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Estimation of runoff

Hamid Reza Rezaei Javid
Dept. of Surveying Engineering, Faculty of Civil Engineering
K. N. Tossi University of Technology
Tehran, Iran
Email: [email protected]

Saadi Mesgari
Assistant Professor of Geoinformatics, K. N. Tossi University of Technology
Email: [email protected]

Abstract
Estimation of runoff in the statisticless hydrometric river basins is one of the most important cases of applied hydrology. In area of runoff volume prediction there is one method which in my opinion, stand out as clearly superior to alternative methods for use on ungaged areas. It was developed by the U.S.Soil conservation service and is called the Direct Runoff Analysis Method. One of major procedure must be developed before this technique can be applied to a particular watershed. That step involves relating physical characteristics that influence runoff include size, shape, and topography, soils, and vegetation. At first drainage analysis was performed on a terrain model. The Arc Hydro tools were used to derive several data sets that collectively describe the drainage patterns of the catchments. Raster analysis was performed to generate data on flow direction, flow accumulation, stream definition, stream segmentation and watershed delineation. Hydrologic soil groups (A,B,C,D) and landuse map were determined in region and my case study. Then two landuse maps and the hydrologic soil groups were combined and the CN map of the region will be developed. The calculated runoff was compared with observed runoff and it was found that the SCS method is efficient for the estimation of runoff.