Dam Breach Analysis and Emergency Action Plan Case Study of Mhtsab Azmati Dam
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Date
2019-04
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Addis Ababa University
Abstract
This study mainly describes the different dam failure modes which can affect the downstream societies and property in the world wide and was aimed to analyze the over topping and piping mode of dam failures for the Mhtsab Azmati embankment dam due to their highly occurrence from the others. The hydrological assessment, the dam breach dimensions, the downstream flood hydrographs, the development of the inundation map and the emergency action plan were among the specific tasks done in this paper. The meteorological data, physical features of the dam, DEM, land use and land cover and stream flow from other gauged river were the data collected for this study. The hydrologic model HEC – HMS version 4.2.1, the regression equations MacDonald and Langridge Monopolis (1984), Froehlich (1995), Froehlich (2008) and Von Thun and Gillette (1990), the hydraulic model HEC – RAS version 5.03 and the Arc GIS tools HEC – GeoHMS and HEC – GeoRAS were also the methods which used for the analysis. The probable maximum flood (PMF) with its peak run off 833.33 m3/sec from the catchment was found and used as input for the unsteady flow simulation in the HEC- RAS model. The dam breach model was analyzed for both overtopping and piping mode of failures using the four methods of dam breach regression equations for each cases. Depending on the maximum probable flood generated from the catchment and the reservoir capacity, the result obtained using MacDonald and Langridge Monopolis (1984) for the overtopping mode of failure case was selected to the downstream flood analysis with the results of side sloe (0.5H: 1V), bottom breach width 15m, breach development time 1.18hr and peak flood of 727.2 m3/sec. The downstream inundation map of the flooded were also for the identification of the more risked area. An integrated emergency action plan was also provided by this paper in order to safeguard the downstream population and conclusion and recommendation were also included in this study.
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Keywords
Dam breach modeling, DEM, ArcGIS, HEC – GeoRAS, PMP, PMF, HEC – HMS, HEC – RAS, Inundation map and EAP