Deep-Seated Landslide Mapping and Geomorphic Characteristic Using High Resolution DTM in Northern Taiwan

Torrential rainfall and local geologic structure play principal roles in triggering deep-seated landslide around mountainous area. Typhoon Morakot (2009), the most destructive event occurred in 2009, battered southern Taiwan and caused severe casualties in Siaolin Village. For the purpose of reducing the damage resulted from geological disaster, this study adopted high resolution topographic data which extracted from airborne LiDAR scanning to map the recent and ancient deep-seated landslides in northern Taiwan. In this study, a visualization technique of sky-view factor was performed to generate quasi-3D relief image map by overlapping slope gradient, topographic openness, and multiple direction hill-shading maps, allowing us to interpret precisely the feature of landslide zonation. The study area covers an area of 5502 km(2). The landslide micro-topography interpretation were presented with main scarp and landslide mass in polygon pattern, it shows more than 200 deep-seated landslides located on Hsuehshan Range, Tatun volcano group, and Western foothills in northern Taiwan. The spatial distribution of landslide relates highly to the regional strike of formation and local drainage pattern. Additionally, the detrimental geomorphic and geologic factors are extracted to evaluate the landslide evolution. For high scarp ratio slope, it usually represents the landform of ancient landslide characterized with apparent slope deformations. This work also explores the relationship between geomorphic evolutions of landslide and susceptibility. The paper describes expert mapping method combing with topography enhancement technique and provides competent authority to assess landslide magnitude and reduce disaster risk.