In the spring I have counted one hundred and thirty-six different kinds of weather inside of four and twenty hours. ~Mark Twain
Spring also means a whole lot of changes for the snow and avalanche conditions, and spring can be a most dangerous time rescuers. Last Friday there was an avalanche accident off-piste at Val d’Isère, France, which resulted in a serious and risky rescue. Fortunately the knowledge, skill, and professionalism (and probably some luck, too) of the ski patrollers saved the skier’s life. Part 1 of this two-part series focuses on the differences of wet and dry avalanches and what this means to rescuers. Part 2 will suggest how rescuers should adapt their strategies to deal with wet avalanches.
Accident: Face du Charvet E Face, 11:45 Val d’Isère April 1
The pisteurs (ski patrollers) at Val d’Isère faced a challenging and dangerous lunchtime rescue after an avalanche swept a skier down the east-facing Face du Chavert. During the rescue several additional avalanches threatened the patrollers, but they were able to reach the victim and short-haul him away in a helicopter.
American avalanche professional and ex-pat Henry Schniewind, who runs Henry’s Avalanche Talks, happened to be in the area and watched the rescue unfold. Take a look at his website to get more details including pictures and video. (If you’re going to France, especially the Val d’Isère, Tignes, or Maribel areas, be sure to go to his local avalanche talks. Even if you’re not headed to France, but you do want to learn about avalanches and if you’re willing to spend a little money, his website has some excellent on-line avalanche education through his Ride Hard Ride Safe program.)
According to Henry some new snow had fallen the night before (and three days earlier) on the 600m-tall east face of the Face du Chavert. Just before noon a small point release [I am sure it was not the first] turned into a large and wet loose snow avalanche as it cascaded down the rocky faces and chutes. The slide swept one skier from a group of five over a cliff. Ski patrollers responded and “at least” 3 or 4 additional “big” avalanches spilled down the face. During one of these avalanches the rescuers had to race to the side to escape. Henry said the roar of the avalanches was impressive. Fortunately, the patrollers dodged the avalanches and were able to reach and evacuate the injured skier but at great risk.
A Short Editorial Comment
The group’s decision, which included a “guide”, to be where they were was wrong. Guide or no guide, it was the wrong time to ski the face. It should have been an easy decision not to go. Fresh snow, rocky and east-facing terrain, light freeze overnight and intense morning sun should have triggered alarm bells. By the way, the avalanche danger was rated “marque,” which is the same as “considerable” in the North American ratings.
Wet Snow – A Different Type of Avalanche Dragon
A wet, springtime avalanche is a different beast compared to its mid-winter, dry-snow cousin. Avalanche savant Bruce Tremper summarizes these differences in his excellent book, Staying Alive In Avalanche Terrain. He writes, “Wet avalanches are triggered differently, they move differently, they’re formed by different conditions, you forecast for them differently, their deposits are different, and the scars they leave on the vegetation are different.”
Bruce goes on to point out that when it comes to how avalanches start the main difference between dry and wet snow avalanches is that dry snow avalanches are caused by overloading the strength of buried weak layers, and wet avalanches are caused by decreasing the strength of buried weak layers. In general, the primary culprit for dry avalanches is the additional stress, or load, from the weight of more new snow, wind-drifted snow, or even the weight of a skier or snowmobiler. In wet snow often it’s thaw conditions that melts bonds between snow grains, which reducing the snow’s strength that’s the culprit.
Snakes and Avalanches
For rescuers this difference is profound. In dry snow, avalanches tend to act more like a snake. Both are secretive, stealthy, and many people might say both are unpredictable. Snakes and dry avalanches are solitary and are often silent. You can travel all day and not see or hear either, but to get bit, generally you have to provoke the snake or avalanche.
Bees and Avalanches
Wet avalanches, on the other hand, are more like a swarm of angry African bees out looking for trouble. Both bees and wet avalanches are overt, conspicuous, noisy, and often come in swarms. When you see one, you’re certain to see more. It’s this fact about wet avalanches that poses a serious threat to rescuers.
Is It Safe?
In dry snow you have to find the trouble; most avalanche accidents are caused because the victim (or a friend) triggered the slide by venturing into the avalanche starting zone. As long as conditions (winds, temperature, precipitation, etc.) stay the same and other triggers (people) can be kept away, rescuers can work on avalanche debris with little or no threat from additional avalanches. In many cases, rescues can be performed with remarkably little risk.
In wet snow more accidents are caused by naturally occurring avalanches where the victim was in the wrong place at the wrong time. (Certainly, education, experience, timing and safety margins can help keep one out of harm’s way.) More often the avalanche crashes down on the traveler who might not even be in the steep slopes of the starting zone. Unlike dry snow, when conditions (sunshine, temperatures, etc) stay the same with wet snow you can count on additional avalanches. When a natural wet avalanche has resulted in an accident, rescuers – either companions or professionals – will face the immediate threat of additional avalanches. Rescues in wet avalanches can be very dangerous affairs.
Next week: Part 2. What rescuers should do when dealing with wet snow avalanches.
Any thoughts so far, or experiences to share?
Thanks for reading.