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Typhoon Megi (2010) had brought intense rainfall and hit the northeastern part of Taiwan. It caused a widespread rock fall, debris slide, rock slide, and debris flows along highway Route 9. The multi-hazard susceptibility map based on logistic regression approach and rock mass rating system (RMR) was adopted to evaluate the landslide susceptibility in this study. Firstly, the multi-hazard susceptibility model categorized the hazard potential for different geological hazards into low, moderate, and high level. Secondly, the study performed a geomechanical classification system for rocks according to field investigation along the vulnerable road section. The result reveals that a semi-quantitative hazard matrix combining with the both evaluations can assess the geological hazard appropriately. In addition, the high-resolution DEM extracted from airborne LiDAR and multi-temporal remote sensing images had been analyzed to examine the morphological change and geological structure for the landslide location with a high susceptibility. Finally, the detailed landslide susceptibility with three levels on highway is proposed and verified.

In this study, we demonstrate the capability of combining remote sensing and GIS technique to identify and map out the possible landslide and debris flow hazards along the South Link Railway in Taiwan. Using high resolution aerial photography, terrain models, landslide inventories, the disaster prone areas of 3 types of mass movements were identified. In total, 48 slopes hold high landslide susceptibility; 35 torrents have high debris flow susceptibility; the rockfall from 11 sites would reach the railway line. The result shows consistencies with hazard records and could provide vital information for railway line improvement, hazard prevention and mitigation purposes.