Dam Break Analysis and Risk Assessment [A Case Study of Tendaho Dam]

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Addis Ababa


This thesis analyzes the probable failure of a dam under a set of pre-defined scenarios, within the framework of a case study, the case subject being the Tendaho dam located at Afar Region of Ethiopia. The failure of the dam is not analyzed neither structural nor hydraulic wise but, is assumed to be triggered when certain critical WSELs are exceeded. Hence, the analyses focused on the aftermath of the failure and strive to anticipate the level of inundation at downstream of the dam itself. Break parameters prediction, peak outflow prediction were shown as the essential for the dam break analysis and eventually determined the loss of the life. Tendaho dam break was further modeled and analyzed using USACE Hydrologic Engineering Center’s River Analysis System (HEC-RAS Version 4.1) model based on available technical and geometric data. Water surface elevations and discharges occurring at downstream of the Tendaho dam were predicted spatially and temporally under the defined set of eleven scenarios. Eight of the scenarios were analyzed for overtopping failure of the dam. Two of the scenarios were analyzed for piping failure and the last scenario was analyzed to investigate the sensitivity of Manning roughness. Overtopping failure yielded more severe flow conditions at downstream. The worst case scenario was found to be scenario W4 (when all the three spillway gates are completely closed). Hence, indicative inundation map and settlements under risk were identified. Total numbers of fatalities for precise and vague understanding of warnings were found 1,012 and 2,972 respectively. The thesis study further addressed some available pre-event measures that may be taken in advance. Keywords: Tendaho Dam, HEC-RAS, HEC-GeoRAS, Breach, Dam Failure, Dam Break Analysis



Tendaho Dam, HEC-RAS, HEC-GeoRAS, Breach, Dam Failure, Dam Break Analysis