Evaluation of soil erosion and sediment yield spatio-temporal pattern during 1990-2019

Land use/land cover (LULC) change is an important measure to monitor the land degradation. This study focused on the Sebeya watershed located in the western province of Rwanda to evaluate the soil erosion and sediment yield spatio-temporal pattern from 1990 to 2019 occurred due to LULC change. Multi-temporal LULC maps of 1990-2019 and RUSLE model were used to achieve the objectives. The sediment yield was computed as a product of sediment delivery ratio (SDR) and the gross soil erosion. From the period 1990-2019, each year forestland decreased by 2.6%/yr, whereas the grassland, cropland, and settlement increased by 23.6%/yr, 14.5%/yr, and 81.6%/yr respectively. As a result, the mean soil erosion for 1990, 2000, 2010, and 2019 was 14.7, 28.3, 34, and 34.7 t ha(-1 )yr(-1) whereas the total sediment yield was 3254.15, 5029.8, 6814.56, and 9074.04 t ( )yr(-1) respectively. Cropland was an exception to the other LULC classes because it has generated soil erosion in very high severity > 50 t ha(-1 )yr(-1), while this severity class showed an upward trend. The study demonstrated that LULC change has a significant impact on soil erosion and sediment yield and suggests proper land-use planning and encourages afforestation to arrest soil loss.