QUANTIFYING SOIL EROSION IN THE UPPER AND MIDDLE CHELIFF WATERSHED: AN ASSESSMENT AND MAPPING APPROACH USING THE WISCHMEIER MODEL

Abstract

The soil erosion phenomenon is becoming a critical environmental challenge that is significantly impacting ecosystems, agriculture, and water resources. This study assesses and maps the soil erosion in the Upper and Middle Cheliff watershed in the northern part of Algeria by using the Universal Soil Loss Equation (USLE), which is integrated with Geographic Information Systems (GIS). Semi-arid climates, steep slopes, and sparse vegetation primarily cause significant soil erosion in the study area, which spans over 10,930 km2. The methodology applied in this paper incorporates thematic mapping of erosional factors, including rainfall erosivity (R), soil erodibility (K), topographic features (LS), land cover management (C), and conservation practices (P). The results reveal several erosion levels across the watershed, ranging from negligible erosion in flat, vegetated areas to severe erosion in steep, barren regions. Annual soil loss rates were categorized into five classes, where the highest rates reached 20.33 t ha-1yr-1 in some areas. Such high rates of soil degradation indicate critical hotspots where land productivity and ecological stability are under serious threat. The study emphasizes the urgent need to carry out targeted interventions of conservation, such as reforestation to restore vegetation cover, contour farming to minimize runoff velocity on sloping lands, and the construction of gabions to stabilize stream banks and trap sediments. These practices, when integrated, can substantially mitigate the soil losses. The findings provide essential insights for sustainable land management and erosion control strategies adapted to the fragile conditions of Algeria’s semi-arid regions, where soils and water resources are increasingly under pressure from both climate change and anthropogenic activities.