Unsteady-flow simulation of the dam break is performed using HEC-RAS and results are mapped using... more Unsteady-flow simulation of the dam break is performed using HEC-RAS and results are mapped using the RAS mapping. Inundation mapping of water surface profile, Velocity and depth results from dam failure models and provides a preliminary assessment of the flood hazard and provides insight for emergency preparedness. The Unsteady process is for gathering and preparing data, creating an unsteady-flow model in HEC-RAS, entry of dam breach parameters, performing a dam failure analysis, and mapping of the flood progression. Break parameters prediction, the understanding of dam break mechanics, peak outflow prediction were shown as the essential for the dam break analysis and flood mapping. The results show that dam break is a complicated and comprehensive process involving lots of principles. Koga Dam break due to overtopping elongates the time period of high water surface level, which increases the duration of risk. The design Probable Maximum Flood (PMF) is 570 m 3 /sec statically estimated and PMF also estimated in HEC-HMS model after calibration and validation is 537m 3 /sec. The calibration result of HEC-HMS model is the Nash-Sutcliffe Efficiency criteria for the calibration N=0.543 coefficient of determination (r 2 ) of 0.7334 daily based. Validation result is the Nash-Sutcliffe Efficiency N=0.6 and coefficient of determination (r 2 )=0.8.The result of the simulation under overtopping failure showed that the inundated area surrounding Koga River downstream of the dam is about 10.2 km 2 with maximum flood depth is 16 m, water surface velocity ranges from 0.00 to 11 m/s. Most of floodplain areas varied from middle to high flood hazard level, and only few areas had very high level of flood hazard especially on river side. Whereas under piping failure inundated area is 9.1 km 2 with maximum flood depth is 13 m, water surface velocity ranges from 0.00 to 6 m/s. This flood affect the downstream town Wetit Abay town settlement near Koga river and irrigation canal also affected. Dam break has a greater impact on the downstream location where is closer to the dam is high flood depth in accordance with the comparison of the hydrographs at different downstream locations. The structural flood control measurement to be recommended is to construct flood dike and flood gate. The non-structural measurement one is to improve watershed management and socialization of flood awareness.
Unsteady-flow simulation of the dam break is performed using HEC-RAS and results are mapped using... more Unsteady-flow simulation of the dam break is performed using HEC-RAS and results are mapped using the RAS mapping. Inundation mapping of water surface profile, Velocity and depth results from dam failure models and provides a preliminary assessment of the flood hazard and provides insight for emergency preparedness. The Unsteady process is for gathering and preparing data, creating an unsteady-flow model in HEC-RAS, entry of dam breach parameters, performing a dam failure analysis, and mapping of the flood progression. Break parameters prediction, the understanding of dam break mechanics, peak outflow prediction were shown as the essential for the dam break analysis and flood mapping. The results show that dam break is a complicated and comprehensive process involving lots of principles. Koga Dam break due to overtopping elongates the time period of high water surface level, which increases the duration of risk. The design Probable Maximum Flood (PMF) is 570 m 3 /sec statically estimated and PMF also estimated in HEC-HMS model after calibration and validation is 537m 3 /sec. The calibration result of HEC-HMS model is the Nash-Sutcliffe Efficiency criteria for the calibration N=0.543 coefficient of determination (r 2 ) of 0.7334 daily based. Validation result is the Nash-Sutcliffe Efficiency N=0.6 and coefficient of determination (r 2 )=0.8.The result of the simulation under overtopping failure showed that the inundated area surrounding Koga River downstream of the dam is about 10.2 km 2 with maximum flood depth is 16 m, water surface velocity ranges from 0.00 to 11 m/s. Most of floodplain areas varied from middle to high flood hazard level, and only few areas had very high level of flood hazard especially on river side. Whereas under piping failure inundated area is 9.1 km 2 with maximum flood depth is 13 m, water surface velocity ranges from 0.00 to 6 m/s. This flood affect the downstream town Wetit Abay town settlement near Koga river and irrigation canal also affected. Dam break has a greater impact on the downstream location where is closer to the dam is high flood depth in accordance with the comparison of the hydrographs at different downstream locations. The structural flood control measurement to be recommended is to construct flood dike and flood gate. The non-structural measurement one is to improve watershed management and socialization of flood awareness.
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