November 17th, 2012
AVALANCHE FORECASTING HISTORYZero Fatalities, by Catherine Higgins.
Alta, Utah, located on SR 210 in Little Cottonwood Canyon, is the birthplace of avalanche forecasting and avalanche control in North America.
The historic connection between Alta, SR 210 and avalanche forecasting seems fitting since the road has one of the highest Avalanche Hazard Index ratings in North America. Snowfall abundance, terrain steepness and traffic volume have combined to give the road a high avalanche rating of 766.
The current Highway Avalanche Safety Program at UDOT has evolved over seventy years to its current state of practice. In 1939, the United States Forest Service hired the first Snow Rangers and established the first program in North America devoted to the study of avalanches at Alta. Following WW II, The USFS hired Monty Atwater, now known as the Grandfather of Avalanche Forecasting, as the Snow Ranger at Alta.
During his years at Alta, Atwater conducted research on snow safety and became known as a world authority on avalanche control. He pioneered the use of military weapons which are still used by UDOT for avalanche control.
“It’s the work of all our predecessors that laid the groundwork for what we do today,” according to Liam Fitzgerald who as the Avalanche Forecaster for UDOT knows science of avalanche forecasting and avalanche safety programs. Fitzgerald administers the Avalanche Safety Program at UDOT which is based on three primary areas of focus: avalanche forecasting, control and rescue.
UDOT’s Highway Avalanche Forecasts are issued for 12 hour periods for each canyon. Forecasts are based on snow-pack structure, local weather data and accurate weather forecasts. If the forecast suggests an avalanche is likely to occur, forecasters test the snow-pack for stability. Often, the tests are carried out using military artillery. Terrain features, snow-pack structure, weather conditions, and avalanche activity from the past determine targets for military artillery.
UDOT is making efforts to move away from the use of military artillery for avalanche control. New Gaz-X exploder systems have been installed at known avalanches sites. Two of the new avalanche control systems have recently been installed in a known avalanche path called Valerie’s Slide in Little Cottonwood Canyon on the lower face of Mount Superior.
The visible part of the system is a downward-facing twelve foot long, two foot diameter tube. An underground oxygen and propane storage farm feeds the gases to exploders where the gases are mixed in preparation for firing. The units are then triggered by remote control producing a shock wave that moves through the tube.
The resulting controlled slide prevents a bigger, potentially more destructive slide. The system is a better alternative than howitzer-fired or hand dropped shells since the slide area is adjacent to Snowbird Village and SR-210. Two similar units have been in operation for two years. The new units are planned to be operable for this coming snow season. UDOT has plans to install more units next year.
Although most of the time avalanche forecasting and control efforts allow for safe travel on the canyon roads, naturally occurring avalanches occasionally reach the canyon roads while they are open. When a snow avalanche occurs, and a rescue operation is needed, UDOT forecasters assume the role of Accident Site Commander in Highway Avalanche Rescue efforts along the Wasatch Front. UDOT Avalanche Forecasters are a part of the Wasatch Backcountry Rescue organization.
This post is based partly on a presentation given by Liam Fitzgerald, the Avalanche Forecaster for UDOT.