結合EFDC與雙向隨機顆粒軌跡模型在颱風事件中辨認泥沙潛勢來源區域

Incorporating Backward-forward Stochastic Particle Tracking Model into the EFDC model for Probable Sedimentation Source identification in Typhoon event

劉文嘉(Wen-Jia Liu)

指導教授 ： 蔡宛珊

國立臺灣大學/工學院/土木工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202104126

摘要

近年來，水庫淤積已成為重要的環境問題。水庫流域的脆弱性和過度開發是造成水庫淤積的原因。颱風事件發生時，除了大量泥沙從上游輸送到庫區外，密度流可能會演變，這將在一段時間內迅速增加濁度程度。尤其是台灣北部重要水利工程之一的石門水庫，已面臨泥沙可能在未來幾十年填滿的危機。因此，為了將水庫容量維持在可操作的範圍內，石門水庫泥沙輸移模式將利用三維環境流體動力學代碼 (EFDC) 進行建模以量化 2016 年颱風 MEGI 期間的泥沙濃度。在這項研究中，遺傳算法（GA）與 EFDC 相結合，可以通過生物演化過程客觀地尋找最佳參數。因此，EFDC的校準和驗證是通過在參數優化算法的幫助下比較兩組獨立的基於事件的水動力和泥沙濃度數據來進行的。接下來，將後向隨機粒子跟踪模型（BF-SPTM）進一步納入 EFDC 水動力和原始泥沙輸移模塊，以檢查泥沙粒子潛在來源的可能性。模擬結果有望為流量調節提供更精確的釋放時間，以確保有效去除密度電流的渣。由於水庫可能存在沉積源，因此可以實施有效的土地利用變化和限制風險易發地區的過度開發，以減少進入水庫的沉積物產量。預計 BF-SPTM 與 EFDC 的結合可用於模擬颱風事件中的沉積物輸送，並提供適當的水庫管理替代方案。

關鍵字

環境流體動力學規範（EFDC） ； 懸浮泥沙濃度 ； 後向隨機粒子跟踪模型 ； 可能的沉積源

並列摘要

The reservoir siltation has been of critical environmental concerns in recent years. The vulnerability and the overdevelopment in the reservoir watershed are the causes of reservoir sedimentation. While typhoon events happen, in addition to the great amount of sediment volume transported from the upstream to the reservoir region, the density currents may evolve, which will rapidly increase turbidity levels for periods of time. In particular, the Shihmen Reservoir, one of the essential hydraulic engineering projects in northern Taiwan, has been exposed to the crisis that the sedimentation may fill up in the next few decades. Therefore, in order to maintain the reservoir capacity to an operational extent, modeling the sediment transport patterns in Shihmen Reservoir will utilize the three-dimensional Environmental Fluid Dynamics Code (EFDC) for quantifying sediment concentrations during the typhoon MEGI in 2016. In this study, Genetic algorithms (GA) coupled with EFDC can search out the optimal parameters objectively through a biological process. Therefore, calibration and validation of EFDC are performed by comparing two independent sets of event-based hydrodynamic and sediment concentration data with the assistance of the parameter optimization algorithm. Next, the Backward-forward Stochastic Particle Tracking Model (BF-SPTM) is further incorporated into the EFDC hydrodynamic and original sediment transport module to check the likelihood of the potential source of sediment particles. Results of simulations are expected to provide a more precise release timing for flow regulation to ensure effective slag removal for density currents. Additionally, with probable sedimentation sources available for a reservoir, effective land-use change and restrictions on overdevelopment of the risk-prone areas can be enforced to decrease the sediment yields into the reservoir. It is expected that this incorporation of BF-SPTM into EFDC can be applied to simulate sediment transport in typhoon events and to provide appropriate reservoir management alternatives.

並列關鍵字

Environmental Fluid Dynamics Code (EFDC) ； suspended sediment concentration ； Backward-forward Stochastic Particle Tracking Model ； Probable sedimentation source

參考文獻

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