Mapping Potential Soil Loss and Erosion Hotspots for Targeted Conservation in a Mountain Basin: A RUSLE–GIS Approach

Abstract

Soil erosion is one of the most critical forms of land degradation affecting Mediterranean environments, particularly in mountainous regions where steep slopes, intense rainfall, sparse vegetation cover, and fragile lithological formations accelerate soil loss processes. This study aims to assess the spatial distribution of soil erosion risk in the upstream part of the Bin El Ouidane Dam (Oued El Abid river basin, Central High Atlas, Morocco) using the Revised Universal Soil Loss Equation (RUSLE) integrated with Geographic Information Systems (GIS) and remote sensing techniques. The RUSLE model was applied by combining rainfall erosivity (R), soil erodibility (K), topographic (LS), land cover (C), and conservation practice (P) factors derived from climatic, topographic, geological, and satellite data. The results indicate moderate spatial variability in rainfall erosivity, with station-based R-factor values ranging from 52 to 102, while the interpolated values within the watershed range from approximately 63 to 87. Soil erodibility is dominated by the moderate class (0.20 < K ≤ 0.28), which covers 71.258% of the valid K-factor raster area. The LS-factor analysis reveals that 81% of the basin is characterized by low topographic influence on erosion, whereas steep slopes are concentrated in limited mountainous sectors. Land-use analysis shows that bare land and agricultural areas occupy approximately 79% of the watershed, while 77.60% of the area lacks effective soil conservation practices. The final soil-loss map indicates that very low, low, moderate, high, and very high erosion classes account for 10.61%, 76.69%, 7.26%, 3.68%, and 1.76% of the valid RUSLE output area, respectively. Although severe erosion affects a relatively small proportion of the watershed, these areas constitute critical hotspots for sediment production and reservoir siltation. These findings provide a practical basis for targeting soil conservation measures in the identified high and very high erosion zones, particularly through vegetation restoration, improved agricultural practices, and slope protection, thereby potentially reducing hillslope soil loss and subsequent sediment transfer toward the reservoir and supporting the long-term preservation of Bin El Ouidane Dam’s storage capacity.