Determining the Appropriate Areas for Flood Spreading Using Decision Making and Geographic Information System in Farimaneh Watershed, Joghatay County

In arid and semi-arid regions where there is low rainfall with inappropriate distribution, one of the ways to use floods is to spread them in susceptible areas. The aim of this study is to find the best place for flood spreading using GIS and decision-making methods in Farimaneh watershed. For this purpose, the slope, topography (altitude levels), geology, land use type, soil permeability, geomorphology, geological formations, vegetation, and soil factors were used. For weighting the quantitative variables, fuzzy logic with trapezoidal and triangular membership function, and for qualitative variables, fuzzy logic with hierarchical analysis was used. Flood spreading prone areas were presented using GIS and the concepts of layer integration from fuzzy logic, Boolean logic, and overlay index methods. To determine and prioritize susceptible areas the Boolean operators AND OR, fuzzy AND OR, Fuzzy algebraic and sum-product, fuzzy gamma from 0.1 to 0.9, and multi-criteria evaluation was used. By comparing the obtained results with the observational data, it was concluded that the Fuzzy and, multi-criteria evaluation and fuzzy gamma 0.8 and 0.9 methods were most consistent with the observational data and among these methods, the multivariate evaluation method was found to be more appropriate. Also, among the parameters, slope, vegetation cover, and permeability had the highest weights.