Geomorphological features of the time lag landslide
Abstract
In the relief activity at the landslide disaster, it is one of the most important to watch out for a secondary landslide. We also have to pay attention to the landslide witch occurs in a time lag from a cause such as rainfall and earthquakes (the time lag landslide). In this research, we targeted two large-scale time lag landslides in Japan. We considered the cause of the time lag by clarifying the geomorphic features around the landslides.
The targets of this research are the landslide in the Ono area, Oita prefecture which occurred at the northern Kyushu heavy rain, 2017 (Ono landslide) and the landslide which occurred in the Yabakei area, Oita Prefecture, 2018 (Yabakei landslide). The Ono landslide is large-scale landslide (about 24 million cubic meter) which occurred about 14 hours after the peak of rain, and 1 person was killed. The Yabakei landslide (about 6 million cubic meter) occurred suddenly without the clear cause such as rainfall and earthquakes, and 6 persons were killed. We compared the geomorphological features before and after the landslide disasters based on the digital elevation models (DEMs). The DEMs after the landslide measured by UAV (Unmanned aerial vehicle). Although both landslides had a deep slip surface (Ono landslide is about 24 m depth, and Yabakei landslide is about 20 m depth), the whole slope did not collapse but only the upper part of a slope had collapsed. Both landslide bodies consisted of secondary sediments mainly. And the both landslides are distributed in the place that the landslide occurred in the past (landslide topography). The landslide topography collects surface water and centralized ground water. It is thought that the time lag landslide occurred owing to the ground water. We need to consider the following in the future for the safe relief activity. 1st is the extraction of geomorphological danger area where the time lag landslide occurs easily, 2nd is the clarifying the observation targets for understanding the time lag landslide, and 3rd is the deciding till when we have to watch out the time lag landslide after the landslide event.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMNH33D0942D
- Keywords:
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- 1810 Debris flow and landslides;
- HYDROLOGY;
- 1826 Geomorphology: hillslope;
- HYDROLOGY;
- 4306 Multihazards;
- NATURAL HAZARDS;
- 7212 Earthquake ground motions and engineering seismology;
- SEISMOLOGY