Assessment of Soil Loss by Water Erosion at a Large Basin Scale: A Case Study of the Cheliff Basin, Algeria

Water erosion is the main driver of soil loss in semi-arid mountainous regions, particularly in Algeria. Identifying the spatial distribution of erosion is a crucial first step, providing decision-makers with essential information to develop effective mitigation strategies. The main objective of this study is to apply the Revised Universal Soil Loss Equation (RUSLE) to estimate soil loss and rank the sub-basins of the Wadi Cheliff Basin (43,750 km2). Different geographical and non-spatial data sets have been employed to develop different thematic layers of the RUSLE factors, such as rainfall erosivity factor (R), soil erodibility factor (K), topographic factor (LS), crop management factor (C), and support practice factor (P). The RUSLE empirical model indicated strong spatial variability of soil loss across the Wadi Cheliff Basin, with estimated values ranging from 0 to 50 t ha−1 yr−1 during October 2017–May 2018. Higher erosion rates (20–50 t ha−1 yr−1) were concentrated in the northern part of the basin near the Mediterranean coast, primarily due to high rainfall erosivity (800–977 MJ mm ha−1 h−1 yr−1) and steep slopes (LS up to 29.48). In contrast, the southern part of the basin exhibited lower soil loss (0–10 t ha−1 yr−1), associated with lower rainfall and gentler slopes. Areas affected by extreme erosion (>50 t ha−1 yr−1) were very limited, representing only 0.02% in October 2017 and 0.40% in May 2018. Maximum soil loss values (224.00 t ha−1 yr−1 in October 2017 and 204.10 t ha−1 yr−1 in May 2018) indicate that high-intensity erosion is limited to specific localized hotspots, rather than being broadly distributed across the basin. Information on soil erosion patterns at the sub-basin level can guide the planning of effective conservation practices. Such information is helpful for the implementation of erosion control practices and improving overall environmental management in the basin.