Spatial and temporal analysis of soil erosion and sediment yield in the shafe watershed, main ethiopian rift region: integrating RUSLE model, GIS, and remote sensing techniques

Soil erosion in Ethiopia, caused by poor land use planning, excessive cultivation, and excessive grazing, is an important environmental issue affecting the country's economy. This study was conducted in the Shafe watershed in the Gamo zone of south Ethiopia. The main objective of this research is a spatio-temporal assessment of soil erosion and sediment yield. The goal of the present study has been achieved by using the revised universal soil loss equation (RUSLE) model and the application of remote sensing and GIS techniques. The model input parameters include rainfall erosivity, soil erodibility, slope length and steepness, land cover and management, and support practice elements. The annual rates of soil erosion and the resulting sediment yield were calculated for the last three decades (2003, 2013, and 2023). The average erosion rates for the respective years (2003, 2013, and 2023) were 18.87, 19.79, and 10.78 t/ha/yr. The higher soil erosion rate was generally observed along stream channels, steeper topographies, and barren land. The mean soil erosion rate showed a slightly increasing trend between 2003 and 2013 but declined between 2013 and 2023, possibly due to the land use land cover (LULC) dynamics each year. Soil erosion per hectare per year was categorized into four severity levels: low (0–20 t/ha/yr), high (20–100 t/ha/yr), very severe (100–500 t/ha/yr), and extremely severe (> 500 t/ha/yr). The sediment delivery ratio value reveals that 21% of eroded soil materials are transported to a stream network, while 79% are trapped and redeposited within the watershed. Sediment yield values range from 30.92 to 38.51 t/ha/yr. It is found that from the total yearly soil erosion of 245,844.41 tons, 244,389.65 tons, and 140,348.86 tons of eroded soil in the years 2003, 2013, and 2023, over 11,334.30 tons, 11,455.29 tons, and 9,438.61 tons of sediment have been delivered to the mainstream channel and estimated at the watershed outlet, respectively. The study provides insight for local communities and concerned bodies to move quickly and put conservation measures in place in areas highly vulnerable to erosion. Afforestation, reforestation, soil conservation, stream bank stabilization, and terracing on steep fields are options available to address the worst locations that result in higher soil losses. This study contributes to the advancement of sustainable land use practices in Ethiopia, aligning with the SDGs of combating land degradation (SDG 15) and promoting sustainable agriculture (SDG 2). The findings provide insights into effective soil conservation strategies that can mitigate the adverse impacts of soil erosion and sediment yield on local ecosystems and communities.