Microzonation of flood risk using geographical information system (GIS) (Case study: urban watershed Sabzevar)

Flood risk zonation is necessary for controlling and prediction of the amplitude of flood damage. The purpose of this research flood risk zones in the watershed is overlooking Sabzevar. Specific parameters of this study include; high-class layer, hydrography network, sloop classes, permeability, soil texture, isothermal, isohyet, lithology, vegetation, land use, hydrological soil group,aspect and erosion. was then required to prepare watershed layers, each layer according to the weight of its importance in the occurrence of floods. After weight determination, layers were compared with each other in a two by two manner by means of Expert-Choice software and then the resulted matrix of these comparisons were imported in Idrisi Software and final coefficients for layers were calculated. Finally, by applying these coefficients through Raster Calculation menu in ArcGis software, the map of flood risk zonation in the basin were overlooking Sabzevar.The flood risk zonation map reveals that about 9/5% of study area is located in the class of very high flood risk, 23/9% is located in high flood risk class, 46/4% is located in medium flood risk class and 20/3% is in low flood risk class.