Title Study of a large-scale dry slab avalanche and the extent of damage to a cedar forest in the Makunosawa Valley, Myoko, Japan
Author Takeuchi, Y.; Torita, H.; Nishimura, K.; Hirashima, H.
Author Affil Takeuchi, Y., Tohkamachi Experimental Station, Forestry and Forest Products Research Institute, Tohkamachi, Japan. Other: Hokkaido Research Organization, Japan; Nagoya University, Japan; National Research Institute for Earth Science and Disaster Prevention, Japan
Source Annals of Glaciology, 52(58), p.119- 128, . Publisher: International Glaciological Society, Cambridge, United Kingdom. ISSN: 0260-3055
Publication Date 2011
Notes In English. 32 refs. GeoRef Acc. No: 310185
Index Terms avalanches; damage; ecology; mass movements (geology); models; simulation; environment simulation; snow; stresses; velocity; Japan--Myoko Mountain; Asia; Far East; forests; geophones; Honshu; Japan; Makunosawa Valley; mass movements; Myoko Mountain; Niigata Japan; snowpack; stress
Abstract Accurate measurements of snow avalanche flows in forests are rare. To understand how forests can stop avalanches, we study a mixed flowing avalanche that stopped in a cedar (Cryptomeria japonica) forest in Japan. The large-scale dry slab avalanche occurred in the Makunosawa valley in Myoko on 17 February 2008 and damaged many trees. The site contains a geophone and other devices to detect avalanche activity. A nearby meteorological station provides weather information. Post-event observations were made of the scale of the avalanche and tree damage. These showed that the avalanche released from the east-southeast-facing slope at 1700 ma.s.l. Snow debris reached ~770 ma.s.l; the horizontal runout distance was ~3000 m. The area of the runout zone was 10 ha, and the snow water equivalent of debris was 400-1500 mm. The mass of the avalanche was roughly estimated at 5-10107 kg (1-2105 m3). We used snowpack simulation models to estimate the height of the fracture zone. The simulations revealed that a faceted snow layer formed at 2 m and the stability index was 0.5 (poor) at the time of the avalanche release, due to heavy snowfall. We estimated the avalanche velocity from the bending stress of the broken cedar trees, in order to verify the effect of forests in reducing avalanche velocity. The avalanche was estimated to flow into the forest at a velocity of 26-31 m s-1, with a 17 m high powder snow layer and a dense-flow layer 2 m in height. It appears to have slowed down and stopped at 130 m after penetrating the upper edge of the forest.
Publication Type journal article
Record ID 65007378