Flood Hazard and Risk Assessment Using GIS and Remote Sensing in Lower Awash Sub-basin, Ethiopia

Awash River basin is a major river basin that has serious flood problems in Ethiopia. Given that flood hazard is spatial phenomenon, the application of GIS and Remote Sensing techniques are essential to the flood hazard/risk management process. Flood hazard and risk map are effective tools for reducing flood damage. The purpose of this study was to assess flood hazard and risk of Lower Awash sub-basin using GIS and Remote Sensing techniques. Flood causative factors such as slope, elevation, drainage density, soil type and land cover were developed in the GIS environment. The computed Eigen vector was used as a coefficient for the respective factor maps to be combined in weighted overlay in the Arc GIS environment. Flood risk assessment was done using the flood hazard layer and the two elements at risk, namely population and land use. The major finding of the flood hazard map of Lower Awash sub-basin indicated that 107,145.01ha (5%), 522,116.92ha(23%), 897388.95ha(39%) and 763045.31ha (33%) of the area considered in Lower Awash Sub-basin were subjected respectively to low, moderate, high and very high flood hazards. Thus, land use planners of Afar Region and Flood Management Units in the Awash Basin (Lower Awash Basin Area) could use those two maps to make environmentally sound land use decisions and manage the flood problems of the Lower Awash Sub-basin respectively. Keywords: Flood hazard; flood risk; geographic information system; remote sensing; Lower Awash Sub-basin