颱風時期水庫操作風險分析之研究－以石門水庫為例

水庫壩體之安全，除影響本身之功能及經濟利益外，同時關係到下游地區人民生命財產之安全。因此，水庫之操作應使水庫之最高水位不致發生溢頂或危及結構物之安全爲首要。然實際防洪操作時，具多標的之水庫除考量下游地區是否因漲潮而加重洪水溢堤之危險性，亦十分關注未來之用水需求，所以開始進行洩洪之時間一般較規線建議者爲晚。本文以石門水庫為研究對象，針對颱風時期因操作延遲所將導致之溢流風險進行探討。在此利用一階可靠度分析法、均值一階二級動差法以及蒙地卡羅模擬法進行分析比較。結果顯示，一階可靠度分析法確實可改善蒙地卡羅模擬法耗時、精確度不足之缺點，且其於近似破壞點處做泰勒級數展開，是較均値一階二級動法符合實際情況的分析方法。本研究結果顯示石門水庫因操作延遲1至6小時所導致之溢流風險隨延遲時數的增加而提高，惟溢流風險皆不高，此可供水庫管理單位於颱風時期操作之參考。

關鍵字

洪水溢流；防洪操作；可靠度分析；蒙地卡羅模擬法

並列摘要

The safety of reservoir not only affects its operation functions and huge economic benefit but also affects life well being, and property of people living downstream. Therefore, reservoir operation should insure the safety of reservoir. In many cases, however, due to the pressure from water demand for different purposes and in consideration of the effect of combining water release from reservoir with tide flow which could increase the overflow risk of river banks, the time of water release in flood control operation for a multi-purposes reservoir is usually later than the operation rule suggested. In this study, we focus on the risk of overflow due to delayed flood control operation in the Shih-Men Reservoir during typhoon seasons. We contrasts the analysis results of the First Order Reliability Analysis Method (FORM), and the Mean-Value First Order Second Moment Method (MFOSM) with results of the Monte Carlo simulation method which is regarded as accurate probability of overflow. The results demonstrate that the use of FORM for risk analysis not only can save the prolonged simulation time in Monte Carlo method but also can prevent the inconsistency by MFOSM method. The simulation results show that the risk of overflow is increased as delayed water release in flood control operation, however, in general, the overflow risk is quite small. We believe the analysis results provide a useful guidance or reference for the flood control operation.

並列關鍵字

Flood overflow ； Flood control operation ； Reliability Analysis ； Monte Carlo simulation

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