Comparison of classic and fuzzy analytic hierarchy processes for mapping the flood hazard of Birjand plain

Flood is one of the most destructive natural hazards which impose vast costs in order to compensate its effects, especially in areas where there are manifestations of human development (such as cities). Urban development, particularly in the margins of rivers, has increased flood damages in recent decades. The aim of this study was to develop flood hazard maps of Birjand plain based on analyses of multi-criteria decision-making and geographic information system (GIS). This model was developed using six criteria including precipitation depth, basin slope, permeability, land use, proximity to river, and sub-basin shape. In this method, paired comparison of options was conducted by surveying the experts' opinions in this field using a questionnaire, and geometrical averaging was employed to calculate the weights of the criteria. According to the map prepared by means of Fuzzy Analytic Hierarchy Process (FAHP), 1.17 percent of the catchment area of Birjand is imposed to very probable hazard of flood and about 10.77 percent of the basin area is of high flood hazard. Moreover, in accordance with the Analytical Hierarchy Process )AHP( model, 3.29 percent of the basin is in the high hazard zone and 12.23 percent is located within the zone of high hazard. Comparison of results indicated that FAHP mapping approach is more compatible with the recorded data of recent floods.