[S-TT39] Synthetic Aperture Radar and its application

[STT39-P05] Influence of typhoon events, region tectonics and surface deformation on the geomorphological evolution of Hongye landslide in southeastern Taiwan

*Suet Yee Au¹, Guan-Wei Lin², Rou-Fei Chen¹, Yi-Chung Chen¹, Chun-Long Wu³, Ya-Zhu Yu³ (1.Department of Materials and Mineral Resources Engineering, NTUT, 2.Department of Earth Sciences, NCKU, 3.Soil and Water Conservation Bureau, COA)

Keywords:Multi Temporal InSAR(MT-InSAR), Geomorphometry, Microtopography, Large-scale Landslide, High-precision Airborne LiDAR

Following climate change and the increasing number of extreme weather events around the world, Taiwan, which is situated in a subtropical monsoon climate region and active orogenic belt with fragile geological materials, frequently suffers from natural disasters such as typhoons and earthquakes. In September 2016, a landslide occurred on the western slope of Hongye Village in Taitung County, causing rock debris to fall and damage the roads and houses there. This study used high-precision airborne LiDAR to interpret tectonic features, compare lineament structures, and calculate landslide volume, combined with MT-InSAR provided surface deformation rate from 2015 to 2020 using ALOS-2 radar images. An analysis of the post-disaster landslide area using 0.5m high-resolution LiDAR reveals varying topographical features and classifies the main structural topography, including main scarp, secondary scarp cliff, side scarp, erosion scarp, gully and sliding block. We observed the decline of the Hongye landslide 8 months before Typhoon Moranti in September 2016, hence it is effective to used MT-InSAR to observe susceptibility trends in the Hongye landslide. In the aftermath of a disaster, the vertical surface deformation is mainly rising, which means accumulation is occurring. There are indications that residual colluvium deposits are gradually moving downstream. Finally, a nearly real geological model was created based on the previous execution of ground resistance, core hole, and attitude. The slope is further confirmed by attitude as a dip slope failure type. This study indicates that the combination of MT-InSAR and high-resolution airborne LiDAR can determine the topographic features of landslides and monitor surface activities, making it an important analysis tool for the topography of landslides. Moreover, both the attitude and the subsurface geological data are useful for understanding the failure mode of Hongye landslides.