Flash flood risk assessment using geospatial technology in Shewa Robit town, Ethiopia

Flash flood is an extreme flooding event which is quick, short-lived, hazardous phenomena having negative environmental and socio-economic impacts. Flood risk management is essential to reduce the effects of flood on human lives and livelihoods. The main goals of this research were flash flood risk analysis and risk quantification in terms of land use land cover using geo-spatial technology in Shewa Robit town. In the present study, elevation, slope, drainage density, distance from river, NDVI, land use land cover, topographic wetness index and curvature were used as parameters determining flash flood risk. To realize these research objectives, all these data were reclassified in to five classes and different weights for each of them was assigned using analytic hierarchy process. Weighted Sum Overlay (WSO) analyses of ARC GIS software was employed to produce flood vulnerability map. Then, the accuracy of generated flood risk map was validated using historical flood data. According to the result, about 3.08%, 14.62% and 20.66% of Shewa Robit town are at a very high, high and moderate flash flood risk, respectively. In addition to this, flood risk was also quantified in terms of land use land cover. The result indicates that the settlement land use is the most vulnerable with an estimated area of 12.01 ha, 99.57 ha and 174.16 ha in very high, high and moderate risk classes. The outcome of the study will be applicable in flood hazard management and mitigation strategies.