Topographical and Geological Controls on Shallow Landslide Movement Types Identified by Satellite Imagery
YAMAGUCHI, Akari 1*, SATO, Go1, Tran The Viet 2, Nguyen Van Thang 2

1 First Author^s Affiliation: Department of Environment, Tokyo City University, Japan
2 Second Author^s Affiliation: Department of Civil Engineering, Thuyloi University, Vietnam

Abstract

In recent years, the frequency and magnitude of sediment disasters have increased due to heavy rainfall associated with climate change. In the southwestern region of Da Nang City, central Vietnam, a significant number of shallow landslides (hereinafter referred to as landslides) were triggered by the heavy rainfall associated with Typhoon Molave in October 2020. This study aims to clarify the relationship between topographical and geological conditions and the movement types of shallow landslides. Landslides were classified into four types: Slide-flow (Unchanneled), Slide-flow (Channeled), Slide-flow (Flood), and Slide/fall (Un-flow) based on satellite image interpretation. To characterize the topography for each movement type of landslide, topographic analysis was conducted using elevation, slope angle, slope aspect, and Topographic Position Index (TPI). Additionally, these types of landslide movement were compared across three geological units: granite, gneiss, and schist. As a result, 7,967 landslides were manually classified by movement types within the 234 km2 study area. The number of slide-flow (un-channeled) was 4,076, representing a proportion of 51 % of total landslides identified in the study area. In addition, the results of the topographic analysis confirmed that slide-flow (un-channeled) frequently occurred on the upper slope and ridge at elevations of 600 to 1,000 m and on slopes with angles of 25 to 35 degrees. Although the number of slide-flow (Flood) was relatively small, it was confirmed that the landslide mass flowed downslope from ridges to valleys, resulting in a larger area per landslide compared to other movement types. The distribution of landslides by movement type and geology revealed that the granite area had a larger average landslide area than other geological units, except for slide-flow (Flood). This is considered to be caused by the presence of weathered materials covering the bedrock in the granite area.

Keywords: Remote sensing, Topographic interpretation, Shallow landslide distribution map, Geological characteristics, Da Nang City

Topic: Topic B: Applications of Remote Sensing