Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/nhess-2016-317
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
30 Sep 2016
Review status
This discussion paper is under review for the journal Natural Hazards and Earth System Sciences (NHESS).
Anomalous winter snow amplified earthquake induced disaster of the 2015 Langtang avalanche in Nepal
Koji Fujita1, Hiroshi Inoue2, Takeki Izumi3, Satoru Yamaguchi4, Ayako Sadakane5, Sojiro Sunako1, Kouichi Nishimura1, Walter W. Immerzeel6,7, Joseph M. Shea7, Rijan B. Kayashta8, Takanobu Sawagaki9, David F. Breashears10, Hiroshi Yagi11, and Akiko Sakai1 1Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan
2Disaster Risk Research Unit, National Research Institute for Earth Science and Disaster Prevention, Tsukuba, Japan
3Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, Hachioji, Japan
4Snow and Ice Research Center, National Research Institute for Earth Science and Disaster Resilience, Nagaoka, Japan
5Langtang Plan, Kamakura, Japan
6Department of Physical Geography, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
7International Centre for Integrated Mountain Development, Khumaltar, Kathmandu, Nepal
8School of Science, Kathmandu University, Kathmandu, Nepal
9Faculty of Social Sciences, Hosei University, Tokyo, Japan
10GlacierWorks, Marblehead, MA, USA
11Faculty of Education, Art and Science, Yamagata University, Yamagata, Japan
Abstract. Co-seismic avalanches and rock falls, and their simultaneous air blasts, which were induced by the 2015 Gorkha earthquake in Nepal, destroyed the village of Langtang. In order to reveal volume and structure of the deposit covering the village, and sequence of the multiple events, we conducted an intensive in-situ observation in October 2015. Multi-temporal digital elevation models created from photographs taken by helicopter and unmanned aerial vehicles reveal that the deposit volumes of the primary and succeeding events were 6.81 × 106 m3 and 0.84 × 106 m3, respectively. Visual investigations of the deposit and witness statements of villagers suggest that the primary event was an avalanche composed mostly of snow, while the contribution of collapsed glacier ice could account for a few percent of the total mass. Succeeding events were multiple rock falls which may have been triggered by aftershocks. From the initial deposited volume and the upper catchment area, we estimate an average snow depth of 1.56 m in the source area using density assumptions of snow and ice. This is consistent with anomalously large snow depths (1.28–1.52 m) observed at a neighboring glacier (4800–5100 m a.s.l.), which accumulated over the course of four major snowfall events since October 2014. Considering long-term observational data, probability density functions, and elevation gradients of precipitation, we conclude that this anomalous winter snow was an extreme event with a return interval of at least 100 years, which amplified or even caused the disaster induced by the 2015 Gorkha earthquake in Nepal.

Citation: Fujita, K., Inoue, H., Izumi, T., Yamaguchi, S., Sadakane, A., Sunako, S., Nishimura, K., Immerzeel, W. W., Shea, J. M., Kayashta, R. B., Sawagaki, T., Breashears, D. F., Yagi, H., and Sakai, A.: Anomalous winter snow amplified earthquake induced disaster of the 2015 Langtang avalanche in Nepal, Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2016-317, in review, 2016.
Koji Fujita et al.
Koji Fujita et al.
Koji Fujita et al.

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Short summary
We create multiple DEMs from photographs taken by helicopter and UAV, and reveal the deposit volumes over the Langtang village, which was destroyed by the Gorkha earthquake-induced avalanches. An estimated snow depth in the source area is consistent with anomalously large snow depths observed at a neighboring glacier. Comparing with a long-term observational data, we conclude that this anomalous winter snow amplified the disaster induced by the 2015 Gorkha earthquake in Nepal.
We create multiple DEMs from photographs taken by helicopter and UAV, and reveal the deposit...
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