Flood Risk Assessment in Ethiopia

Abstract

Flood is a natural disaster. However human activities in many circumstances change flood behavior. Activities in the catchment such as land clearing for agriculture may increase the magnitude of flood which increases the damage to the properties and life. Natural hazards have caused severe consequences to the natural, modified and human systems in the past. These consequences seem to increase with time due to both the higher intensity of the natural phenomena and the higher value of elements at risk. Among the water-related hazards, flood hazards have the most destructive impacts. The paper presents a new systemic paradigm for the assessment of flood hazard and flood risk in the riverine flood-prone areas. Special emphasis is given to the urban areas with mild terrain and complicated topography, in which 2-D fully dynamic flood modeling is proposed. Further, the EU flood directive is critically reviewed and examples of its implementation are presented. Some critical points in the flood directive implementation are also highlighted.Flood generating factors, i.e. slope, elevation, rainfall, drainage density, land use, and soil type were rated and combined to delineate flood hazard zones using a multi-criteria evaluation technique in a GIS environment. The  weight  of  each  flood  generating  factor  was  computed  by  pair  wise comparison for a final weighted overlay analysis of all factors to generate the flood hazard map. The flood hazard map indicates that 2103.34, 35406.63, 59271.09, 162827.96, and 1491.66 km² corresponds with very high, high, moderate, low, and very low flood hazard, respectively.