Study of sensitivity of rock units to erosion by Sediment Yield Potential method in Sorhe drainage basin, N of Karaj

Erosion is one of the most active processes in surface of the earth. Erosion can cause soil destruction, shortage of groundwater, rangeland degradation, and eventually much damage to agriculture and livestock. Sorhe drainage basin, with an area of 39.4 square kilometers, is located in North Karaj. The study area is mostly formed by sedimentary and pyroclastic rocks. Kahar Formation with the Precambrian age is the most ancient rocks and Quaternary deposits are the youngest rock units in this area. Over 50 percent of the total area belongs to Karaj Formation rock units. Erodibility of rock units are affected by six main factors:geology, climate, tectonics, slope, vegetation cover, and weathering. The most important factors to erosion in this area belong to tectonics and slop. In addition to sedimentology and petrography of rock units, using experimental method of Sediment Yield Potential (SYP), the sensitivity of the formation was calculated in 5 classes. On this basis, Soltanieh formation is the most resistant with low erosion and Quaternary deposits of Qal and Qt are most sensitive rock units to erosion. Sediment yield rate was estimated 889.27 tons per hectare in the year.According to obtained information and using Arc GIS software, erosion type maps,susceptibility of formation to erosion, and finally sediment yield potential map (SYP) were prepared in Sorhe drainage basin.