Assessing land degradation in the Upper Manyame sub-catchment area, Zimbabwe using the RUSLE prediction model

Catchment areas exposed to rapid urban development are threatened by soil erosion and sedimentation, impacting service accessibility. The study aimed to predict soil erosion risk and sediment yield between 2000 and 2023. This study employed the revised universal soil loss equation (RUSLE) model to predict soil erosion and the sediment delivery ratio (SDR) to estimate sediment yield rates. The results estimated an average annual soil loss of 1.98 t ha−1 yr−1 in 2000 and 1.53 t ha−1 yr−1 in 2023, with the highest soil loss rate of 156.8 t ha−1 yr−1 recorded in 2000 and 103.6 t ha−1 yr−1 in 2023. Upland areas in the southern parts of the Upper Manyame sub-catchment area exhibited high soil erosion risk and exported high rates of sediment. Corresponding sloping areas on the flanks of river channels and the hilly regions were exposed to high soil erosion risk. The sediment delivery ratio values for the Upper Manyame sub-catchment area were inversely proportional to sub-basin spatial coverage, showing a strong relationship with the catchment drainage network. The average annual sediment yield for both time steps narrowly varied, ranging from 1.38 t ha−1 yr−1 in 2000 to 1.04 t ha−1 yr−1 in 2023.