2025 Volume 87 Issue 6 Pages 347-359
In February 2025, an avalanche in Fukushima Prefecture was analyzed using Airborne Laser Scanning (ALS) to determine its quantitative morphological characteristics. The study found a small-scale, slab dry snow avalanche of the flow type. The site was a leeward slope influenced by strong westerly winds, with grass and shrub vegetation offering minimal avalanche suppression. A significant snowdrift, up to 10.0 m deep, was located near the initiation zone. The initiation zone had a slope of 40-45°, while the track and deposition zone were 20-25°, with an angle of elevation around 25°．The initiation zone was an elongated 150 m wide, and the track and deposition zone formed a slightly fan shape due to topography, with a flow length of 100-130 m. The avalanche’s overall appearance was rectangular. The initiation layer thickness reaching 4.0-9.0 m in some areas, with the 9.0 m attributed to the snowdrift. The avalanche involved the continuous collapse of the entire snowpack and surface layer across the 150 m width, with debris deposited as slabs directly below the initiation zone. Notable features included clear identification of initiation and stopping points and a long 76.6 m crack in the upper initiation zone, which remained uncollapsed, a rare occurrence given it is about half the avalanche's width.
