Investigation of the Soil Characteristics on Desertification Potential in Alluvial Fans Using AHP-FUZZY SAW Method (Case Study: Alluvial Fans Surrounding Halghe Dareh and Jaroo Mountains, Eshtehard)

Abstract

Desertification event by eliminating plant cover leads to the unfavorable effects such as erosion, land degradation, accelerated floods and also unfavorable environmental outputs. In the investigation of pedological criterion affecting on land degradation in alluvial fans Surrounding Halghe Dareh and Jaroo Mountains, Eshtehard, Karaj, first, maps of slope classes, land use, and geology were created, then a map of units was founded by overlaying and crossing these maps and grid layer created by extension of ET GeoWizards in ArcGIS 10.3 software. In this research three indices of erodibility, salinity and permeability of soil were considered, finally, each of them was shown in the shape of the classified map. In this study, soil sampling was carried out to create maps of salinity, 159 samples, and permeability, 174 samples. Then, weights of criteria and consistency ratio were calculated by AHP method. In this research, FUZZY SAW method was used to prioritize the options, in the manner that after defining the triangular fuzzy numbers in four and seven level scales, the preferred index was calculated. The results show that the preferred index obtained from AHP-FUZZY SAW technique alters from 0.254 to 0.889 and 0.236 to 0.903 for four and seven level scales, respectively. According to the four levels of linguistic variables, 74/18% (4245/77 ha) and 25/82% (1477/67 ha) of the area were classified into two classes of low and very high desertification potential, respectively. The results also showed that in the seven levels of linguistic variables, 74/18% (4245/77 ha), 9/78% (559/53 ha), and 16/04% (918/14 ha) of the area were classified into three classes of low, high, and very high desertification potential, respectively