Extraction And Application Of Topographic Wetness Index Based On DEM

Topographic wetness index, with easy extraction and definite physical basis, has been applied to simulate and predict the spatial distribution of soil water and runoff widely, while the research and application of topographic wetness index on the Losses Plateau are still insufficient. Based on the past research, this study reviewed the development and application of the topographic wetness index, analyzed the establishment of DEM with the optimal resolution using ANUDEM, proposed the appropriate method for extracting the topographic wetness index from DEM, and evaluated the application of the extracted topographic wetness index to describe and understand the spatial distribution of soil moisture at the Xiannangou and Zhifanggou Catchment which both are typical catchments of the Loess Hilly and Gully Area. The main results and conclusions mainly included,1. Establishment of DEM with the optimal resolution at Xiannangou Catchment. Based on the digital topographic map (1:10000) of Xiannangou Catchment and ANUDEM software, the three important parameters of ANUDEM, which are the optimal resolution of DEM, the second roughness penalty and the number of iterations, are identified as half contour interval, 0.8 and 20-30times respectively. With the quantified parameters, the DEM with optimal resolution is established for the extraction of topographic and hydrological factors. Meanwhile, the method of Information Content Analysis can be applied as a general method to identify the optimal resolution of DEM in hydrological research.2. Evaluation of DEM quality. For the DEM of Xiannangou Catchment established with ANUDEM, the fake sinks are few, the derived contours form the DEM are matched well to the originals, the biggest absolute error is less than one contour interval(5m) and the biggest RMSE is also lower than 1/3 contour interval, which reach the third class of the U.S.G.S grading standards. Compared with TIN method, ANUDEM method is simpler and easier to apply in hydrological analysis because the surface of the DEM is smoother without plane triangle, the streamlines are continuous without parallel lines, which are the inherent disadvantages for TIN method.3. Extraction of topographic wetness index. The simple index, the index integrated with aspect of slope, the index integrated with land use and the index integrated with both slope aspect and land use, are extracted from the Zhifanggou's DEM from aerial photograph and...