Investigation of susceptibility of rock units to erosion, using EPM model in Abhar-roud basin

Erosion is a natural process which is developing all around of the earth and it is important in changing surface of the earth. The purpose of this research is preparation of maps of sensitivity of rock to erosion, erosion intensity, rate of erosion and sediment yield of rock units in Abhar-rood watershed by using an experimental model of EPM in a GIS environment. Abhar-rood watershed basin with 189256.1 hectares is located in the southeast of the Zanjan. The study area shows a semiarid and Mediterranean climate with average annual rainfall of 344/5 mm. There are geological formations related to Paleozoic, Mesozoic and Cenozoic in this region. Kahar Formation (Pre-Cambrian) is the oldest and Quaternary alluvial deposits is the youngest deposits. The region is mainly consisted of sedimentary rocks. For better study of the area, it is divided into eleven subbasins. In this research, the factors affecting erosion and its forms and also rate of erosion was calculated and then erosion types map is prepared. Map of sediment yield ratio was prepared using Arc GIS software and intensity of sediment yield was calculated by experimental model of EPM in each subbasin. Subbasin A7 shows the minimum and subbasin A2 the maximum annual sediment yield in this basin. The specific sediment yield was estimated 8.81 in tons per hectare per year in this area. Calculation of EPM model shows that the erosion intensity is very sever in Abhar-rood basin. The A2 subbasin should be the first priority for soil conservation programs.