Rockfall hazard in the Daisekkei Valley, the northern Japanese Alps, on 11 August 2005 |
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| Authors: | Yoshihiko Kariya Go Sato Kuniyasu Mokudai Jiro Komori Masaki Ishii Ryoko Nishii Yosuke Miyazawa Noriko Tsumura |
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| Institution: | (1) Department of Earth Sciences, Chiba University, 1-33 Yayoi-cho, Inage Chiba, 263-8522, Japan;(2) Geological Museum, Geological Survey of Japan, 1-1 Higashi, Tsukuba Ibaraki, 305-8567, Japan;(3) Institute of Natural Sciences, Nihon University, 3-25-40 Sakurajosui, Setagaya Tokyo 156-8550, Japan;(4) Hokuyo General Construction Co. Ltd., 5377-1 Yashiro, Omachi Nagano, 398-0003, Japan;(5) Present address: Nagano Prefectural Government, 692-2 Habashita Minaminagano, Nagano 380-8570, Japan;(6) Graduate School of Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei Tokyo, 184-8501, Japan;(7) Present address: Graduate School of University of Tsukuba, 1-1 Tennodai, Tsukuba Ibaraki, 305-8577, Japan |
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| Abstract: | This paper describes a rockfall event in the Daisekkei Valley of Mount Shirouma-dake (2,932 m), the northern Japanese Alps.
The rockfall occurred on a steep cliff comprising well-jointed felsites and produced debris of ≥8,000 m3. Most debris was deposited on an elongated snowpatch located immediately beneath the cliff, and it caused casualties among
people who were trekking along a trail on the snowpatch. Additionally, a large rock block slipped 1 km on the snowpatch. The
rockfall could have been due to the differential retreat of the rockwall, which contains areas of high- and low-density joints.
Seasonal and diurnal freeze–thaw activities and snow avalanches and wash appear to be important factors responsible for the
retreat. Although some rock blocks that can collapse further remain on the rockwall, the position of the mountain trail in
the Daisekkei Valley is fixed. Fundamental reform of tourism systems for climbers, including education on natural hazards,
is required. |
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| Keywords: | Rockfall Alpine landscape Snowpatch Northern Japanese Alps Japan |
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