Using a DEM for obtaining the drainage-network for watersheds

It is very important to forecast rainfall-runoff exactly in the development and management of water resources. But hydrologic characteristic factors, which affect the course of rainfall-runoff, have temporal and spatial variety, so the studies examining closely this relation are under lots of difficulties. The use of GIS (Geographic Information System) in rainfall-runoff analysis is very effective not only collecting, analyzing, and storing sides of data than existing methods, but transporting sides of analytic results. GIS can use to acquire hydrologic information, which effect hydrologic phenomena such as meteorological factors, soil type map, and land use map, drainage system of basin, and it can quantify geomorphic and meteorological characteristics different from existing data extracting methods which are monotonous and consuming time. Digital elevation models (DEMs) are readily available data sets that represent the elevation of the earth’s surface at discrete points in a regular, rectangular grid. They also can be used to derive a wealth of information about the morphology of a land surface .The algorithms included in most raster processing systems use neighborhood operations to calculate slope, aspect, and shaded relief and points of inflection. they also present non-neighbourhood problems such as determining direction of flow in the interior of large flat area. A major emphasis in geomorphology over the past six decades has been on the development of quantitative physiographic methods to describe the evolution and behaviour of surface- drainage networks. These parameters have been used in various studies of geomorphology and surface-water hydrology, such as flood characteristics, sediment yield, and evolution of basin morphology This paper presents an investigation and a method of using DEMs to determine the surface-drainage (runoff) network for a watershed. The characteristics of each part of the watershed are different. The results are provided by using the ArcGIS software.

Using a DEM for obtaining the drainage-network for watersheds Keywords:

DEM , watershed , drainage-network