河川堤岸風險評估分析－以高屏溪為例

Abstract

臺灣常因颱風、豪雨等天氣現象引致水患，尤其當發生堤防溢潰堤事件時更會使水災害加劇，而此淹水災害是造成臺灣地區人民生命財產損失主要天然災害之一，再加上近年來氣候異常與全球暖化所導致之極端水文事件，其對災害之加劇更是必須嚴正面對的問題，因此水災風險管理是必須投注研究之目標，而風險分析即為風險管理之首要工作。 國內近年建立之許多淹水潛勢圖、水災風險圖等圖資，皆在呈現可能淹水的情況與災害衝擊之風險，並未針對堤防護岸進行評估，因此本研究針對河川堤防護岸，以高屏溪流域為研究區域進行風險評估分析，包括了水理危害之危險度以及堤防護岸潛在狀況之脆弱度，並使用層級分析法(AHP)和分析網路程序法(ANP)分別給予脆弱度因子和危險度因子權重，最後計算出高屏溪流域內各堤岸所對應之河道斷面之風險度分數並繪製風險地圖。 本研究先以莫拉克颱風情境之風險評估做模式驗證，再以現況情境之風險評估做成果探討，其驗證結果雖顯示模式有過度預警的情況發生，但對於莫拉克颱風期間高屏溪流域溢潰堤事件之預測準確度可達0.7，而偵測率更高達0.85，因此整體而言，模式對於高風險區域之預警能力表現良好。本研究分別考量了堤防護岸之危險度與脆弱度，並經由風險分析與風險地圖繪製來辨別水理衝擊及堤防狀況所造成風險較高之區域，以期提供將堤防護岸條件納入考量之更完善的淹水災害潛勢資訊。

In Taiwan, flood disasters caused by typhoons and heavy rain are often exacerbated by dike-break and overbank. These flood disasters are among the main natural disasters that result in the loss of lives and property in Taiwan. In addition, climate change have led extreme hydrological events and then further aggravated the flood disasters. Therefore, we should pay more attention to flood disaster risk management as a research topic, and focus on the risk analyses first. The flood inundation maps and flood risk maps established recently in Taiwan only reveal the information of probable inundation areas and disaster risk without analyzing the dikes and revetments. The risk assessment in this study aims at dikes and revetments in Kao-Ping River, including analyzing hydrologic hazard and structure vulnerability. By using analytic hierarchy processs (AHP), analytic network processs (ANP) and semi-quantitaive risk matrix, the risk scores of each river section that corresponds to the dikes and revetments in Kao-Ping River is computed. The risk maps are drawn based on these risk scores. This study first validates the risk assessment in Typhoon Morakot, and then discusses the result of risk assessment in 2010 scenario. The validation result shows that the accuracy of the model can reach to 0.7 and the probability of detection can even reach to 0.85 during Typhoon Morakot. This study considers the hazard and vulnerability and distinguishes the high risk areas of the dikes and revetments through the risk analysis and the risk map, hoping to provide more complete potential inundation information.