Big questions loom after inspection of Grizzly Creek Fire burn scar

Flash floods and debris flows are big threats in Glenwood Canyon going into spring, summer a year after wildfire

Flames can be seen through billowing smoke from the Grizzly Creek Fire on Monday, August 24, 2020. (Kelsey Brunner/The Aspen Times)

The Grizzly Creek Fire covered 32,631 acres before it was officially deemed contained Dec. 18. It shut down Interstate 70 for two weeks after it ignited on Aug. 10. It threatened Glenwood Springs’ water supply and forced the closure of popular hiking trails and rafting put-ins.

The disruption likely isn’t finished.

“We’re going to learn a lot this summer,” said Steve Hunter, a former engineer with the White River National Forest and member of the Burn Area Emergency Response team, or BAER. That group of scientists and specialists started assessing the Grizzly Creek burn area for soil burn severity and potential problems areas for flooding and debris flows even before the fire was out.

Hunter discussed the role of the BAER team and the major issues facing the Grizzly Creek Fire burn scar during a videoconference Thursday night hosted by Roaring Fork Conservancy, a Basalt nonprofit that explores all issues related to water in the Roaring Fork Valley.

The BAER team’s work helped determined that 12% of the terrain within the perimeter of the fire suffered a high level of burn severity. That means all or nearly all of the pre-fire ground cover and surface organic matter was consumed. The soil became hardened and will shed water instead of absorb it.

Another 43% of the terrain suffered moderate burn severity while 33% of terrain sustained low severity and 12% was unburned.

The White River National Forest’s Burn Area Emergency Response team produced this map showing the soil burn severity during the Grizzly Creek Fire last August. The areas in red were most severely impacted. Yellow was moderately impacted.
Courtesy image

Firefighters did a remarkable job protecting two of the major drainages from the fire. No Name Creek, which drains down into a residential area, was only 8% burned. Grizzly Creek was 14% burned. Terrain in other catchments was up to 40% burned.

The areas that suffered the most fire damage may be most susceptible to flooding, debris flows and rock falls. The Glenwood Canyon walls are steep, Hunter said.

Many of the roots and vegetation that anchored rocks and dirt have disappeared. So a canyon that was susceptible to rock falls events even before the fire is even riper now.

“This canyon is very susceptible to rock fall,” Hunter said.

Damage to the guardrail is seen after boulders fell from the cliffs on Glenwood Canyon due to the Grizzly Creek Fire that started on Interstate 70 at MM 120 Aug. 10, 2020.
Chelsea Self / Glenwood Springs Post Independent

Several steps have already been taken to try to gauge the risks and provide tools to warn about threats to Interstate 70, utilities in the Colorado River corridor and homes in populated parts of the canyon.

Numerous rain gauges were installed high up the canyon walls to help foresee flash flooding potential. The U.S. Geological Survey has run hydrologic modeling and runoff for major drainages within the burn area. (The website wasn’t operating properly Friday.) The U.S. Service assessed areas where culverts need to be cleared, repaired and even enlarged to handle expected debris flows.

“Post-fire BAER implementation started late last fall and will continue this summer,” said Elizabeth Roberts, ecologist and BAER team coordinator for the White River National Forest. “We are doing emergency repairs on all recreation trails and roads within the canyon.”

At this point, the Forest Service does not plan to reseed significant acreage within the burn area. One hurdle is the terrain itself. Sending hand crews up the steep slopes is not practical or safe and it would be difficult to seed by airplane.

A slurry line wraps around billowing smoke from the Grizzly Creek Fire on Monday, August 24, 2020. (Kelsey Brunner/The Aspen Times)

“We have to have access and access in that canyon is challenging,” Roberts said.

Where access isn’t as big of a challenge, the Forest Service will monitor conditions to determine if terrain can be managed for natural recovery. In other areas, such as the interstate right-of-way and at trailheads, the Forest Service is working on reseeding with the Colorado Department of Transportation.

Specific areas will be targeted for recovery.

“Fire suppression lines need help,” Roberts said.

Places where firebreaks were cut by bulldozers or hand crews, for example, need soil amendments at the least to help natural vegetation grow back. Some of those areas may also need to be seeded.

The Forest Service has also secured funding for trail and road stabilization. Some of the work started last fall and will continue when the snow melts out.

White River National Forest spokesman David Boyd said the agency’s tentative plan is to open trails in the canyon, including the popular Hanging Lake, on May 1. Details will be released in March.

The Grizzly Creek and Shoshone rest areas remain closed. The Forest Service wants to coordinate the opening of the trails with those amenities.

A group called the Glenwood Canyon Restoration Alliance has been created to help with the ongoing healing effort.

The Colorado River divides Glenwood Canyon slurry and a burn scar on the ridge from the Grizzly Creek Fire on Monday, August 24, 2020. (Kelsey Brunner/The Aspen Times)

Hunter told an audience of about 50 people on the Roaring Fork Conservancy video conference that a lot of what unfolds in the Grizzly Creek burn area will depend on weather this summer and other the next three to five years.

The Lake Christine Fire affected Basalt Mountain and surrounding terrain in July 2018. The following August, a localized rainstorm dumped about eight-tenths of an inch of rain on the front side of Basalt Mountain in just 60 minutes, Hunter said. It resulted in mud and debris slides in the upper reaches of the town. The storm didn’t affect the areas with the highest burn severity.

“So we kind of dodged it,” he said.

Christina Medved, director of community outreach for Roaring Fork Conservancy, noted the paradox facing the Grizzly Creek burn area.

“We really need rain because we’re in a drought, but what’s going to happen (if it rains)?” she asked.


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