A study on slope failure susceptibility along the mountain route in the catchment of Chenyulan Creek

Abstract

山區公路在颱風期間的安全性是公路管理的重要課題，本研究收集1996 賀伯颱風、2001桃芝颱風、2004 敏督利颱風、2008 辛樂克颱風、2009 莫拉克颱風的雨量資料，及颱風前後的遙測影像，加上野外調查道路邊坡崩塌之潛勢評估方法。考慮因子包括：累積降雨、降雨強度、坡度、岩體強度、濕度指數、弱面與坡面關係等。本研究嘗試將地質、地形與降雨因素量化以建立地形指標、地質指標和降雨指標。由邊坡崩塌資料可得到某降雨指標範圍下地形指標和地質指標的關係，此結果可由降雨事件的預測，進而預測道路邊坡的崩塌。

The safety of mountain routes during typhoons is an important issue of road management. This research collects data of rainfall and satellite images before and after typhoons for the years of 1996, 2001, 2004, 2008, and 2009. In addition, field investigation is performed to develop a method for the assessment of slope failure susceptibility. The landslide susceptibility under heavy rainfall along the route is assessed with the factors including accumulative rainfall, rainfall intensity, inclination of slopes, strength of rock mass, wetness index, and orientations of bedding relative to slope surfaces. The geology, topography, and rainfall conditions are quantified to establish their corresponding indices. With the satellite images to locate numerous historical landslides, the relationships between topographic index and geologic index can be obtained with respect to various rainfall indices. The landslide susceptibility can be predicted with the forecast of accumulative rainfall and maximum rainfall intensity for a certain heavy rainfall event.