台灣近岸環境觀測、分析與模擬研究-氣候變遷下海岸防禦的非工程治理: 海岸後退帶的試驗規畫研究(I)
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2014/08-2015/07
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氣候變遷下對於海岸最直接的影響就是全球海水面的上升和極端天氣(風暴、 颱風)事件發生的頻率增加。臺灣對於海岸防禦的策略及方法，從傳統的海堤、護 岸等人工結構物的建造到突堤、離岸堤等之佈設，再到最新的複合式工法，應用岬 灣理論進行人工養灘等，期望在颱風事件中能保護人民生命財產的安全，減少損 失。但在抵抗颱風巨浪和暴潮的侵襲時，工程結構物常傳出破堤或遭越波造成海水 倒灌、海堤塌陷等災害。再加上硬性結構物的建置，也常因為干擾自然海岸環境系 統，導致引發局部地區的海灘侵蝕問題。因此海岸防護策略在氣候變遷的情境下 的，已不能再固守傳統的硬性防禦工法，必須在海岸防禦工程作為上有所調適，或 是應用非工程的環境治理方式來減輕災害的損傷。以沙岸地區的海岸防禦為例，工 程調適作法是進行人工養灘及沙丘建造等柔性工法，藉以建立起海陸之間的自然屏 障。但人工養灘在國外的經驗常被質疑生命效期不如預期，在沒有其他配套措施 下，導致工程維護費用不斷增高累積，終至超出社會的負擔能力。本研究提出一種 兼顧防災及自然環境生態維護的非工程治理方式，建議劃設海岸後退帶或災害緩衝 帶，可以獨立操作，也可和柔性工法搭配。透過環境規劃與管理方式，限制易致災 區內的新建房舍和土地使用，以達到海岸減災的目的。期望從國外經驗的學習，建 立台灣海岸後退帶劃設的標準作業程序，調查西部沙岸之災害脆弱性，並擇取適當 侵蝕熱點區段進行後退帶試驗劃設，為這項海岸管理新思維，踏出實作的第一步。
The direct effects of the global climate change are the rising sea levels and the increasing frequency of extreme meteorological events, such as typhoons or storms. In response to coastal erosion, engineered structures, such as seawalls, groins, and detached breakwaters, are usually used in Taiwan to protect the shoreline and to prevent the loss of life and property in hazardous typhoon events. However, the protective measures are shown to be lacking in their adequacy in combating strong waves and storm surges. Even worse, the concrete structures have always had negative effects on beach preservation. It is now the key moment to begin transforming traditional protection techniques into an approach that involves "soft engineering" or an alternative environmental governance approach that involves no engineering at all. Soft engineering approaches for coastal defense may include beach nourishment and dune reconstruction. They benefit from the natural barrier function of beaches and dunes, thereby avoiding the concrete structures’ negative effects on the ecological and aesthetic values of the coast. However, the life spans of these soft structures are always shorter than expected. The maintenance fee may reach an extremely high amount that the entire society could not afford, if no other supplementary measures are taken. This project proposes a hazard mitigation approach that does not rely heavily on engineered structures; instead, the approach involves planning coastal setback zones or the hazard buffer zones that may function alone or in combination with soft structures. Restriction of land use and buildings in the hazard-prone areas will represent a huge step toward environmental sustainability and will also greatly reduce the loss of people’s lives and properties in the future. This study will learn from foreign experiences on setback zones and propose a standard procedure for planning setback zones. Coastal hazard vulnerability along the western sandy coast of Taiwan will be surveyed and a zoning experiment will be carried out at an erosion hotspot sector.
The direct effects of the global climate change are the rising sea levels and the increasing frequency of extreme meteorological events, such as typhoons or storms. In response to coastal erosion, engineered structures, such as seawalls, groins, and detached breakwaters, are usually used in Taiwan to protect the shoreline and to prevent the loss of life and property in hazardous typhoon events. However, the protective measures are shown to be lacking in their adequacy in combating strong waves and storm surges. Even worse, the concrete structures have always had negative effects on beach preservation. It is now the key moment to begin transforming traditional protection techniques into an approach that involves "soft engineering" or an alternative environmental governance approach that involves no engineering at all. Soft engineering approaches for coastal defense may include beach nourishment and dune reconstruction. They benefit from the natural barrier function of beaches and dunes, thereby avoiding the concrete structures’ negative effects on the ecological and aesthetic values of the coast. However, the life spans of these soft structures are always shorter than expected. The maintenance fee may reach an extremely high amount that the entire society could not afford, if no other supplementary measures are taken. This project proposes a hazard mitigation approach that does not rely heavily on engineered structures; instead, the approach involves planning coastal setback zones or the hazard buffer zones that may function alone or in combination with soft structures. Restriction of land use and buildings in the hazard-prone areas will represent a huge step toward environmental sustainability and will also greatly reduce the loss of people’s lives and properties in the future. This study will learn from foreign experiences on setback zones and propose a standard procedure for planning setback zones. Coastal hazard vulnerability along the western sandy coast of Taiwan will be surveyed and a zoning experiment will be carried out at an erosion hotspot sector.