Abstract

Snow avalanches are the greatest risk threatening commercial heli-skiing groups. Guides manage the risk from avalanches by selecting terrain with a low likelihood of avalanching given their evaluation of the avalanche hazard. To do so guides make critical risk management decisions each time they encounter a slope capable of producing an avalanche. This study explores the exposure of guides to start zones capable of producing avalanches of size 2 or greater. A fuzzy logic model of potential avalanche release areas was implemented employing slope gradient, ground roughness, exposure to prevailing winds and forest stem density data. A data set of 100 documented avalanche location polygons were used to validate the model and derive threshold criterion necessary to identify potential release areas. Lead guides at Canadian Mountain Holidays Galena Lodge were equipped with GPS units over the course of the 2015 to 2018 winter seasons, creating a dataset of 6500 tracked heli-skiing descents. The linear geometries of the tracks were combined with a vector model of potential avalanche release areas through an overlay analysis to quantify exposure of guides to avalanche start zones. The results of this analysis show that guides were exposed to potential avalanche release areas capable of producing a size 2 avalanche in 27.5% of the terrain they skied and chose to enter such terrain on average 19.4 times per day.

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