野溪高土砂災害之模組化防砂壩管理

地震頻發與氣候變遷導致野溪土砂災害劇增，危及下游公共設施與居住安全。針對當時巨量土砂所興建之防砂壩，在時過境遷土砂量減緩後，卻又顯出對長期野溪生態與水流河床連續性的危害。不變的防砂壩結構難以應付劇變的溪床土砂環境，因此有效經營管理防砂壩是現今重要的課題。為改善既有防砂壩難以變動的缺點，本研究以靈活可調整的模組化防砂壩也稱為會呼吸的防砂壩來達到滿足溪流不同時期的輸砂、防災或生態需求。本研究以惠蓀林場蘭島溪的兩個開口型防砂壩作為研究基礎，案例一在已淤滿的梳子壩，降低中間兩支墩柱，觀察其土砂調整及河相演變，作為未來土砂管理的參考。案例二興建一座模組化鋼管壩，長期觀測其攔阻土砂及漂流木的功能，並詳實記錄土砂變化趨勢研擬壩體調整方式。兩案例都在強調土砂多變的野溪，必須常態性經營管理防砂壩，且最終仍須以回歸自然野溪為原則。

關鍵字

會呼吸的防砂壩；模組化鋼管壩；自然野溪；土砂災害

並列摘要

Frequent earthquakes and climate change have caused a dramatic increase in extreme sediment disasters in torrents, and these disasters commonly threaten downstream infrastructures and residents. With the passage of time and reduction in sediment yield, the numerous check dams that were built in the past to deal with the vast amounts of sediment then carried by several torrents have recently become threats to the long-term ecology and sediment transport continuity. The unchangeable check dam structure cannot easily cope with rapidly-changing sediment transport, therefore, the effective management of check dams is currently an important issue in Taiwan. In order to remedy the difficulty of modifying existing check dams, this study recommends that adjustable modular check dams, which are also known as breathing check dams, be used to meet the varying sediment transport, flood prevention, and ecological needs of torrents in different periods of time. This study employed two cases involving open-type check dams located on Landao Creek, Huisun Forest. In the first case, after reduction in the height of two center piers in the slit dam that had already silted up, the adjustment in sediment and evolution in fluvial morphology were observed to provide a reference for the future removal dam. In the second case, a modular steel dam was constructed and used for long-term observation of the blockage of sediment and driftwood by the dam, and the resulting detailed records concerning sediment variation were used to draft dam structure adjustment approaches. The results of both cases emphasized routine management of check dams is necessary on torrents with highly variable bed load, and that it is indeed necessary to let torrents return to their natural state.

並列關鍵字

Breathing check dam ； modular steel dam ； nature torrents ； sediment-related disasters

國際替代計量

野溪高土砂災害之模組化防砂壩管理

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