氣候變異對於都市淹水影響之評估與應用研究

Abstract

隨著台灣社會經濟發展與全球氣候變異，都市地區因颱洪暴雨所造成之淹水課題也日趨重要，根據「政府間氣候變遷研究小組」在氣候變異度及極端氣候之研究中，可知與淹水災害相關因子主要為極端降雨及海水位上升；其中又以極端降雨對於易淹水地區影響最劇。 本研究考慮氣候變異條件下，極端降雨事件發生機率增加對於地區淹水之影響，並從水利署在易淹水地區治理計畫中，挑選常用之SOBEK淹水模式進行評估。首先針對模式演算理論部分進行評估，瞭解其運算方法、流程架構、格網建構與功能特點；另一方面選擇台北市玉成抽水站集水區為應用案例，考慮在不同降雨條件與不同土地利用情形下，下水道、人孔與地表水流間之交互作用關係，並進行模式之檢定驗證；研析氣候變異前後不同水文條件，對於下水道系統、區域排水及地表淹水之影響。 研究結果顯示，氣候變異前後不同重現期暴雨，對於玉成集水區淹水範圍及深度產生變化，因此極端降雨事件對玉成排水系統保護程度之改變，確實值得重視。

The study of inundation resulted from typhoons and storms in urbanized area is more and more important, especially accompanied by the climate change and rapid growth of socioeconomic development in Taiwan. According to the study of climate change and extreme weather (Intergovenmental Panel on Climate Change), we can see that the main factors of flooding disaster are the extreme rainfall and sea level rise. Among them, the extreme rainfall has much larger impact on the inundation-prone area. In this study we consider the increase of probability of the occurrence of extreme rainfall event under the climate change condition, and evaluate the impact on inundation situation. The commonly used model, SOBEK, in Water Resources Agency’s inundation-prone area projects is evaluated. First, we review the theoretic bases of the models to realize the numerical scheme, grid generation and other characteristics. Second, we select the watershed of Yu-Cheng Pump Station in Taipei as the application example, considering the interaction relationships among the overland flows, sewers, manholes and the pump station capacities under different precipitation conditions and different Manning’s n. Calibration and validation of the numerical model is also executed. Through analyzing the impacts on sewer system, regional drainage and inundation under the hydrological conditions before and after the climate change, we propose the relevant countermeasures. According to the research result, the rainstorms of different return periods before and after climate change result in different flooding scopes and water depths in Yu-Cheng Catchment area. Therefore, it is worthy to consider the change of protection level in Yu-Cheng drainage system due to the extreme rainfall events.