CAIC: Colorado Avalanche Information Center

2020/03/24 - Colorado - Waterfall Canyon, south of Ophir

Published 2020/04/05 by Jeff Davis, Bill Nalli - Forecast Staff, Colorado Avalanche Information Center

Avalanche Details

  • Location: Waterfall Canyon, south of Ophir
  • State: Colorado
  • Date: 2020/03/24
  • Time: 1:30 PM
  • Summary Description: 1 backcountry tourer caught, injured
  • Primary Activity: Backcountry Tourer
  • Primary Travel Mode: Snowboard
  • Location Setting: Backcountry


  • Caught: 1
  • Partially Buried, Non-Critical: 0
  • Partially Buried, Critical: 0
  • Fully Buried: 0
  • Injured: 1
  • Killed: 0


  • Type: SS
  • Trigger: AR - Snowboarder
  • Trigger (subcode): u - An unintentional release
  • Size - Relative to Path: R3
  • Size - Destructive Force: D2
  • Sliding Surface: O - Within Old Snow


  • Slope Aspect: NW
  • Site Elevation: 11500 ft
  • Slope Angle: 40 °
  • Slope Characteristic: Planar Slope,Sparse Trees

Avalanche Comments

The avalanche was a soft-slab unintentionally triggered by a backcountry snowboarder. The avalanche was medium relative to path and large enough to bury, injure or kill a person. It failed in a layer of depth hoar and gouged to the ground in many places (SS-ARu-R3D2-O). The height of the crown face ranged from 18 to 36 inches. This was a persistent slab avalanche. 

The avalanche released below treeline on a sparsely-treed west-northwest-facing slope around 40 degrees in steepness. The party involved described the avalanche as large moving blocks of snow. The debris ran through a densely treed slope, a gully, and then over a bench approximately 600 vertical feet below. The debris was over 2 meters deep in places. 

Backcountry Avalanche Forecast

The Colorado Avalanche Information Center’s (CAIC) backcountry avalanche forecast for the North San Juan zone on March 24, 2020 rated the avalanche danger as MODERATE (level 2 of 5) at all elevations. Persistent Slab avalanches were listed as the primary avalanche problem type, and highlighted on west, northwest, north, northeast and east aspects. The likelihood of triggering was possible and the potential size was large. The CAIC summary for the North San Juan Zone read: 

Two to four inches of new snowfall yesterday and overnight and moderate west to southwest wind has amounted to a small refresh to the surface without increasing the hazard much.  Triggering an avalanche however on west through north to east-facing slopes remains possible. A layer of weak, faceted snow that formed at the surface in Late-February is now buried two to four feet deep at all elevations on these aspects. Many recent rider-triggered slides occurred in the last few days (Obs1, Obs2, Obs3).

The further away from the main loading event last week, the more stubborn avalanches have gotten. Obvious signs of instability like cracking and collapsing may not be present until it’s too late but if you manage to find that “not-so-sweet” spot, slides will be large enough to bury, injure or kill you. Avoid likely trigger spots like smooth rounded pillows below ridges or thinner zones near small rocky outcrops. Minimize exposure by riding one at a time and get well out of the way at the bottom. As is normal this time of year, when the sun peeks out between breaks in the clouds watch for another round of small wet avalanches on southerlies. Safer riding can be found on wind sheltered slopes less than 35 degrees out of the sun.

Weather Summary

February was dry, with lower than normal snowfall in the Ophir area. Telluride Mountain Resort (four miles northeast) measured 30 inches of snowfall. That was 68% of the 30 year average. Much of the snowfall came at the beginning of February and the last two weeks were dry with clear skies and mild temperatures. March started with a small storm with little wind on March 2, and two more small storms on March 9 and 14. On March 19 and 20 a larger storm deposited 15 to 20 inches of snow containing 1.5 to 1.7 inches of snow water equivalent (SWE). An additional four inches of snow fell in the area prior to the avalanche, bringing the total SWE to 2 inches in five days. There were moderate south winds during the storm.

Snowpack Summary

Very little snow fell in the San Juan Mountains before Thanksgiving. The majority of the early season snowpack developed during the last six weeks of 2019 and the snowpack was generally stronger and deeper than average at the start of 2020. Strong winds in January drifted snow into thick, dense layers in some areas, while eroding others and leaving a total snowpack depth less than four feet deep. February was dry and cool, which promoted the growth of faceted snow crystals and depth hoar in the shallow snow areas.

By the end of February, many shady slopes below 11,500 feet developed a weak, cohesionless snowpack. Near the surface, diurnal recrystallization formed small faceted grains. Multiple small storms throughout the month of March buried the weak surface snow and increased slab depth, but did not overload the weak layer. Observers reported few avalanches. 

In the days prior to the accident, the slab formed in March increased to two to three feet. Wind drifts were deepest on slopes with a northerly aspect. There were 20 natural and triggered avalanches reported in the North San Juan zone between March 19 and 20. These avalanches failed on either the near-surface faceted layer or depth hoar.

Events Leading to the Avalanche

Rider 1 joined Rider 2 at his house in Ophir to discuss their plan for the day over coffee. At 8:15 AM they watched an avalanche run naturally on Yellow Mountain. They left the house at 8:40 AM. Their plan was to “ride something mellow” in an area known as Nevada Basin, meet Rider 2’s girlfriend in town, and continue touring.

The pair ascended the well-used uptrack on the eastern side of Waterfall Canyon. On the way up they looked at an avalanche on a north-facing slope, triggered by backcountry tourers two days prior. They rode down a north-east facing, heavily treed slope in Nevada Basin. At the bottom they discussed the “weird” feeling of the snow due to warm temperatures. Rider 2’s girlfriend was unable to join them, so the pair hustled back up the uptrack for another run.

On the second ascent the pair noted how many tracks there were in popular descents. They watched another group of backcountry riders (Group 2) descend a steep northwest facing slope known as The Banker. Riders 1 and 2 decided to descend into The Banker from a lower-elevation, lower-angled, and lower-trafficked area known as Sugar Trees. They descended together riding spaced out through dense trees and stopped at the top of a steep, open slope. They were higher and further skier’s right than they initially planned.

Rider 1 said he would make a slope cut and keep riding. They did not discuss the plan further, but Rider 2 planned to descend further to skier’s left. Rider 1 made a slope cut to skier's right across the apex of the slope, then began making turns down the slope.

Accident Summary

Rider 1 triggered the avalanche on his second or third turn below the slope cut. The crown of the avalanche broke at the feet of Rider 2. Rider 2 yelled “avalanche, avalanche!” The slide caught Rider 1 and quickly swept him out of sight. They described the avalanche as “breaking in large chunks” and “very fast moving.” 

The avalanche carried Rider 1 approximately 400 vertical feet through sparse trees. He hit one of the largest trees on the slope, approximately 20 inches in diameter. His head was downhill, with his legs and chest wrapped around the tree. Avalanche debris packed on the uphill side of the tree. Rider 1 was left in the tree, supported by a pile of avalanche debris when the avalanche stopped.

Rescue Summary

Rider 1 called Rider 2 on their two-way radios screaming for help. Rider 2 was relieved Rider 1 was not buried. He knew his friend was seriously injured. Rider 2 assessed the slope for other hazards, then proceeded down the bed surface of the avalanche.

At least three other groups of backcountry tourers witnessed the avalanche and made contact with Riders 1 and 2 via radio. Group 1 was across Waterfall Canyon, Group 2 had finished their descent of the The Banker and was  approximately 200 feet below the toe of the avalanche, and Group 3 was ascending the uptrack to the northeast. 

Residents in Ophir also heard the radio traffic and contacted search and rescue. San Miguel Search and Rescue (SMSAR) dispatched a team of rescuers and a helicopter. Two Ophir residents quickly started up the uptrack with a rescue sled. Both were very experienced backcountry travelers. Skier 3 was a member of SMSAR and an emergency room doctor, and Skier 4 a mountain guide.

Rider 2 reached his friend. He cut off Rider 1’s backpack and completed a spinal assessment. Rider 2 dug away the avalanche debris supporting Rider 1. Rider 1 was able to push himself off the tree, and landed face-down in the snow. Rider 2 cleared snow away from Rider 1’s face and attempted to keep him comfortable.

Members of Group 2 and 3 arrived shortly after Rider 2. Some of the group had advanced medical and rescue training. They began first aid and prepared to evacuate Rider 1. The group built an improvised rescue sled from a snowboard and space blankets. They slowly moved him downhill on the sled.

Skiers 3 and 4 arrived about an hour after the avalanche. Skier 3 reassessed Rider 1. The group moved him to the rescue sled. They carried Rider 1 to a bench in the terrain and waited for the helicopter dispatched by SMSAR. The helicopter landed about 3 hours after the avalanche released and flew Rider 1 to the Telluride airport. He was transferred to a medical helicopter and flown to a hospital in Grand Junction.


Rider 1 sustained significant, life-threatening injuries. It was approximately three and a half hours from the time of the avalanche to the time Rider 1 was in a medical helicopter. The fast actions taken by other groups in the area, their medical skill and experience, and the availability of a helicopter likely saved Rider 1’s life.

Carrying 2-way radios provided valuable communication and likely decreased the overall rescue time. There is little or no cell service in the Ophir area. The Telluride Mountain Club established channels and protocols for 2-way radio use in the backcountry around Telluride, including Ophir. Groups 1, 2, and 3 were able to communicate with Rider 2 and respond to the accident. Ophir residents often listen to their radios while at home, and were able to immediately alert authorities about the avalanche.

Until the middle of March, there were unusually few backcountry avalanches in the North San Juan Zone. In February there was a long period of Low (Level 1 of 5) avalanche danger, and local backcountry users had grown accustomed to traveling in complex avalanche terrain without much avalanche hazard. Riders 1 and 2 explained that the “mellow” avalanche season and spring-time weather had an impact on their route choice and hazard assessment for the day. However, they knew that multiple human-triggered avalanches occurred in the Ophir area in the five days prior to the accident, all on similar slopes and elevations. Several of the avalanches were among the largest human-triggered avalanches of the season.

This accident occurred against the backdrop of the COVID-19 pandemic. In the weeks prior to the accident there was a significant increase in the number of people traveling in the backcountry. Easily accessible terrain saw heavier than normal traffic. While climbing the second time, the pair watched another group descend their intended area. They changed plans to find untracked snow, and chose terrain they were unfamiliar with.

San Miguel County had begun closing public buildings and encouraging “social distancing” on or before March 13. Almost 50 people responded and were involved in this rescue. At times they were unable to maintain the recommended 6-foot spacing for social distancing. The COVID-19 pandemic added an additional risk to rescuers.

On March 8, 2011, two backcountry tourers triggered and were caught in an avalanche on this same slope. One rider was partially buried, one fully buried, but neither were injured.




Image Missing
Figure 9: A snow profile in the crown face of the avalanche in Waterfall Canyon. Observed on March 25, 2020.