都會區洪災耐受度分析

Abstract

近年來由於快速都市化及全球氣候變異導致重大洪災事件頻繁發生，使得都市地區每每受到洪災影響皆產生淹水災情及金額損失。本研究以新北市塔寮坑溪流域及臺中市旱溪流域作為研究對象，探討都市化過程中災害損失變化情形，並找尋調適策略以降低災害損失、提升都會區耐受度。本研究所使用的地表淹水模式中反映都市化之影響因子，加入調適策略設定進行模擬，並以2004年艾利颱風淹水事件驗證塔寮坑溪流域之模式，以2008年卡玫基颱風淹水事件驗證旱溪流域之模式，透過實測淹水資料範圍及淹水模擬結果比對，兩研究區域之模式模擬淹水趨勢皆大致符合實測淹水資料。 本研究根據研究文獻及臺灣現有法規，找出三種適用於臺灣地區之耐災工程性策略，分別為滯洪池、建築物貯留、移動式抽水機，藉由淹水模式建立模擬情境，各自比較三樣調適策略之調適效果。之後也根據土地利用情形建立都市化前(1997年)情境、現況(2007年)情境，及現況加調適策略情境和現況加擴大調適策略情境，並以25年及100年重現期距雨量進行模擬，將淹水模擬結果結合土地利用災損資料，分析討論都市化前後災害損失變化和調適策略之減災效能。研究結果顯示滯洪池為三樣調適策略中效果表現較佳之策略。在25年重現期降雨模擬下，現況加調適策略和現況加擴大調適策略兩情境，大致可將現況之災損降低至接近都市化前之災損程度；但在100年重現期距之大雨量影響下，調適策略效果明顯減少，顯示工程性調適策略之極限和不足。未來都會區應建議以非工程性調適策略提升都市耐受度，以因應在淹水事件發生時，能有效地降低災害損失及快速回復都市運作機能。

In recent years, urban areas suffer from flood disasters and flood damage losses due to the combined effects of rapid urbanization and large scale flooding events caused by global climate anomaly. This research selects Ta Liao Keng Drainage in New Taipei City and Han Drainage in Taichung City as the study cases, and discusses the changes in flood damage losses of urbanization, surveying appropriate adjustment strategies to reduce flood damage losses and enhance urban resilience. The present flood inundation model considers the urbanization factors and sets various adjustment strategies to conduct flood inundation simulations. The flood inundation model is confirmed with the flooding event of Typhoon Aere (Year 2004) in Ta Liao Keng Drainage and of Typhoon Kalmaegi (Year 2008) in Han Drainage. In comparison with the flood investigation data and the simulated results, the numerical predictions in the selected two study cases are matched to the real investigation data finely. This research surveys several related references and existing regulations in Taiwan about the strategies for engineering resilient adjustments, and selects three main adjustment strategies (i.e. detention pond, building retention, and transient pump) that are suitable for reducing the flood damage losses regarding urban areas in Taiwan. Through the modeling scenarios conducted in the flood inundation model, this research compares the efficiency of three adjustment strategies, and then establishes various modeling scenarios such as scenario 1: before urbanization (land use data of year 1997), scenario 2: current status (land use data of year 2007), scenario 3: current status with the total adjustment strategies, and scenario 4: current status with the ampliative total adjustment strategies. The modeling scenarios are simulated by repeating 25-year and 100-year return period rainfalls. Furthermore, the present research combines the flood simulated results and flood damage losses of different land use data to analyze the changes in flood damage losses between scenario 1 and scenarios 2 to 4 and discuss the mitigation efficiency of the selected adjustment strategies. Based on the simulated results, this research indicates that the detention pond presents the best mitigation efficiency among three adjustment strategies. In the simulated results of 25-year return period rainfall, the effects of the total adjustment strategies and the ampliative ones can reduce flood damage losses of scenario 2 to be close to that of scenario 1. However, in the simulated results of 100-year return period rainfall, the mitigation efficiency of the adjustment strategies declines obviously. This result demonstrates that engineering adjustment strategies have limitations and insufficiency on the extreme rainfall events. In the future, enhancing urban resilience for urban areas by the non-engineering adjustment strategies is suggested. When serious flood events happen, urban areas of concern can effectively reduce flood damage losses and recover urban function as usual soon.