The good news in the wake of the Bonneville Fire, which blackened the Wasatch foothills behind the University of Utah campus last month, is that the flames did not damage soils, dampening the potential for post-fire erosion.
The denuded hills, however, will remain at elevated risk of debris or mud flows for up to three years while vegetation recovers, according to an assessment prepared by the U.S. Forest Service known as a Burned Area Emergency Response, or BAER.
To contain the potential damage from such flows, university officials are placing Jersey barriers and sandbags along the Bonneville Shoreline Trail. With the approach of monsoon season, that action will reduce the chances of rain-entrained debris reaching the university's medical and research facilities immediately below the burned area.
The Bonneville fire was triggered June 20 by human activity and scorched 572 acres, or just under a square mile, over a few days. Quick action by firefighters prevented flames from spreading into a nearby neighborhood.
The burned area spans Mt. Van Cott, from the north side of Red Butte Canyon to the mouth of Dry Creek Canyon. Some 319 acres are on Uinta-Wasatch-Cache National Forest and the remaining 253 acres are private land.
The Bonneville Shoreline Trail skirts the burned area, which is a magnet for casual outdoor recreation close to campus. Of particular concern is the fire's location just above the university's busy medical facilities.
Mudflows off the burned hillside could disrupt much more than mountain bike access, hence the urgency of revegetating the burned ground and preventive measures.The BAER report does not include the assessment team's recommendations for vegetation recovery
None of the ground affected by the fire met the standard for "severe" Soil Burn Severity, and just 7% met the standard for "moderate" burn severity. That means for 93% of the burned area, the soil structure was left unchanged by the fire, although ebris flows remain a possibility, the report cautioned.
"The basins and stream segments have a 50% probability of triggering a debris flow in the first- year post-fire in response to a 15-minute rainfall intensity" of more than 32 millimeters (1.26 inches) an hour, which is the equivalent of a 2-year rain event, the report said. The south end of the burned area, the part facing Red Butte Canyon, has the lowest triggering threshold, meaning this is where debris flows are most likely.
"In subsequent years, it takes a greater storm intensity to trigger a debris flow due to recovery of vegetation and soils," the report said. "However, the burned areas and areas disturbed due to suppression activity creates conditions for invasive species to outcompete native plants and expand their infestation.
"It is important for the public to stay informed and prepared for potentially dramatic increased run-off events," the report continued. "Burned-area watersheds will likely be more responsive to rainfall and prone to erosion and sediment transport due to post-fire conditions. However, vegetation recovery is anticipated to be rapid with ground cover approaching pre-fire conditions within 1-3 years, which will attenuate any post-fire effects on watershed processes."
Banner image: Flames scorched 572 acres in the foothills above the University of Utah's health science campus on June 20, 2026. Photo credit: Dave Titensor
