Flood Mitigation Alternatives for Selected Reachs of Awash River from Logiya to Dubti
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Date
2015-09
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Addis Ababa
Abstract
Nowadays, extraordinary floods are common in many parts of Ethiopia causing a lot of losses to human lives as well as damage to property. Problems related to flooding have been inseparable in past decades in awash basin. The objective of the study is to evaluate various alternatives and select best engineering measures on basis of the performance of hydraulic parameters. A river model, Hydrologic Engineering Center River Analysis System, combined with GIS analysis was used to simulate water levels for steady, gradually varied flow and mapping inundated flood extents. The modelling was performed for four different alternatives, considering various channel modifications with different dimensions and levee construction. Using the hydraulic parameters such as flood inundation area, flood level, flow velocity and stream power on the downstream and outside of the river bend were used as evaluation and decision criteria for each alternatives. The performance of the hydraulic parameters demonstrates significant flood risk & environmental impact in agricultural and residential areas adjacent the rivers in selected reach of Awash River for proposed measures. A multiple decision-making method was used to find optimal flood mitigation alternative based on 50 and 100 years peak flood discharges in a selected reach of Awash River in between logiya & dubti. The decision analysis method, technique for order of preference by similarity to ideal solution, was used to compare different flood hazard mitigation measures based on flood risk, and environmental impacts criteria. The output of the analysis confirmed that a levee construction at the right side of the river bank adjacent to the residential area, which was superior to the other three alternatives.
Key words
HEC-RAS; Decision analysis; flood mitigation; TOPSIS
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Keywords
HEC-RAS, Decision analysis, Flood mitigation, TOPSIS