Abstract
Abstract. Recreational activities in snow-covered mountainous terrain in the backcountry account for the vast majority of avalanche accidents. Studies analyzing avalanche risk mostly rely on accident statistics without considering exposure (or the elements at risk), i.e., how many, when and where people are recreating, as data on recreational activity in the winter mountains are scarce. To fill this gap, we explored volunteered geographic information on two social media mountaineering websites – bergportal.ch and camptocamp.org. Based on these data, we present a spatiotemporal pattern of winter backcountry touring activity in the Swiss Alps and compare this with accident statistics. Geographically, activity was concentrated in Alpine regions relatively close to the main Swiss population centers in the west and north. In contrast, accidents occurred equally often in the less-frequented inner-alpine regions. Weekends, weather and avalanche conditions influenced the number of recreationists, while the odds to be involved in a severe avalanche accident did not depend on weekends or weather conditions. However, the likelihood of being involved in an accident increased with increasing avalanche danger level, but also with a more unfavorable snowpack containing persistent weak layers (also referred to as an old snow problem). In fact, the most critical situation for backcountry recreationists and professionals occurred on days and in regions when both the avalanche danger was critical and when the snowpack contained persistent weak layers. The frequently occurring geographical pattern of a more unfavorable snowpack structure also explains the relatively high proportion of accidents in the less-frequented inner-alpine regions. These results have practical implications: avalanche forecasters should clearly communicate the avalanche danger and the avalanche problem to the backcountry user, particularly if persistent weak layers are of concern. Professionals and recreationists, on the other hand, require the expertise to adjust the planning of a tour and their backcountry travel behavior depending on the avalanche danger and the avalanche problem.
Highlights
Winter sports activities in mountainous terrain – such as ski, snowboard or snowshoe touring – have become increasingly popular during recent decades (Lamprecht et al, 2008, 2014; Winkler, 2015)
Avalanche accident studies show – for instance, for countries in the European Alps – that the vast majority of avalanche accidents involving people occurred during winter sports activities in uncontrolled terrain with recreationists triggering the avalanche in most cases themselves (e.g. Valt, 2009; Jarry, 2011; Techel and Zweifel, 2013)
We explored volunteered geographic information posted on the two social-media mountaineering networks bergportal.ch and camptocamp.org
Summary
Winter sports activities in mountainous terrain – such as ski, snowboard or snowshoe touring – have become increasingly popular during recent decades (Lamprecht et al, 2008, 2014; Winkler, 2015). Valt, 2009; Jarry, 2011; Techel and Zweifel, 2013) Investigations of such human-triggered avalanches have shown that typical snowpack patterns exist. Often these accidental avalanches failed in so-called “persistent” weak layers – snow layers that were either coarse-grained, soft and had undergone temperature-gradient metamorphism or consisted of buried surface hoar (Jamieson and Geldsetzer, 1999; Schweizer and Lütschg, 2001). Based on these findings, Schweizer and Jamieson (2007) developed a field test helping recreationists
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