Quantifying Water Erosion in the Ziz Watershed (South-East of Morocco): A  Geomatics and RUSLE Approach

Abstract

Water erosion is a significant and irreversible natural hazard affecting large areas globally, with severe consequences for watershed soils. Geographic Information System (GIS) tools and Wischmeier's Revised Universal Soil Loss Equation (RUSLE) were employed to estimate soil losses in the Ziz watershed in southeastern Morocco. The RUSLE model considers five key factors: rainfall erosivity (R), topography (LS), soil erodibility (K), vegetation cover (C), and anti-erosion practices (P). By spatializing these factors, high-risk areas were identified and a comprehensive soil loss map for the watershed was created. According to the analysis, 93.16% of the watershed experiences soil losses classified as low, below 7 t/ha/year. Conversely, less than 1% of the area suffers significant soil losses, ranging from 20 to 58.0044 t/ha/year, exceeding the 7 t/ha/year threshold for water erosion. These high-risk areas are predominantly located in the northern upstream section of the basin, characterized by steep topography and substantial rainfall erosivity. Overall, the Ziz Basin exhibits relatively low erosion rates compared to similar watersheds in Morocco.