Application of the ARMB-2D Model to Simulate Sediment Flushing of Empty Storage in a Reservoir

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Ching-Nuo Chen, Chih-Heng Tsai, Yu- Min Wang

Monday 29 june 2015

17:54 - 17:57h at Mississippi (level 1)

Themes: (T) Sediment management and morphodynamics, (ST) Sediment transport mechanisms and modelling, Poster pitches

Parallel session: Poster pitch: 3A. Sediment - Erosion

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The amount of sediment yield caused by soil erosion from the watershed is not only in connection with hydrological and physiographic characters of the watershed but also determine the speed of sedimentation in the storage area of the weir or reservoir. Due to specific topographical and geological conditions in Taiwan, extensive erosions, land slides, and muddy flows occur accompanied by large floods during the typhoon and heavy rainstorm period. The effective volume of the reservoir is diminishing due to the amount of sediment deposition from the upstream watershed, thereby affecting the function of the reservoir. The existing reservoirs in Taiwan are generally facing the same problem_the large amount sediment deposition in the reservoir. In order to solve the problem of siltation of reservoirs, the siltation of reservoirs is typically reduced by reservoir dredging during the dry season both to increase the effective storage capacity of the reservoir and to extend the life of the reservoir, thus achieving the reservoir capacity of sustainability management and utilization. The reservoir of Agoden in southern Taiwan is used as an illustrative example in this study. The sediment is easy to silt up during typhoon and heavy rainstorm seasons because of the specific geological and meteorological conditions in the watershed of the Agoden reservoir. In order to understand the sediment flushing efficiency of the empty storage operation to decrease the amount of sediment deposition, the sediment flushing efficiency of the empty storage was simulated by the Alluvial River-Movable Bed-Two Dimensional Model (ARMB-2D Model). Simulation cases include seven various return periods: 2-, 5-, 10-, 25-, 50-, 100-, and 200-year of 24-hour and 48-hour design rainfall events. The simulation results indicate that the minimum of sediment flushing efficiency of the empty storage in a 24-hour design rainfall is about 58.16% whereas the maximum is about 58.98%. The minimum of sediment flushing efficiency of the empty storage in a 48-hour design rainfall is about 58.62% while the maximum is about 60.19%. The averaged sediment flushing efficiencies of the empty storage are 58.50% and 59.39% for 24-hour and 48-hour design rainfalls, respectively.