| Summary: | 碩士 === 國立交通大學 === 土木工程學系 === 99 === The reservoirs in Taiwan have many problems related to sedimentation, so the sediment flushing during flood season to maintain the reservoir capacity is an important topic of water resources. Among the flushing strategies, venting density current is the most suitable one for Shihmen Reservoir. This study extends the previous research of Hsu (2008), which considered one-dimensional explicit finite analytic numerical model with cohesive sediment in reservoir, and applied the numerical model to the Shihmen Reservoir. According to previous studies, the larger capacity of the low-level outlet is, the better reservoir sediment flushing efficiency will be. The mass of flushing sediment of each outlet could be obtained by integrating the sediment concentration along water depth at the dam determined by the method of van Rijn (1984) and the outflow of each outlet determined by water stage-outflow rating curve. Therefore, the sediment flushing efficiency could be calculated by dividing the mass of flushing sediment to the mass of the upstream inflow sediment.
By simulating the process of sediment flushing during Sinlaku typhoon in 2008 and Morakot typhoon in 2009, the flushing efficiencies of simulation results were compared by the observation data. And by simulating Aere typhoon in 2004, the flushing efficiencies of venting density current with different low-level outlet outflow capacities before and after the modification of the flushing facilities were also evaluated.
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