Investigation of Pedological Criterion Affecting on Desertification in Alluvial Fans Using AHP-TOPSIS Technique (Case Study: South East of Roudeh-shoor Watershed)

Investigation of desertification trend requires an understanding of phenomena that create changes singly or action and reaction together in an area that these changes were led to the desertification and land degradation. In the investigation of pedological criterion affecting on land degradation in Alluvial Fans, first, the map of units was created by overlaying and crossing maps of slope classes, land use, geology and grid layer created by extension of ET Geo-Wizards in ArcGIS 10.3. In this research, three indices of erodibility, salinity and permeability of soil were considered and classified. Then, the weights of each criteria and consistency ratio were calculated by the AHP method. The TOPSIS method was used to prioritize the alternatives in this research. After calculating the weighted normalized values, Euclidean distances and the relative closeness to the ideal solution were calculated. The results show that the relative closeness to the ideal solution obtained from AHP-TOPSIS technique alters from 0.016 to 1.000. The alluvial fans in the research area were classified into three classes of I, II, and IV from the view point of pedological criterion affecting on desertification using AHP-TOPSIS technique. The obtained results showed that 74.18 % of the area is in the low desertification potential, and 3.37 % and 22.45 % are in the high and very high desertification potential, respectively.