Modeling land use change impacts and identifying erosion hotspots using RUSLE in a northwestern Ethiopian highland watershed

Abstract

This study aimed to assess the impact of land use land cover (LULC) changes on soil loss (SL) and sediment yield (SY) using the Revised Universal Soil Loss Equation (RUSLE) model in the Angereb watershed. The 1991, 2001, 2011, and 2021 Landsat TM and OLI images were used for classification. Cover management (C) and conservation practice (P) factors of the RUSLE model were prepared for each LULC map. The other three RUSLE factors, such as slope length and steepness (LS), erosivity (R), and erodibility (K) factors, were prepared from digital elevation model (DEM), rainfall, and soil data, respectively. The sediment delivery ratio (SDR) and the SL maps were used to calculate the mean annual SY of the watershed. Results indicated that cultivated land expanded from 29.6% in 1991 to 42.6% in 2021 at the expense of forest and bush/shrubland. The change in LULC from 1991 to 2021 increased the mean annual SL and SY by 57% and 39%, respectively. The erosion rate increased from 107 t ha⁻¹ yr⁻¹to 134.3 t ha⁻¹ yr⁻¹ on cultivated land between 1991 and 2021. In the Angereb watershed, areas classified under very severe erosion (> 50 t ha⁻¹ yr⁻¹) cover 23.1% of the total area but contribute approximately 99.4% of the overall soil loss, predominantly occurring on steep slopes. These steeply sloped regions represent critical erosion risk zones and should be prioritized for targeted soil and water conservation interventions. The study’s findings offer valuable insights for evidence-based policymaking and the development of effective watershed management strategies.