氣候變遷對於蘭陽溪流域防洪系統衝擊與調適策略之探討

Assessing The Impacts on Flood Protection System and Appropriate Adaptation Strategies under a Climate Change Scenario in Lanyang River Basin

曾忠裕(Chung-Yu Tseng)

指導教授 ： 朱子偉 ； 謝龍生

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00385

摘要

由於氣候變遷與全球暖化影響，極端事件發生頻率逐漸增加，根據臺灣1970至2006年颱風降雨分析顯示，近年來(2000至2006年)之極端事件發生次數已是過去30年(1970至1999年)之兩倍以上；分析近幾年的極端事件特性顯示不但降雨量增加，且其降雨型態已由過去長延時降雨轉變為短延時降雨之特性，亦即降雨更為集中且強度變大，導致河川產生更大之洪水，溢堤機率大增，勢必對台灣整體防洪系統造成衝擊。
本研究旨在探討在SRES(Special Report on Emissions Scenarios)中的A1B氣候預設情境下，未來氣候變遷對於蘭陽溪流量及下游易淹水地區之影響。研究中以A1B情境產生之未來日雨量資料經頻率分析及區域雨型設計後求得5、10、25、50、100與200年重現期之24小時時雨量，再將其輸入到半分布並聯型線性水庫降雨-逕流模式模擬未來各重現期之設計流量，同時亦以SOBEK模式進行流域淹水境況模擬，評估各重現期之淹水情形。此外，本研究亦探討若移轉極端事件莫拉克與梅姬颱風至蘭陽溪流域，模擬其可能產生之衝擊。研究最後另針對氣候變遷所造成之衝擊提出短、中及長期調適策略，並實際模擬各調適策略機制後探討其淹水改善情況，期望可提供相關單位做為未來減災規劃之參考。
研究結果發現，在預設之未來氣候變遷情境下，模擬蘭陽溪流域各重現期之設計流量皆有增加(1%至50%)；下游地區淹水境況模擬結果則顯示在100年與200年重現期之淹水深度已超過3公尺；另外，莫拉克颱風極端事件模擬結果則發現，在蘭陽大橋之模擬流量已超過公告之200年重現期流量，且下游地區淹水深度皆超過3公尺；最後，數種調適策略機制模擬顯示，淹水超過3公尺之範圍有縮小13%以上外，也同時改善了溢堤之情形。

關鍵字

氣候變遷 ； 莫拉克颱風 ； 極端事件 ； 半分布並聯型線性水庫降雨－逕流模式 ； Sobek Model ； 調適策略

並列摘要

The impacts of global warming and climate change possibly result in more frequent occurrences of extreme rainfall events. In Taiwan, the rainfall analysis from 1970 to 2006 years indicates that occurrences of extreme events in recent years (2000 to 2006) are twice higher than the ones in the past three decades (1970 to 1999). Moreover, the rainfall types of extreme events in recent years show that both the increasing rainfall amount and the shorter duration imply more concentrated and heavier rainfall. As a result, this changing trend will lead to more severe floods, which increase the probability of bank failure and create tremendous impacts on flood control system.
This study aims to assess the impacts of climate change on flooding-prone areas in Lanyang river basin under the A1B scenario of SRES (Special Report on Emissions Scenarios). The generated daily rainfalls of A1B scenario were utilized to obtain the 24-hour design rainfall of 5, 10, 25, 50, 100, and 200 year of return periods, respectively, by performing the frequency analysis. Next, the design rainfalls of various return periods were input to the Semi-distributed Parallel-type Linear Reservoir Runoff model to acquire the design discharges. In addition, the SOBEK model was further applied to simulate the inundation depths around the downstream areas of Lanyang river basin. Furthermore, this study employed the extreme event, typhoon Morakot, to Lanyang river basin for assessing possible impacts. At last, this study proposes and simulates several appropriate adaption strategies to assess the effects of flood mitigation.
The study results show that the design discharges of assigned return periods increase from 1% to 50% under the presumed A1B scenario. Additionally, the simulating inundation depths are over 3 meters in the downstream areas for design storms of 100 and 200 year of return periods. Moreover, the simulation of typhoon Morakot indicates that flooding depths over 3m are prevailing around downstream areas and the discharge under Lanyang Bridge is past the amount of 200 year return period reported by Water Resources Agency. Finally, the simulation of adaption strategies displays the improvements of embankment overflow. The areas of inundation depth over 3m are found to be decreased up to 13%. Overall, the results of this study could be used to evaluate the capability of flood control system and present appropriate improvements for further disaster mitigation in the future.

並列關鍵字

Climate change ； Typhoon Morakot ； Extreme events ； Semi-distributed Parallel-type linear reservoir rainfall-runoff model ； Sobek model ； Adaptation strategies

參考文獻

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