Dam breach analysis: a case of Gidabo dam, Southern Ethiopia
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ORIGINAL PAPER
Dam breach analysis: a case of Gidabo dam, Southern Ethiopia H. B. Desta1 · M. Z. Belayneh2 Received: 7 November 2019 / Revised: 20 October 2020 / Accepted: 31 October 2020 © Islamic Azad University (IAU) 2020
Abstract Gidabo dam provides flood control and irrigation water supply for sugarcane and rice cultivation. The dam has 25.8 m height and 335 m crest length with side ogee spillway to pass 10,000 years’ flood. There were different economic developments downstream of the dam including irrigation command area and irrigation structures. Since Nature is full of uncertainties, it is likely that Gidabo dam can be subjected to sudden breaches due to the probable maximum flood. Therefore, dam breach analysis and flood inundation map preparation should be conducted. The Hydrologic Engineering Center’s River Analysis System new version was used to analyze the dam breach for overtopping failure. River analysis system Mapper which is Geographic information system tool of Hydrologic Engineering Center’s River Analysis and Geographic information system were used to develop flood inundation map. Dam breach parameters were calculated within the Geographic information system model by using beach parameter calculator tab. A two-dimensional unsteady flow simulation of the dam breach was performed by using the inflow hydrograph as upstream boundary condition. From the rainfall data analysis, the probable maximum precipitation resulting probable maximum flood was found 277 mm results a peak inflow of 6387 m3/s. It was found that the breach bottom width was 143 m while the breach side slope (horizontal: vertical) was 1.4:1 and 2.7 h breach formation time. The peak breach outflow was found to be 15,848.85 m3/s which covers 2050 hectares with maximum depth of 12.14 m. Keywords Gidabo · Breach · Overtopping · Probable maximum flood
Introduction Dams are hydraulic structures used to store, control and divert water, impounding it behind the upstream side of dam in a reservoir for different purposes, like hydropower generation, water supply, irrigation, navigation and transportation, etc. Although dams have many advantages, the risk that may happen due to the failure still exists. Dams can have a risk to downstream communities and properties if not designed, operated and maintained properly (Hayimanot 2015). In India, the worst dam disaster occurred in Machhu II dam which was constructed to serve an irrigation
Editorial responsibility: Josef Trögl. * H. B. Desta [email protected] 1
Department of Hydraulic and Water Resources Engineering, Dilla University, Dilla, Ethiopia
Department of Hydraulic and Water Resources Engineering, Hawassa University, Hawassa, Ethiopia
2
scheme. This dam failed because of excess flood, inadequate capacity of spillway and overtopping in August 1, 1979, an dam Kaddam also failed due to overtopping which resulted in 137.2 m of breach width on the left bank in August 1958 (Zagonjolli 2007). The term dam breach analysis is usually related to the process of studying a dam failur
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