Zoning of Gully Erosion in Catchment of Dyreh by Analytical Hierarchy Process (AHP)

Gully erosion can be considered as one of the advanced and critical forms of water erosion causing the destructors of the large amount of the earth. Identifying the factors that have an important impact in the occurrence of this type of erosion and its zoning can also be considered as one of the essential and important tools for managing and controlling this phenomenon. This study has been carried out with the purpose of identifying the factors affecting on the creation of gully erosion and the stimulation of the possibility of its occurrence in Dyreh catchment. The most effective factors in gully creation are: slope, slope direction, horizontal and vertical curvature of the slope, lithology, distance from waterway, and distance from the road. The land was selected and then these layers were created in GIS. Therefore, in the creation of gully erosion, they were classified based on preferences in order to have a paired comparison in the matrix table. Finally, the act of weighting the functions and overlapping of the layers were done by Arc GIS software and according to the resulting coefficient's hazard zonation map obtained in 6 layers: without risk, very low risk, low risk, medium risk, high risk, and too high risk. The final coefficient of numerical value was defined using the numbers obtained by multiplying the weight of each criterion in the index anywhere between zero and 100. In which the more tendency to 100 indicates as high risk of landslide’s, and the coefficients close to zero indicate that there is less risk and that its occurrence is without danger. The results further showed that %36 of Dyreh basin faces high risk, and too high risk causing the displacement of large volume of soil.