Item: Which obs for which avalanche type?
Title: Which obs for which avalanche type?
Proceedings: 2010 International Snow Science Workshop
Authors: Bruce Jamieson * Dept. of Civil Engineering, Dept. of Geoscience, University of Calgary, Calgary AB, Canada Jürg Schweizer WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland Grant Statham Parks Canada Agency, Banff AB, Canada
Abstract: At the 2004 ISSW, Roger Atkins proposed that—early in the terrain selection process— backcountry travellers could identify which types of avalanches were likely, e.g. wind slab, persistent slab, wet avalanche. These avalanche types are analogous to a set of scenarios in traditional risk analysis. Variations on Atkins’ approach have been incorporated into some public bulletins. The types of avalanches that dominate the danger ratings are called Avalanche Types/Characters/Threats/Concerns/Situations/Problems by different groups. The latest Swiss brochure for recreation in avalanche terrain suggests different observations for the four different types of avalanche situations. To determine which observations are best for which types of avalanches, a field study was conducted in the winters of 2008-09 and 2009-10 in the Coast Mountains, Columbia Mountains and Rocky Mountains of western Canada. On each field day, an experienced field team rated the local avalanche danger, identified two dominant Avalanche Types and observed a standard set of over 20 quick field observations. The quick observations included avalanches, wind transported snow, snowfall, etc. For correlation analysis, we focused on two distinct classes of Avalanche Types: 1) Persistent Slabs, as well as 2) Wind Slabs combined with Storm Slabs. While some observations correlated with the local danger when either class of avalanches dominated the danger rating, other observations correlated best when only one of these two classes dominated the local danger rating. These results may help bulletin writers recommend that recreationists focus on certain local observations for better informed decisions.
Keywords: avalanches types, atkins’ approach