EMERGENCY RISK REDUCTION

The season is here again, when the local news gives a tragic story of another death from an avalanche. As I write this,  the hourly news from my trusty radio just reported two deaths in Jackson Hole, Wyoming. Avalanches kill more than 150 people throughout the world every year.  Here in British Columbia, the toll averages 11 deaths annually. The 2008-09 winter was especially tragic, with 25 deaths. Sadly, the overall trend is not decreasing, due to the popularity of ‘extreme’ outdoor winter sports.

An avalanche occurs when a mass of ice and snow breaks away from the side of a mountain and surges downhill with speed and force.   Some avalanches are small surface movements involving a minimal amount of loose snow.  Dry snow movement is called sloughing, while wet surface snow may include snowballing or pinwheeling. Slab movement involves deeper larger snow masses, and account for the deadliness associated with avalanches.

 Avalanche “triggers” can be either natural or human-induced. Natural tendencies increase the differential between layers in the snowpack, and are caused by humidity, rain, temperature, wind, pressure, etc.  This metamorphosis can occur either slowly or quickly. Most avalanches occur within 24 hours after a storm drops 12 or more inches (30 centimeters) of fresh snow. Avalanche terrain includes many factors, such as slope, wind, sun, elevation, trigger points, and other ‘terrain traps’, i.e. cliffs and icefalls.  An area that is extremely vulnerable to avalanches is where layers of wind-driven snow have delicately accumulated.

Many large avalanches today are triggered by people who are skiing, snowboarding, hiking, or snowmobiling,   with the latter accounting for 40% of the deaths.   The majority of the 25 killed in 2008-09 in BC were recreational snowmobilers.

People that access areas where avalanches may occur should know if the location has been declared to be safe.  Eleven terrain parameters go into an “Avalanche Terrain Exposure Scale” (ATES), which consists of three categories to inform travelers:   Class 1: Simple – low slope angle with stable snow and low avalanche risk. Class 2: Challenging –  moderate slope with defined avalanche paths, and may contain terrain traps.  Class 3: Complex – large steep terrain with multiple avalanche paths, complicated glacial travel, with terrain traps.

People are encouraged to never travel into risky areas alone. After an avalanche, time is critical. If someone is found less than 18 minutes after being buried, survival rate is 91%. After 35 minutes, the rate drops to 30%. Therefore, the most effective rescue is Companion Rescue.  Groups travelling into the backcountry should carry transceivers, probes, and shovels. Never ski or snowboard into ‘out of bounds’ areas of ski resorts, and if you are alone on trails at a ski mountain where there’s a risk of avalanches, let someone know your plans.

When a slab of snow begins to move down the mountain, it can reach speeds of 80 miles per hour (130 kilometers). Escape is critical.  If caught in an avalanche, move 45 degrees across the slide, trying to ski or ‘swim’ out on your back. Drop all heavy bags, poles, etc. Always wear a transceiver beacon on “Send” mode.  Rescuers immediately turn their beacons to “Receive” mode, and use various patterns for searching, probing, and digging.

This is only a cursory overview. If you plan to travel into an area where the avalanche risk is elevated, I recommend a short, excellent, and free on-line course through the Canadian Avalanche Center. The link is  http://www.avalanche.ca/cac/training/online-course. This will help you have a safe and enjoyable trip into your winter wonderland.