Flood Hazard Mapping and Propose Mitigation Measure: a case of Wera District, in Halaba Zone, Ethiopia
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Date
2024-02
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Abstract
For flood prone areas, identifying flood generating factors, mapping flood hazardous zones and propose flood eliminating methods can increase the knowledge, awareness and individual initiatives to prevent themselves and their properties from flood effects by using appropriate flood mitigation measures before and during flood events. Developing Flood Hazard Maps for flood prone area can be developed by integrating geo-spatial information on flood conditioning factors. Based on the AHP and GIS techniques, Flood Hazard Map for Wera District was develop by using Soil data, Lu/Lc data, Drainage Density, Slope, Rainfall and Topographic data of the Catchment. This study aims to map flood hazardous area and propose mitigation measures, for Wera Woreda in Bilate River sub-basin by using GIS, HEC-HMS, AHP, HEC-RAS and HEC – GeoRas software. Depending on the L-momentum Ratio diagram of the three distribution methods, Gumbel Distribution was used for this study to compute peak discharge. Thus, the final peak Discharges for 2,5,10, 25, 50 and 100 years was estimated 119.44, 189.18, 235.36, 293.70, 336.71 and 379.94m3/s respectively. HEC-Geo RAS Software was used to develop river geometry such as: the river centerline, river bank, flow path and cut cross-section for Bilate River. HEC-RAS, hydraulic analysis includes the computation of the water surface profiles.
Based on the degree to flooding, the importance of selected factors was ranked to five flood hazard category, namely very low, low, moderate, high and very high flooding. The weight coefficients were determined for each parameter by Analytical Hierarch Process (AHP) and overlay of ranked spatial information result the final flood hazard map of study areas. The flood hazard maps indicate that 60, 91, 93, 58, and 12.5km2 corresponds with very high, high, moderate, low and very low hazard areas respectively for Wera Woreda. For this thesis work, I was try to compare construction of levee along the channel and channel modification as alternatives for remedial measures to protect the flood from study area. From two alternatives, construction of levee along the river was the best alternative for study area.
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APH, Flood Hazard, GIS, HEC-HMS, HEC-RAS, HEC-Geo RAS, Mitigation Measure