Estimating of rainfall soil losses in Oltu Anzav Watershed

Erosion is a key factor for sustainability of land management. This study aimed to determine the spatial distribution of estimated total soil loss amount and erosion severity in the Oltu Anzav Watershed located in the East of Anatolia, Turkey. This study was conducted by using Geographical Information Systems (GIS) based on Revised Universal Soil Loss Equation (RUSLE) method. Topsoil samples (0-30 cm) were collected in 129 sites and analyzed for soil erosivity factor (K). Furthermore, the spatial distribution of potential estimated soil losses that may occur was mapped with the modeling using different scenarios in the future. Five different erosion risk groups have been determined as slight, moderate, severe, very severe and extreme, in the watershed area. As a result, the average surface soil loss was estimated as 24.44 ton ha-1year-1. Also, two different scenarios were created to estimate soil losses in the future in this study. According to the first scenario, if rehabilitation processes are implemented in the degraded forest area, soil loss was estimated as 7.33 tones ha-1year-1. In the second scenario, if any measures are not taken for soil erosion and flood control, soil loss was estimated as 58.63 ton ha-1year-1. Finally, sedimentation should be reduced in the watershed by erosion and flood control projects and applications. Key words: Erosion, erosion risk maps, Anzav basin, revised universal soil loss equation (RUSLE), geographical information systems (GIS).