都市地區洪水減災調適策略評估與研究

Abstract

近年來台灣都會地區發展迅速，人口逐漸往都市集中，尤其大台北地區為台灣都市化程度最高處，人口相當密集，區域內建築物林立，使得地表逕流增加，滲透面積大幅下降，當颱風或暴雨事件發生時，都市洪災易造成人民生命財產損失嚴重。因此評估都市洪災風險就顯得相當重要，如此一來才可擬定更好的政策與策略，以降低災害所造成的損失。 一般來說，危險度（Hazard）與脆弱度（Vulnerability）為風險度（Risk）之核心概念，當其中一因子降低時，風險程度也將隨著降低，若能同時將兩者有效地降低，更能減少都市區域之風險。本研究主要擬定因應氣候變遷條件下之調適策略：（1）增加都市地區雨水貯留量、（2）減少位於淹水範圍內之社會脆弱度，探討經調適策略後之減災效果。 本研究以台北市中央區為研究區域，研究中以現況條件為基準，將政府間氣候變遷專門委員會（Intergovernmental Panel on Climate Change, IPCC）提出之A1B模擬之結果視為未來情況並比較，並考量調適的策略（本研究在此有兩種調適策略），最後以ArcGIS呈現調適策略後之四種重現期10年、25年、100年、200年淹水潛勢圖及風險變化。結果顯示：在淹水潛勢模擬方面，都市地區增加雨水貯留量後可有效降低氣候變遷造成的淹水面積1% ~ 3%；整體風險評估方面，經調適策略後使台北市中央區高風險以上的風險面積降低至3.08% ~ 8.31%，以增加都市地區雨水貯留量並同時降少位於淹水範圍內之社會脆弱度之調適策略研究結果較優於其他情境之調適效果。

The urban areas have been rapidly developed in Taiwan in recent years. They are expanding and their populations are increasing, especially in the metropolitan Taipei city, which result in surface runoff surcharged during typhoons or rainstorms due to high building cover ratio. When the surface runoff exceeds the capacity of drainage systems of the city, the inundation and property losses result. The urban flood risk assessment is a useful tool for the decisions and strategies making in flood damage mitigation. In general, hazard and vulnerability are two factors for the risk analysis. This works in the way that one of the factors was reduced, the degree of risk will be going down. With reduction to both factors at the same time in metropolitan area, the less risk of flood disaster will be taken. In this study, the adaptive strategies for climate change, including (1) increasing water storage in urban areas, (2) reducing social vulnerability in flooding areas are investigated. The Center Taipei City (CTC) under present conditions is chosen as the study area. The A1B scenario simulations proposed by IPCC are used to compare the flood risks between the present situation and future variation that the effects of climate change are considered. The ArcGIS is used to render flood potential information and the flood risk for the return period of 10, 25, 100 and 200-year flood. It reveals from the flood potential simulation, the water storage increasing to meet the regulation of the Taipei city government will effectively reduce the effects of climate change by the decreasing inundation areas in 1% to 3% of the city areas. Overall risk assessment, the adaptation strategies will reduce 3.08% to 8.31% of the high-risk areas in the CTC. The adaptation strategy consists of increasing the water storage in urban areas and reducing the social vulnerability of flooding area is the effective way for the flood risk reduction in urban area.