Here is a photo I took of an avalanche encounter that turned out just fine, but it was not part of a guided program and we ended up where we should not have been.
While skiing at CMH Revelstoke last week, the guides let us know, in no uncertain terms, that the avalanche conditions were very unstable. We found ourselves ripping run after run of awesome powder, but the guides directed us exactly where to ride, chose terrain conservatively, and explained much of their thought process to us skiers and snowboarders. However, I know there is much more going on behind the scenes so I asked Colani Bezzola, the Mountain Safety Manager for CMH and a 36-year veteran heli-ski guide, to share some insights into the system CMH uses to keep us safe out there.
TD: Most of the time while heli-skiing, we meet the guides, go skiing all day, and rarely do we see them dig pits or do much obvious snow stability testing while skiing. Why is that?
CB: While guiding, we continuously observe the mountain, present and recent avalanche activity, the weather, how the snow reacts while skiing and while standing in it or while approaching certain terrain features. While guiding a group of skiers we may look at the surface snow layers and do some quick surface stability tests by ski cutting on top of rolls and by digging a quick test profile. Many of these actions and observations occur continuously even if they are not obvious to you. Being aware of your surroundings and elements is how guides stay alive during a life in the mountains.
TD: So how do you fit more extensive snow profiles into the high-speed heli-ski program?
CB: To do more extensive snow profile observations and tests we need a bit more time. On any given day, one guide in each area is designated as Snow Safety Guide. He doesn't guide a group that day and dedicates his time in the field to check out terrain, runs, snowpack layers and changes with full snow profiles while also doing stability tests. He may do avalanche control and testing with explosives, look for wind-transported snow, wind loaded pockets, and check out the skiing quality in terrain that we may not have visited for a while.
TD: From what I can tell, the guides feel that just because they bomb something, it is not necessarily safe to ski. A bomb is pretty violent. How could a slope slide on a skier after not sliding under the force of a bomb?
CB: We do very limited and selective avalanche control and testing with explosives compared to ski areas or road avalanche operations. Mostly we use explosives to protect helicopter landings and pick ups and remove potential avalanche threats that may run into skiing terrain. If we deploy explosive charges on a slope and it doesn’t slide, the questions always remain:
- Have we applied the trigger (explosive) to the right spot?
- Have we "tickled" the weakness, the "sweet spot"?
- How deep is the potential unstable layer and how stiff is the slab over it?
If we cannot answer all these questions completely after a slope resists an explosive trigger, we tend to decide on the side of caution. From experience we know of avalanches that occurred naturally sometime after we deploy explosive charges, and without obvious additional trigger; as well as incidents where skiers (additional triggers) have found the "sweet spot" near places where explosives had been applied recently.
TD: Wow, snowpack is a feisty critter. Can you briefly describe how CMH guides observe and record ongoing changes in the snowpack?
CB: All avalanche, stability tests, snowpack, snow profile and weather observations, hazard and risk assessments are captured in CMH's "SnowBase" database system, shared between all our heli-ski areas, which allows the guide teams to monitor, track and recall the developments in the avalanche, snowpack and hazard history for the winter and gives them a collective tool to help make the appropriate risk management decisions on a daily, run-by-run, and pitch-by-pitch basis.
TD: If somebody is interested in snow science and avalanche forecasts, can you suggest resources for them?
Backcountry Avalanche Awareness Jamieson, Bruce. 1989, rev. 1997. Canadian Avalanche Association. Revelstoke, Canada.
Free Riding in Avalanche Terrain, Jamieson, Bruce & Jennie McDonald.. 1999. Canadian Avalanche Association. Revelstoke, Canada
The Avalanche Handbook, Dave McClung and Peter Shaerer, 1993. Third edition, 2006. Available from Mountaineers Books
Snow Sense, A Guide to Evaluating Snow Avalanche Hazard, Jill Fredston and Doug Fesler, 1994, The Mountaineers, Seattle, WA.
Staying Alive in Avalanche Terrain, Tremper, Bruce. 2001. The Mountaineers, Seattle, WA.
Avalanch.org - central site for international avalanche information centres.