From The Fort Collins Coloradoan (Miles Blumhardt):
Two assessments conducted by Arapaho and Roosevelt National Forests officials offered a sobering look into the devastation the Cameron Peak Fire left on Larimer County’s landscape and recreational sites.
The Burned Area Emergency Response studies were released Dec. 17 as part of the initial fire recovery process.
While the Cameron Peak Fire had a fire perimeter that enclosed nearly 209,000 acres, the impacts on the landscape by the largest wildfire in Colorado history varied widely, ranging from swaths that went unscathed to areas that were severely burned.
The survey showed an estimated 36% of the area within the Cameron Peak Fire perimeter suffered high (6%) or moderate (30%) soil burn severity. That indicates an increased risk of erosion and flooding caused by the soil being less able to absorb moisture, along with a lack of vegetation to absorb water and roots to stabilize the soil…
Another 44% of the area suffered low burn severity and 20% was unburned.
The assessment said determining soil hydrophobicity, or the ability to repel water, was hampered by snowfall during the assessments. However, it estimated 55% of the burn area could contain water-repellant soil.
The assessment said there is a 90% to 100% chance that water quality would be impacted by post-fire ash and sediment-laden runoff, nutrient loading and potential debris flows within the first few years following the fire.
Options to reduce the impacts to stream flows, soil erosion and debris flows are limited due to the nature of the burn and slope characteristics, the assessment noted. It stated treatment recommendations should focus on minimizing life/safety threats and damage to property through road and trail closures, trail stabilization, campground treatments and warning signs.
Given all the recreational sites in or near the burn area, the assessment said the consequences for potential impacts on life and safety are “major.”
Where it burned hottest
Soil burn severity is the result of fire progression and intensity. The longer the fire remains in an area, the higher the likelihood of high and moderate soil burn impacts. Areas burned during large runs from the wind-driven fire generally suffered lower soil burn severities due to the fire moving more through the tree canopy than on the ground.
The assessment’s soil burn severity map shows the area around the starting point on the west side of the fire near Chambers Lake suffered high soil burn severities. Other high soil severity burn areas occurred north of the Colorado State University Mountain Campus east into the Buckhorn Road area and in the northern section of Rocky Mountain National Park.
The Thompson Zone of the East Troublesome Fire that burned over the Continental Divide to near Estes Park burned mostly in the low to moderate category.
Most of the fire’s rapid growth was driven by high winds usually preceding precipitation events, mostly snow. The map shows the area to the east of the fire’s initial starting point suffered low soil burn severities during such an event.