應用環境指標劃定阿里山溪集水區道路沿線崩塌潛勢之研究

2009 年莫拉克颱風侵襲台灣，累積雨量超過2500mm，造成中南部山區發生嚴重崩塌，其中嘉義阿里山地區累積雨量達3059.5mm，為莫拉克風災中降雨量最高的地區，使阿里山溪產生嚴重的崩塌情形，進而危害道路沿線與其他相關之保全對象；本研究旨在分析阿里山溪集水區內道路沿線之崩塌潛勢，利用SPOT 衛星影像進行影像相減萃取新增之崩塌地範圍，結合土地利用及地形資料，運用各類環境指標，探討不同崩塌類型與道路崩壞之相關性，並以不安定指數(DVM)進行崩塌潛勢因子權重劃分。結果顯示道路沿線之地形濕度指數為道路崩塌之重要指標，其權重為0.28；將各崩塌潛勢因子套疊後，以高潛勢區域之崩塌率為最高，與實際莫拉克崩塌災害案例相符，故模式可有效標出危險路段之區位，供相關單位監測管理之用。Typhoon Morakot lashed Taiwan in 2009. It brought more than 2,500mm accumulated rainfall and caused a lot of catastrophic landslides in central and southern Taiwan. The highest accumulated rainfall in the area of Alishan reached 3,059.5mm which is the highest in the island. The furious rainfall resulted in many massive landslides that affected the protected targets along the roads. The purpose of this study is to analyze the landslide potential along the roads in the watershed. Landslides extracted from SPOT images which coupled with environmental index calculated from land use and or topographic data was used to explore the correlation between landslide types and road failures. In addition, the Dangerous Value Method (DVM) is employed to derive the weight of factors to evaluate the vulnerability classes along the roads. The result shows that topographic wetting index with the weighting of 0.28 could be as an important factor to assess the landslide vulnerability along the roads. The highly potential areas are mostly located at the sites of highest landslide rate. It depicts that there is a good fit for the description of disaster sites caused by typhoon Morakot. Therefor the dangerous road sections could be efficiently identified as the hot spots for the use of further monitoring and maintenance