Hazard Mitigation of a Landslide-Prone Area through Monitoring, Modeling, and Susceptibility Mapping

Abstract

Indigenous tribes living in the mountainous areas account for about one-fifth of the extreme poor of the world, and this has made their lives more vulnerable to climate change impacts and natural hazards. After a series of earthquakes and very strong typhoons, the tilting and cracking of dwellings, localized slope failure, and severe subgrade settlements, together with damages of retaining structures and drainage ditches along a section of the Provincial Highway No. 7A on the west wing of the Central Mountain Range in central Taiwan, have raised concerns to the safety of a nearby Indigenous settlement, which is situated at an elevation of about EL. +1800 m. This study investigated and identified the possible causes for a large-scale landslide-prone area on the Central Mountain Range by employing multi-temporal satellite and aerial images, site investigation, field instrumentation, geophysics tests, and uncoupled hydromechanical slope stability analyses. The results were then applied to deduce a sliding susceptibility map and remedial plans to prevent or mitigate the sliding in the vicinity of an Indigenous settlement. The infiltration of rainwater, an upraised river-bed elevation, and the erosion of the river bank at the toe of the large-scale slope were found to be the main triggering factors in inducing sudden and localized failures. Meanwhile, the process of mass rock creep was deduced to have activated the process of large-scale deep-seated gravitational slope deformation (DSGSD) on the study slope; the DSGSD could eventually turn into a huge and catastrophic landslide. The findings of this study would be valuable for formulating detailed countermeasures to protect and maintain the stability and safety of the Indigenous settlement located at the crest of the slope.