow accumulation in the watershed as the threshold only to get the best figure effect without consideration of the conversion of the geomorphological phenomena and so the better drainage network corresponding to the special scale terrain maps is derived from the perspective of the hydrology process and geographical spatial analysis. Finally, calculate the cumulative amount of water flow in this region by adding precipitation raster data as weight raster data.