AVALANCHE FORECASTING AND MONITORING IN THE SAN JUAN MOUNTAINS OF SW COLORADO

Avalanches are a major natural hazard in the San Juan Mountains of SW Colorado. Approximately 500 avalanches are recorded in the San Juans by the Colorado Avalanche Information Center (CAIC) each winter season. This number is estimated to be 50% of the total avalanches that occur in the region each year. Avalanches affect the major highways that pass through the San Juans and are a serious hazard to motorists and recreationalists. Avalanche forecasting began in SW Colorado in 1992. The Colorado Department of Transportation (CDOT) contracted with the CAIC to start an avalanche forecasting program as the most effective and economical method to mitigate the avalanche hazard on Highway 550 at Red Mountain Pass. The mission of the CAIC is to promote safety by reducing the impact of avalanches on recreation, industry and transportation in the state through a program of forecasting and education. Avalanche forecasting for the highways of SW Colorado is conducted on a daily basis from November 1st to May 1st. Avalanche forecasts are disseminated each morning to CDOT maintenance personnel, and government officials located near the mountain passes. These highway forecasts differ from the public backcountry forecasts in that they are only relevant for avalanche paths along highway corridors. Avalanche hazards are predicted for 24 hour periods. Recommendations for the use of avalanche mitigation are made based on current and forecasted snowpack stability evaluations. Daily snowpack observations are conducted in areas close to the starting zones of avalanche paths that affect the highways. Numerous snowpack and stability parameters are collected and analyzed to determine the spatial and temporal stability of the snowpack. Four remote weather stations, on mountain ridges above the highways, use radio telemetry to send real-time weather information to the CAIC offices. Precipitation is monitored at numerous snow study plots adjacent to the mountain passes. CDOT personnel, in collaboration with CAIC forecasters, conduct avalanche mitigation as necessary to keep the avalanche hazard along the highway corridors to a minimum. Mitigation is conducted with explosive charges designed for avalanche control as well as military artillery.