by Marissa Lorenz
In recent weeks, Interstate 70 through Glenwood Canyon has been closed on a regular basis, stranding hundreds one day last week and finally being shut down for an indeterminate period of time on Saturday, July 31, when the roadway sustained “extreme damage” following a rock/mud slide in the fire-damaged area.
Highway 125 north of Granby has been closed on and off for weeks, when heavy rains have brought fear of–or reality of–excessive water, silt, debris, and brush washing down the soil-damaged Willow Creek drainage.
Highway 14 northwest of Fort Collins has experienced closures due to flooding and mudslides. And Highway 24 near Manitou Springs has been the subject of closures and flash flood warnings over the past month.
All of these roadways are located within burn scar regions.
I-70 and Highways 125 and 14 are in areas burned, respectively, by the Grizzly Creek, East Troublesome, and Cameron Peak fires last year. Highway 24 runs through the Waldo Canyon burn scar, left by an 18,247-acre fire that destroyed 346 homes–in 2012. It is an example of how long the land can take to recover from fire, and the dangers that linger.
The East Troublesome Fire, which began near Corral Creek east of Kremmling, burned over 193,000 acres and destroyed 365 homes in October 2020. Having burnt over 100,000 acres in the single night between October 21 and 22, it is considered the fastest-growing wildfire ever recorded. And it left a large scar on the landscape of Grand County.
Fire recovery efforts have been ongoing since the fire, with new or redirected staffing, cleanup efforts that have brought volunteers from across the country, and an Emergency Watershed Protection (EWP) program that is “focused on watershed assessment, recovery, and early warning systems.”
But the best efforts will only mitigate the many possible environmental impacts to the area, and water, in the form of runoff or rain, is chief among the present concerns.
“There will be flooding,” cautions Carol Ekarius, a civil engineer and chief executive officer of Coalitions and Collaboratives, Inc. (COCO), a Colorado nonprofit founded in the aftermath of flooding after wildfire and which is partnering with Grand County in its recovery efforts.
“And there will be excess sediment and debris washing into the reservoirs, Lake Granby, and the Colorado and its tributaries in the areas below the scar. Exactly where, exactly how much, exactly when— these are unknown and the best crystal balls can’t provide answers, though the state and feds have provided some modeling analysis to help plan response efforts.”
The fire burned east from the east fork of the Troublesome so the most highly impacted areas will be outside of the Kremmling area. And Katherine Morris, Grand County Water Quality Specialist, indicates that “[f]looding concerns below the confluence of the Troublesome and the Colorado look to be lower than areas within or immediately below the burn scar, particularly those with large drainages upstream.”
However, she goes on to confirm that “[w]hat will likely affect the mainstem Troublesome would be sediment and debris flow.”
Mark Volt, retired District Conservationist and current contractor for the Soil Conservation District, notes that models show the greatest danger is in cases of cloudbursts, defined as sudden, extreme rainfall, usually of brief duration, but which can create flood conditions and which are a common occurrence in the high mountains.
Volt explains that a cloudburst with 2- to 3-inches of rain per hour is modeled as pushing 3,000 cubic feet per second (cfs) of water down the East Fork of the Troublesome and across the valley below, an event “no one has seen before.” He observes that, even with engineering to divert water from roadways and to save the bridge and the headgate of the Ennis Ditch, an irrigation canal which supplies water to many of the ranchers in the Troublesome Valley, County Road 2 will still act as a “spillway,” guiding water all the way down the valley.
Volt attests that that kind of rainfall is not very common–maybe a 10-year event, meaning it has a 1/10 chance of happening each year–but that it does happen. He points to a recent incident in which the town of Basalt, Colorado, located below the burn scar of the 2018 Lake Christine Fire, was flooded with silt after 1.5 inches of rain fell in an afternoon. And he recalls just such a cloudburst near
Kremmling in the early 1990s that “overpowered culverts” and flooded roads and fields.
“And if that happened with no vegetation!?” he exclaims, wondering at today’s post-fire conditions. “If it hits before the area is healed, there will be no vegetation to soak up the debris flows.”
“If we can have five years of slow, steady rain, and vegetation growth, when it rains, it won’t cause as much soil erosion,” Volt continues. “[The rain] will hit vegetative particles, and it will come off more slowly–but that’s five years, maybe up to 10 years, though five years seems to be a tipping point.”
Troublesome landowners indicate that they’re worried about potential flooding impacts but have little to do other than shore
up headgates, replace culverts, and clear brush and other rubbish from the waterways hoping to lessen debris buildup in case of a flood.
Rick Wahl, who recently moved lower on the Troublesome from the confluence, notes that with the minimal snowmelt this year,
he didn’t see the predicted trash, branches, boulders, et cetera during the early part of the season. But he says he’s expecting slurry and mud to cause blackwater in any monsoon-like conditions, which would negatively impact his fisheries.
Mike Ritschard, whose family were early settlers on the Troublesome, indicates that the headgate for the Ennis Ditch was replaced in the spring and that he had very little else to do but wait for the untenable quantities of water expected to arrive at some point.
In the meantime, road closures such as those seen in the past few weeks, may continue into the future, due to weather concerns and/or sediment wash-out. Homes, businesses, irrigation systems, and other infrastructure may suffer anything from minor damages to complete loss from flooding.
But “[t]he worst potential impact of post-fire flooding is lives lost,” reminds Ekarius, though she notes that the County and other partners, such as the National Weather Service, are actively working on warning systems. “If people heed those warnings, they should remain safe.”
She further recommends that anyone located in drainage ways purchase flood insurance and that they prepare “go kits”
and evacuation plans.
For more about fire and watershed recovery efforts in Grand County, go to https://www.co.grand.co.us/1355/Fire-and-Watershed-Recovery.
For more information on the threat of flood after fire, go to https://www. weather.gov/bou/floodafterfire.
To sign up for National Weather Service notifications, go to https://www.weather.gov/crp/wea.