DETERMINATION OF A TOPOGRAPHIC WETNESS INDEX USING HIGH RESOLUTION DIGITAL ELEVATION MODELS

Abstract

Topographic wetness indices (TWIs) computed from digital elevation models (DEMs) are means to forecast the amount of moisture in the soil. In this study, using sub-pixel/pixel attraction the spatial resolution of digital elevation models (DEM) was increased. In the attraction, model scale factors of (2,3,4) with two neighboring methods of touching and quadrant are applied to DEMs in Matlab software for the study area. The algorithm is evaluated using 148 sample points that were measured by the researchers. As a result, it was shown that a spatial attraction model with a scale factor of (S=2) gives better results compared to the scale factors greater than 2 and also touching neighboring are more accurate then quadrant. The results showed that waterway obtaining from DEM with high spatial resolution is more accurate than DEM 90m. So according to the results, it is suggested that the same model for increasing spatial resolution of DEM in the studies must be used. Furthermore, the results of TWI map with the new DEM extracting of attraction model as input data showed that TWI has more details from the moisture of soil than the TWI map prepared with DEM 90m.