Abstract
Abstract. Extreme rainfall with long-term period plays a principal role in triggering deep-seated landslide around the mountainous area. A well-known typhoon Morakot, the most destructive event occurred in August 2009, battered southern Taiwan and caused severe casualties in Siaolin Village. To reduce the damage and to prevent loss of life resulting from the catastrophic landslide, this study adopted high-resolution topographic data which extracted from airborne LiDAR scanning to interpret both recent and ancient deep-seated landslides in northern, central, and southern Taiwan. Firstly, a relief visualization technique called sky-view factor was utilized to generate the quasi-3D map by overlapping slope gradient, and multiple direction hillshading maps, allowing one to interpret manually detailed landslide topography and assess the hazard potential. The study area of the on-going project covers an area of 17,000 km2. This study recognized main scarp and landslide body in polygon pattern by landslide micro-topography interpretation; it showed more than 700 deep-seated landslides were mapped and located on Central Range and Western foothills in Taiwan. The spatial distribution of deep-seated landslide relates highly to the regional strike of formation, daylight at the toe, river-bank erosion, and drainage density. Additionally, the detrimental geomorphic and topographic features are extracted to evaluate the landslide activity in the future. For a landslide zonation which characterized with sharp scarp and greater deformation rate, it usually may represent higher failure susceptibility. This work also uses the 3-D terrain model created by drone photography and geomorphometric analysis to validate the expert-based landslide susceptibility. Furthermore, the result of the study will contribute updating the national-wide environmental geologic map and provide competent authority to make decisions reducing the geohazard risk.
Highlights
In a subtropical and tropical area of western Pacific, the rainfall of typhoon is much higher, resulting in many sediment-related disasters
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-3/W4, 2018 GeoInformation For Disaster Management (Gi4DM), 18–21 March 2018, Istanbul, Turkey generated by airborne LiDAR scanning during 2010 and 2015
Based on results of bedrock landslide mapping (Fig. 5) most bedrock landslides are distributed along the strike of the bedrock in western Taiwan, and most landslides are within the Central Range; a high elevation northeastsouthwest oriented range of mountains
Summary
In a subtropical and tropical area of western Pacific, the rainfall of typhoon is much higher, resulting in many sediment-related disasters. The primary purpose of this project includes two aspects: establishing national-wide deep-stead landslide inventory and assess reactivation of old landslides. Both expert-based interpretation and on-site survey are the main analytical process for landslide mapping and susceptibility classification. A generation procedure of sky-view factor relief map will be first developed to replace the traditional 8-directions hill-shading on high-resolution DTMs. the feature of the deep-seated landslide is extracted to identify the pattern and boundary. Detailed expert criteria are discussed to assess the possible reactivation of the old landslides This visualization result can provide the fundamental data for updating the environmental geological map and assist deciding the proper site with high priority for establishing long-term monitoring system
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