Deep-Seated Gravitational Slope Deformation and Slow-Moving Landslides Revealed by Multi-Period LiDAR and UAS Data in the Slate Belt of the Backbone Range, Central Taiwan

In the mountain area, Deep seated gravitational slope deformation (DSGSD) was a phenomenon that causes rock mass deformation under long-term gravity. In the Slate Belt of the Backbone Range, Taiwan where mainly slate distributed, it is more susceptible to develop DSGSD. After Typhoon Morakot (2009), the high-resolution airborne LiDAR topographic data of the entire island of Taiwan completed by 2016, which will be regularly updated every five years. This high-resolution airborne lidar topographic data could be applied to visual interpretation with the potential landslide area, multi-period data with activity of slope deformation. In this study, we used existing high-resolution LiDAR topographic data and the latest computerized 3D environments to conduct and explore preliminary geological information at the regional scale and potential large-scale landslide distribution with detailed topographical characteristics. The area of slow-moving landslides could be found by comparing multi- period LiDAR topographic data and UAV images. Through field investigations and UAV application in Lusan area of central Taiwan, the features caused by regional tectonic effects or DSGSD could be clarified and discussed activity and possible mechanism of rock mass failure caused by these DSGSD. The results help to understand the deformation mechanism of the slate area in the Central Range of Taiwan. In the future, we could further explore the possible causes of why DSGSD transform into catastrophic landslides.