水庫排砂操作對下游河道長期變遷之影響

近年來受到極端氣候影響，台灣各地方水庫多有泥砂淤積嚴重之問題，颱洪時期上游集水區土石沖刷或崩塌現象所產生之泥砂，為造成水庫淤積嚴重及水庫庫容急遽減少之主要原因，為有效減緩水庫淤積並延長其壽命。本研究利用經濟部水利署所於石門水庫所規劃之大灣坪防淤隧道為模擬案例，利用颱洪期間，將大量高含砂濁水排放於水庫壩址下游之後池堰，雖水庫能有效清淤，但勢必對下游河床之沖淤情勢產生影響。因此本研究以擬似二維數值模式NETSTARS為演算工具，分析未來水庫排砂操作時，下游河道底床之長期沖淤情勢及河防安全。模式利用現場資料進行檢定驗證，率定出相對較佳參數後，再應用於長期案例之模擬。研究結果顯示，長期進行排砂操作若持續進行30年會使河床變化趨近於平衡，但會造成下游局部河段砂源增加。若未配合河道疏濬，將對部分河段之河防安全造成威脅，相關研究成果可供未來排砂操作之參考。

關鍵字

防淤隧道；數值模式；排砂操作

並列摘要

In recent years, the reservoir sedimentation problems were seriously happened in Taiwan due to extreme weather. In order to decrease sediment deposition in the reservoir, the sediment was released into downstream river during flood period using bypass tunnel. Sediment deposition and erosion would affect bed variation significantly in the downstream river reach. The quasi-two dimensional model, NETSTARS, was applied to investigate hydraulic characteristics and corresponding river sedimentation behavior in the Dahan river basin. The model was calibrated and verified with field survey data. The results showed that the cumulative amount of sediment in the long-term case was more than the general typhoon flood event. Sediment deposition situation was also more serious, therefore, the water elevation was rise up at peak discharge; it was threaten to flood-prevention work. The variation of bed elevation after 10, 20, 30 years, will reach nearly equilibrium 30 years later. Through field survey and numerical analysis results, we can develop coping strategies in order to achieve sustainable river management purposes. The study results about the function of sediment-prevent bypass tunnel could be offered in feature.

並列關鍵字

Bypass Tunnel ； Numerical Model ； Sediment Releasing

國際替代計量

水庫排砂操作對下游河道長期變遷之影響

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