GIS-based mapping of flood hazard areas and soil erosion using analytic hierarchy process (AHP) and the universal soil loss equation (USLE) in the Awash River Basin, Ethiopia

Abstract

Floods are the second most significant hazard in Ethiopia, primarily due to the country’s diverse topography, including highland mountains and lowland plains. The Awash River Basin faces numerous environmental challenges, such as land degradation, topsoil erosion, high population density, water deterioration, wetland destruction, desertification, and salinity issues. Floods exacerbate these challenges, making effective flood hazard mapping vital for land use planning and mitigation strategies. This study aimed to create a GIS-based flood hazard map and estimate annual soil loss using the Universal Soil Loss Equation (USLE) while identifying the primary causes and impacts of flooding and soil erosion in the basin. Key parameters for the flood mapping included elevation, slope, drainage density, mean annual rainfall, proximity to rivers, land use, land cover change, and soil type. The results indicated that ~ 51.4% (5,855,130.12 ha) of the basin is highly susceptible to flooding, while 40.6% (4,625,378.51 ha) is moderately prone, and 7.6% (866,358.09 ha) is at low risk. The study identified drainage density, elevation, and slope as crucial factors influencing flood vulnerability. Additionally, the total estimated soil loss in the Awash River Basin was found to be 31,049,739 tons per year, with a mean annual loss of 28.6 tons per hectare. This research pioneers the combined study of flood hazards and soil erosion in the study area, where such an integrated analysis has not been previously conducted. It contributes to enhanced flood management and environmental planning while aligning with the Sustainable Development Goals (SDG 13) regarding climate change mitigation and adaptation.