| 摘要: | 西元1845年雲林口湖發生嚴重之風暴潮事件，造成萬人喪生，為台灣歷史上最嚴重之風暴潮事件。為重建1845口湖風暴潮事件，本文發展風暴潮影響強度分析法（SSIIA）。該法以現行於中央氣象局之COMCOT-SS 風暴潮模式為基礎，進行大量單元颱風之風暴潮模擬，以建立颱風位置對風暴潮與溢淹高程之SSIIA敏感關係圖。本研究為重建颱風路徑，發展颱風路徑對風暴潮影響分析法。該法透過SSIIA之分析結果進行分析，以求得可能之颱風路徑組合，再考慮颱風移動速度之差異性，得出最嚴重影響行進速度之路徑，最後由該結果建立1845年事件之可能情境路徑。並以COMCOT-SS風暴潮模式，模擬該情境路徑所生成之風暴潮。最終將所模擬之結果與歷史文獻記載比對，以獲得結論。
研究結果顯示，根據SSIIA圖各單元颱風源對雲林縣口湖鄉之高影響位置皆位於口湖或口湖北部一帶。而位於北緯22.7度以南之地區，由於其對於口湖造成持續之離岸風影響，導致該區域單元颱風之影響較低；根據颱風路徑對風暴潮影響分析可知，SSIIA法分析範圍以外之颱風路徑，其颱風路徑對風暴潮敏感性大幅降低至可忽略之程度；而於颱風行進速度對於口湖鄉之影響分析可知不同之行進速度其對於口湖之風暴潮影響有類似之影響。
於1845雲林口湖風暴潮事件歷史紀錄中，其記載該颱風事件颱風有影響之地區涵蓋小呂宋國，因此本研究以颱風情境路徑通過巴士海峽之路徑為最終重建路徑，其颱風於巴士海峽生成，並向臺灣海峽中線移動，並沿口湖與澎湖之間穿越並沿海岸線西側北上至東海南方。
根據COMCOT-SS風暴潮模式模擬結果可知於1845雲林口湖風暴潮事件中，颱風中心於第24至30小時雖並未登陸台灣，但其會對於口湖鄉引進之強烈西風，導致嘉義縣及雲林縣一帶低漥地區嚴重之風暴潮溢淹，並於口湖一帶造成約3.7m之最大風暴潮潮高，及約2.6m之最大溢淹高程，此模擬結果與口湖鄉之歷史記載影響範圍相符合。
本研究所建立之分析方法，可系統性分析沿海低窪地區之風暴潮溢淹潛在災情，有助於進行風暴潮風險評估及災防規劃。
;In 1845, a severe storm surge occurred at Yunlin Kouhu, killing thousands of people, making it the most powerful storm surge event in Taiwan’s history. This research develops the storm surge impact intensity analysis method (SSIIA) to reconstruct the 1845 Kouhu storm surge. This method is based on the currently operating COMCOT-SS storm surge forecast model in the Central Weather Bureau. It conducts many simulations to establish the SSIIA sensitivity map of typhoon location to storm surge and inundation.
In addition, this research is to reconstruct the typhoon track and develop an analysis method for the influence of the typhoon track on the storm surge. First, the technique analyzes the results of the SSIIA to obtain possible combinations of the typhoon track. It then considers the variation in typhoon movement speeds to get the route that affects the study area most severely. The research finally establishes the scenario of the 1845 event from the results. Then, it uses the COMCOT-SS storm surge model to simulate the storm surge generated by the method and compare the simulated results with historical documents to conclude.
According to the SSIIA map, the study results show that the high-impact typhoon sources in the study area in Yunlin are all located in Kouhu or the northern part of Kouhu. However, in the area south of 22.7 ?N, due to its continuous offshore wind impact on Kouhu, typhoons′ effects in this area are relatively low. Furthermore, compared to the worst-case, influences from the racks outside the SSIIA region are negligible, and various typhoon forwarding speeds have similar results to the flooding zone in Kouhu.
The historical record of the 1845 Yunlin Kouhu storm surge event records that the area affected by the typhoon event covers “Little Luzon”. Therefore, this study takes the track that goes through the Bashi Strait as the reconstructed scenario. Thus, the typhoon is generated in Bashi Strait and forwarded to the Taiwan Strait, and moving north to the southern East China Sea along the coastline of Kouhu.
According to the simulation results of the COMCOT-SS storm surge model, it can be known that during the 1845 Yunlin Kouhu storm surge event, although the typhoon center did not make landfall in Taiwan, the solid westerly wind would cause severe flooding in the low-lying area of Yunlin and Chiayi. The maximum storm surge height is about 3.7 m and a maximum flooding elevation of about 2.6 m in the Kouhu area. This simulation result is consistent with the historical record of Kouhu, and the scope of influence is consistent.
The analysis method established by this research can systematically analyze the potential disasters of storm surge flooding in low-lying coastal areas, which is helpful for storm surge risk assessment and disaster prevention planning. |
