Avalanches are quite common in Colorado’s Rocky Mountains. They can occur anywhere there is a sizeable amount of snow and steep slopes, meaning most of Colorado’s High Country (from 10,000 to 13,000 feet) is prone to avalanches. The massive snow slides are extremely dangerous; between 1859 and 2006, avalanches killed at least 700 people in the state.

Although education and forecasting have greatly reduced the death rate in recent decades, avalanches remain a danger. The winter of 2020–21 tied for the deadliest avalanche season in the United States, with twelve of the year’s thirty-seven fatalities occurring in Colorado.

Avalanche research and forecasting in the state began with the rise of Colorado’s downhill ski industry and the construction of public ski areas on National Forests along the Front Range in the 1930s. From its origin, avalanche research evolved from a niche field conducted primarily by US Forest Service staff to a state-funded, full-time avalanche forecasting center that helps us better understand the phenomena and plan accordingly.

Causes

On steep, snowy slopes, a variety of natural conditions, including temperature and type of snowpack, can create avalanche scenarios. Once the conditions are right, all that is needed is a trigger, which is usually a person or vehicle. Intense snowstorms with high winds can blow excessive amounts of snow from one side of a mountain to the other, creating a huge snowpack susceptible to gravity. Or, a layer of snow freezes and accumulates fresh snow on top that can easily be released.

Signs of avalanche conditions include cracks in the top layer of snow and snow that settles suddenly when walked upon, usually making a “whumpf” sound. Areas where avalanches have recently occurred are prone to more avalanches, as are areas that have recently received a lot of snow and then experienced rapidly warming temperatures.

More than 90 percent of fatal avalanches are triggered by the victim or someone in the victim’s party. Avalanches can be triggered by a person walking or skiing on unstable snow, or by vibrations from vehicles such as snowmobiles and ATVs. Survival odds for those trapped in an avalanche plummet after about fifteen minutes. For this reason, experts recommend that backcountry-goers have a transceiver, shovel, and probe with them in case they need to find someone and dig them out or signal for help themselves.

History

The Nuche (Ute people), who lived in the mountains of Colorado for centuries before the arrival of whites, were familiar with avalanches and referred to them as “yogöchaykw(a)” (yo-go-CHAI-ka). Generations of experience taught them how to avoid areas prone to destructive slides.

By contrast, most white miners who flooded the Colorado High Country in the mid-nineteenth century had no experience with avalanches. That changed quickly. The first recorded avalanche fatality in Colorado Territory occurred on March 6, 1861, about twenty miles southwest of Georgetown. The following year, a man was killed when an avalanche hit his party near Cochetopa Pass. Between 1880 and 1890, when silver strikes drew thousands of people to the Colorado Rockies, avalanches killed more than 140 people.

The heavy mining era between 1860 and 1900 was the deadliest avalanche period in Colorado history, with 442 recorded deaths. One of the worst instances occurred near Silver Plume in February 1899, when an avalanche bulldozed a group of miners’ cabins. Ten people were killed, including two children. Colorado’s deadliest avalanche season came in 1915-16, when twenty people were killed statewide.

There were some close calls as well. In mid-May 1874, a miner named Charles Roach was carried some 1,300 feet down McClellan Mountain south of Silver Plume by what the Golden Weekly Globe described as “an avalanche of snow, sixty feet wide[and] twenty feet deep.” Miraculously, he survived. So did Frank Ryan, a miner who, in January 1906, made the poor decision to cut across some deep snow above a mine on Bull Hill, west of Twin Lakes. According to the Twin Lakes Miner, Ryan triggered an avalanche that flung him down 600 feet and over several cliffs before embedding him in a snowbank, where he was rescued.

Avalanches not only killed people but were also industrial saboteurs, obliterating infrastructure and bringing all-important railroad traffic to a halt. In April 1885, a train carrying sixty workers on the Denver, South Park & Pacific Railroad sped through a snow bank and triggered an avalanche that buried the train, killing at least one person aboard. Avalanches routinely delayed freight and passenger service in the winter; in February 1899, the Eagle County Examiner apologized for not getting issues to its readers on time, owing to “tremendous snowslides” that had blocked trains and killed workers across the High Country railways.

While avalanches were considered a routine hazard of mountain mining and transportation, the growing popularity of skiing and other mountain-based activities in the twentieth century prompted state and federal authorities to do more to keep people safe in avalanche country.

Notable Avalanches in Colorado History

1902 Telluride Avalanche Series →

1926 Black Bear Slide →

Avalanche Research in Colorado

In the winter of 1937–38, during the construction of a ski lift in Alta, Utah, the US Forest Service funded an observer to monitor weather, snowfall, and avalanches. The field expanded to Colorado in 1949, when a survey by Swiss mountaineer and scientist André Roch changed how the Forest Service researched avalanches in the American West. In his report, Roch found that the West has three different winter climate zones that produce different snowpacks and avalanche characteristics. Roch outlined how the Colorado High Country, ranging from 10,000 to 13,000 feet in elevation, reflected a distinct and more volatile avalanche environment than the mountains in Utah.

Realizing it needed avalanche stations in Colorado, the Forest Service established a weather observation station at Berthoud Pass, along the Front Range between Empire and Winter Park. Dick Stillman, a USFS Snow Ranger, and Whitney Borland, hydrologist and member of the National Ski Patrol, set up the station to monitor weather and climate patterns. Instruments recorded wind direction and speed, temperature, hourly and daily snowfall, the water content of snow, snow settlement, and depth of the snowpack. The researchers themselves recorded sky conditions, avalanche occurrence, and the size of avalanches.

The rangers at Berthoud Pass documented the occurrence of “deep slab” and “delayed release” avalanches, which are characteristic of Colorado’s High-Alpine climate zone. In other states, excess weight from snowfall causes avalanches to occur sooner after a storm. But Colorado’s drier, less dense snowfall doesn’t often overpower a weak layer within the snowpack until multiple storms bring enough weight—or a winter recreationist ventures onto the slope. This means that in Colorado, the avalanche threat remains high even after a storm.

The researchers at Berthoud Pass sent their findings to the Alta Avalanche Study Center, which was the hub for Forest Service avalanche research from the 1940s through the 1960s. After losing funding, however, the Alta station shifted to more of an administrative center that distributed information about avalanches to the public. In the early 1970s, the Rocky Mountain Research Station in Fort Collins became the new hub of avalanche research. A growing cadre of snow rangers and scientists developed new ways of recording and broadcasting avalanche conditions.

Advances in Avalanche Research

From 1971 onward, avalanche research in Colorado looked characteristically different than the early snow ranger years. Ski patrollers largely took over avalanche mitigation in ski areas and resorts, so Forest Service staff and university researchers shifted their focus to protecting resort infrastructure and communicating avalanche hazards to protect recreationists. They did this through two major projects: the Forest Service’s Alpine Snow and Avalanche Research Project, and the San Juan Avalanche Project, run by the University of Colorado’s Institute of Arctic and Alpine Research (INSTAAR).

These projects created a concentration of avalanche experts in Colorado. The Alpine Snow and Avalanche Research Project, headed by veteran researcher Mario “Pete” Martinelli, expanded the network of weather stations in Colorado and recorded information with the help of longtime snow rangers, observers, and scientists like Ron Perla, Arthur Judson, Don Bachman, and Richard Sommerfeld.

The San Juan Avalanche Project, headed by former Alta Snow Ranger Ed LaChapelle, employed Bachman’s expertise in monitoring avalanche conditions to observe the effects of increased snowfall on roadways and wildlife. These researchers also ushered in the next generation of avalanche experts: Knox Williams, a newly graduated meteorologist, joined Arthur Judson in Fort Collins, and Betsy and Richard Armstrong, students of LaChapelle, moved to Silverton to participate in the San Juans project. By placing young and old researchers in the San Juan Mountains, a range notorious for avalanches, INSTAAR concentrated experts in a rich living laboratory that produced knowledge about a range of topics surrounding the hazard.

In conjunction with avalanche research in other western states, these projects helped facilitate the growth of a small but crucial scientific community studying avalanches. Eventually, there was enough data to design a forecasting system.

Forecasting Avalanches

In the 1970s, snow ranger and Fort Collins avalanche specialist Arthur Judson envisioned using databases, statistics, and weather observations to create a state-specific avalanche forecasting center. Judson created a database called “The Westwide Network,” which stored past weather and avalanche data recorded at forty-two weather stations across Colorado and the West. This provided a baseline hub for mountain weather and climate data.

Judson understood that avalanche forecasting was a practice in statistics and probabilities. Collecting as much data as possible, he established the Colorado Avalanche Warning Program in 1973. This program monitored the same data as early snow rangers, but it was bolstered by a trove of new resources, such as the Westwide Network, field observers, National Weather Service (NWS) staff, industry stakeholders, and officials with the Colorado Highway Department (now the Colorado Department of Transportation).  

The Colorado Avalanche Warning Program broadcasted warnings through the NWS communication network, reaching radio stations, newspapers, and television channels. The forecasts listed a time, location, projected end time, and a brief explanation of the warning’s nature. Judson’s statistical forecasting laid the foundation for future western avalanche forecasting centers.

The Colorado Avalanche Information Center

Due to budget cuts and shifting priorities in the Forest Service in the early 1980s, the agency cut funding to the Colorado Avalanche Warning Program and the project dissolved in 1983. Later that year, however, Knox Williams, Betsy Armstrong, and Barbara Welles secured office space and grant funding to establish the Colorado Avalanche Information Center (CAIC), the nation’s first independent, state-specific avalanche forecasting center.

Taking theories developed by Judson and his peers, the CAIC expanded the avalanche research community’s ability to reach Colorado’s public. It maintained ties with industry, recreation stakeholders, and state and federal agencies. Through publicly broadcasted forecasts, literature, and outreach efforts to increase avalanche awareness, the CAIC established itself as an essential entity for public safety. This importance was reiterated in 1992 when CDOT snowplow driver Eddie Imel was killed in an avalanche on US Highway 550 in the San Juans. The following year, CDOT partnered with the CAIC to keep its drivers in the know.

Today’s avalanche forecasts break up the state’s mountain ranges into three elevations: “below treeline,” “near treeline,” and “above treeline,” and highlight distinct hazards in all directions within these elevations, referred to as “avalanche problems.” Through this work, the CAIC has brought Judson’s vision of a Colorado-specific avalanche forecasting center into the present.

Effects of Research and Forecasting

Avalanche research and forecasting over the course of the twentieth century has undoubtedly made Colorado’s winter backcountry much safer. Technology, such as personal transceivers that can help locate people trapped under the snow, has also given recreators and rescuers more tools to mitigate the avalanche threat.

Avalanche fatalities have never returned to their mining-era peak, even though they spiked again during backcountry visitation booms in the 1980s and 1990s (at least 110 people were killed in that span). Annual avalanche fatalities dropped back down in the 2000s, reflecting the effectiveness of past research and modern education campaigns. Today, avalanches only kill around six people per year in Colorado and about two dozen nationwide.

The history of avalanches in Colorado illustrates the uncontrollable and deadly nature of these events and the power of applied scientific research to make them less deadly over time. Even though there are far more people plying Colorado’s winter backcountry today than in 1860, the threat of death by an avalanche is much lower today.

However, as the deadly 2020–21 season shows, people still trigger and die in avalanches in Colorado, often in the same ways they did in the past. No matter how much experience someone has, winter travelers to the High Country should always proceed with extreme caution.