Assessing soil erosion and sedimentation in the Chehelgazi mountainous watershed, Iran, using GIS and RS

Soil erosion poses a severe threat to water quality and soil health in semi-arid regions. Assessing soil erosion and sedimentation at the watershed-scale is crucial for managing water resources and soil. In Iran, empirical models, e.g., the erosion potential method (EPM), modified Pacific Southwest Inter-Agency Committee (MPSIAC), and universal soil loss equation (USLE), have drawn more attention than other models, due to the availability of input data and lack of reliable hydrometric station, especially for a long time span. In the present article, we evaluated the soil erosion intensity and sediment yield in the Chehelgazi mountainous watershed (western Iran) utilizing the EPM, MPSIAC, and USLE, combined with the sediment delivery ratio (SDR) module, and then compared them with the observations. The required input data for EPM, MPSIAC, and USLE models all were created in ArcMap 10.8 and ENVI 5.5. The sediment yield amount and soil erosion zonation map were then obtained by the models mentioned and validated by the hydrometric data. According to the results, most portions of the watershed were subject to moderate erosion risk. Moreover, the annual average sediment yield of 196.86, 99.30, and 84.84 kt year⁻¹ assessed by EPM, MPSIAC, and USLE combined with SDR, respectively, suggested the superiority of USLE-SDR and MPSIAC. As compared with the observed amounts of 86.46 kt year ⁻¹, the efficiency of USLE-SDR was astonishing. Overall, we conclude that the USLE model coupled with the Boyce (1975) SDR formula is the best for estimating sediment yield at Chehelgazi mountainous watersheds, while MPSIAC is better suited for mapping soil erosion state.