FLOOD HAZARD MAPPING AND RISK ASSESSMENT BY USING GIS AND REMOTE SENSING BASED MULTI-CRITERIA ANALYTICAL HIERARCHY PROCESS APPROACH IN UPPER AWASH VALLEY BASIN, CENTRAL ETHIOPIA

Abstract

The objective of this study was to assess flood causative factors, flood hazard, and risk spatial distribution in the Upper Awash Valley Sub-basin using a Geographic information system and remote sensing techniques based on multicriteria decision analysis of the analytical hierarchy process approach. Seven flood causative factors (elevation, slope, drainage density, distance from the river, rainfall, soil type, and land use) were prepared, prioritized, weighted, and overlaid. Accordingly, the resultant flood hazard in the Upper Awash Valley basin revealed, 4.4% (27260.33 ha), 26.58 % (164423.9 ha), and 11.56 % (71544.33 ha) were subjected to very high, high, and medium flooding hazard area respectively. The developed flood risk map showed that 1.69% (10434.61 ha), 17.16% (106129.5 ha), and 11.23% (69448.3 ha), of the study area were subjected to very high, high, and medium flooding risk areas, respectively. The created flood risk map was compared to actual floods using satellite images, Google Earth, and ground observations by gathering ground truth points in places that had actually experienced flooding. The developed risk map showed good agreement with the areas that had been damaged by previous flood occurrences, demonstrating that the method was successful. The result gained from this study facilitates the identification of flood risk-prone locations, helps governmental institutions, and non-governmental organizations for flood risk preparedness and response measures effectively. Finally, an identified flood hazard and risk area demand integrated flooding risk management measures like strengthening institutional framework, Terracing, Land use planning, emergency response plan, timely and effective early warning. Moreover, it is recommended that water release from the upper stream hydroelectric reservoirs of the Koka Dam and the Awash hydroelectric power be regularly checked and discharged before it causes the Awash River to overflow