The phenomenon of erosion has always been viewed as one of the most important factors wasting the earth resources. Considering the increasing trend of soil erosion in aquiferous basins, the employment of exact measures and techniques for the examination and evaluation of erosion and destruction processes for conserving soil and water resources seems necessary. The region under study, the aquiferous basin of Davarzan, is in Sabzehvar. For the exact assessment of erosion phenomenon in this basin and determining the degree to which each of factors affect this phenomenon, a model of fuzzy logic has been utilized to determine the scope of erosion danger. The mentioned model can be used to exactly analyse the role of natural and human factors by considering a range of probabilities instead of assigning an absolute number to weigh factors. For increasing the exactness degree in calculation and the processing speed of information and compiling the layers of information, the geographic information system has been used within the framework of Elvis software. Then by employing the rules and combination of fuzzy membership functions, application of fuzzy algebraic sum, fuzzy algebraic multiplication and fuzzy gamma with 0.2, 0.5 and 0.8 functions, they have been tested by focusing on regional conditions so that the most appropriate measure can be specified for determining the scope of erosion danger. The results show that operator 0.5 in the model of fuzzy gamma offers the best scope in Davarzan basin.

Keywords: Erosion, Determining Scope, the Model of Fuzzy Logic, Aquiferous Basin of Davarzan, Sabzehvar