Application of DEM to Identify the Infiltration Zones Using GIS

Abstract

Drainage networks are usually digitized from the existing topographic maps using GIS. Unfortunately, this method is expensive and time consuming. But, nowadays, automatic extraction of drainage network from Digital Elevation Model (DEM) with the help of GIS has become possible and used for hydrological studies. DEM consists of a sampled array of elevations for a number of ground positions at regularly spaced intervals. It is a storehouse of a variety of hydrological information along with terrain characteristics and valuable in groundwater system analysis. In this paper, the contour maps with 20 m vertical intervals were digitized to create DEM data and drainage networks were extracted from DEM. Further, a comparative study of simulated drainage networks extracted from DEM using GIS-based Arc Hydro model is carried out and the drainage digitized from surveyed topographic maps for identifying infiltration zones in an urban watershed, upper Bagmati which covers the whole Kathmandu valley. It has been verified that the automatic drainage extracted technique from DEM is an efficient and cost-effective method in comparison to manual digitization. Hence, thus obtained drainage networks may be very useful for environmental studies, watershed management, and storm water and groundwater system analysis.