Reto Sterchi, Pascal Haegeli, Clair Israelson
Proceedings of 2016 International Snow Science Workshop in Breckenridge, CO, 838-845
Publication year: 2016


Guides of commercial backcountry skiing operations manage the physical risk from avalanches by assessing the local avalanche hazard and carefully choosing terrain and travel procedures to keep the residual risk at an acceptable level. A daily evaluation of predefined ski runs by the guiding team about whether the particular terrain is open or closed for guest skiing under the expected avalanche conditions represents the foundation for all subsequent guiding decisions during the daily skiing program. This study uses daily hazard assessments and run list records from a heli-skiing operation to quantitatively explore patterns in large-scale terrain preferences under different avalanche hazard conditions. Our data set spans four winters (2012/13 to 2015/16) with a total of 339 days and 93,647 documented run list ratings. The patterns in the daily terrain preferences revealed by our analysis provide interesting insights on how professional mountain guides deal with different avalanche situations. Our visualization of the 2013/14 winter season shows that both daily run list ratings for different terrain categories and run usage were closely linked to the avalanche hazard rating and avalanche character. Different ski line categories on a run were progressively opened or closed with decreasing and increasing hazard level, respectively. Using the entire data set of four winters, we show that runs with more options are skied earlier in the season and more frequently skied for the rest of the season. Contrasting run use on days with and without persistent avalanche problems, we see that both repeated use of terrain that was skied previously and the number of run passes per group on the same ski run are higher on days with persistent avalanche problems and groups tend to use the same runs more frequently.