Abstract
Fincha’a Dam was constructed in 1973 for the purpose of electricity generation, irrigation, fishery and truism with 22.2m height and 340m crest length. Fincha’a dam is rock fill dam with uncontrolled over flow spillway. There are different economic developments downstream of the Fincha’a dam including hydropower pant, irrigation project, residential house and sugar factory. These economic developments are affected either dam break by overtopping or piping mode of failure. The calculated breach parameters by Von Thun and Gillette Regression equation are selected as input data into the HEC-RAS model for dam break analysis. The general objective of the study is to analyze Dam break by using hydraulic models (Hydraulic Engineering Center’s River Analysis system). For this study the failure location is assumed to be at the center of the dam due to presence of high hydrostatic pressure and develop equally in both sides. From the result of Fincha’a dam break simulation the peak discharge formed by overtopping mode of failure is more devastating than the piping mode of failure. The effect of dam breach parameters on discharge is more pronounced than that of the water level. Dam break has greater impact on the downstream location where is closer to the dam in accordance with the hydrograph at downstream locations. The created Fincha’a river network was exported to HEC-RAS model for further dam break analysis by addition of different geometric data including dam information, calculated breach parameters, initial condition, upstream and downstream unsteady boundary condition. After full computation the model result were exported to integrated Arc-GIS and HEC- GeoRAS model for mapping flood inundation. Developed inundation map guides the dam owners and emergency management authority to give emergency action plan for the highly affected area by flooding and used for planning future economic development activities.
Highlights
Dams have been constructed for thousands of years around the world for different purposes: flood control, electricity generation, irrigation, water supply, recreation and etc (21)
The average breach width and breach development time calculated by Von Thun and Gillette (1990) are 95.9m and 0.58hr for both of overtopping and piping mode of failure
Since the breach parameters calculated by Von Thun and Gillette (1990) regression equation is more reasonable than the other regression equation it is selected for Fincha’a dam break analysis
Summary
Dams have been constructed for thousands of years around the world for different purposes: flood control, electricity generation, irrigation, water supply, recreation and etc (21). In India the worst dam disaster occurred in Machhu II dam was constructed to serve an irrigation scheme (10). This dam failed because of excess flood, inadequate capacity of spillway and due to overtopping of water over embankment dam in August 1, 1979. Kaddam Dam was failed due to overtopping of water above the crest by 46cm and due to this mode of failure 137.2m of breach width has been developed on the left bank in August 1958 (1). The world’s worst dam failure like Banqiao Dam and the Shimantan Dam occurred due to the overtopping in August 1975 and around 85,000 peoples were died by flooding in China (15). The breakage frequencies of earth dams are almost four times greater than concrete dams or masonries (17)
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