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An avalanche is a mass of snow, ice, and debris flowing and sliding rapidly down a steep slope (Colorado Natural Hazards Mitigation Plan, 2013, p. 3-138). An avalanche is defined in Colorado state statutes as a “geologic hazard.”
According to the Colorado Avalanche Information Center (CAIC), avalanches have killed more people in Colorado than any other natural hazard since 1950, and Colorado accounts for one-third of all avalanche deaths in the United States. Most deaths are backcountry recreationists and they most commonly occur on the steep mountain slopes in Western Colorado between November and April. Recorded property damage is relatively low, with a total of $313,500 over the last 50 years, suggesting good recognition and avoidance of hazardous construction in known runout zones (Colorado Natural Hazards Mitigation Plan, 2013, p. 3-147). However many highways, roads, and railroads intersect with runout zones in Colorado and avalanches remain a constant threat to transportation safety. Road closures are common at various locations across the state due to avalanche threats, damages and cleanup, or mitigation activities. These closures may disrupt commerce and isolate communities with limited road access.
Avalanches generally occur independently of other hazards, although they are often caused by increased snow pack from winter precipitation. Earthquakes, thermal changes, and blizzards are also likely to trigger avalanches. Avalanche impacts (damaged structures, loss of lives, etc.) can be similar to those resulting from landslides, mud/debris flows, and rockfalls.
Where avalanches run out in valley bottoms, they can form blockages made of snow, ice, broken trees, and/or debris that may trigger Fluvial Hazards, such as erosion, sedimentation, stream channel movement, and erosion of valley margins as the stream channel reacts to the sudden change on the valley floor.
Colorado Avalanche Information Center (CAIC)
The Colorado Avalanche Information Center is a program within the Colorado Department of Natural Resources. The program is a partnership between the Department of Natural Resources (DNR), Department of Transportation (CDOT), and the Friends of the CAIC (FoCAIC), a 501c3 organization. The mission of the CAIC is to provide avalanche information, education, and promote research for the protection of life, property, and the enhancement of the state’s economy. The CAIC website provides useful information such as statistics, maps, photos, and videos about avalanches.
