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Colorado River took a blow from I-70 landslides

A large mudslide from Blue Gulch shoved the Colorado River to one side and sent trees, limbs, shrubs and silt downstream toward Glenwood Springs and other river towns, at the same time it blocked Interstate 70. The river’s early attempts to repair itself are seen on Friday, August 13, 2021, near Glenwood Springs.
Wildlife crews and water quality experts struggle to even assess the damage, as emergency management officials warn of threats to the western lifeline for years to come.

When a mud and rock slide buried one of the more important highways in the West on July 29, the dramatic gridlock became a statewide spectator sport.

That same historic rock slide, at the same moment, blocked off the most important river in the West.

After decades of fierce arguments over damming up more of the water that rightfully belongs in the Colorado River, nature built a new dam in 5 minutes.

What happened to the fish? What happened to the river channel? What happened to drinking water downstream? Where did all the rafters go?

Collective emoji shrug?

It’s been a challenge getting any definitive answers to the temporary mud slaughter of the Colorado, as state disaster and highway officials rushed to open up I-70 as quickly as possible to restore commerce, tourism, and the Western Slope way of life. But now that a lane of the highway in each direction is open, and asphalt spreaders are on the job, some are turning their attention to the river that cut the canyon in the first place, and provides water and energy to seven states.

The relative silence about the river itself stems in part from immediate questions of who is in charge. For the highway, it’s CDOT. For the river, from the federal side, at least three different branch offices of the U.S. Army Corps of Engineers have a say in any fixes, said emergency services director Mike Willis.

“Albuquerque, Sacramento and Omaha, just for a few miles’ stretch of the river,” Willis said,of the Army Corps involvement. Others who need to be consulted on any river rehab include the U.S. Forest Service, the Colorado Parks and Wildlife, the Colorado Water Conservation Board, and many more.

Sorting out changes to the river could take years, not just months, Willis said. The debris, from rockslides made worse by wildfires that burned up binding vegetation, blocked the Colorado River channel completely at Blue Gulch before the relentless river cut its way through the pile within minutes.

“The channel has changed now in several places. And so we have to be thoughtful about it, do we put the river back in its original channel or live with the channel as it is, and mitigate and protect the critical infrastructure downstream,” Willis said.

A large mudslide from inside Blue Gulch spilled onto the Colorado River at mile post 123.5 on Friday, August 13, 2021, near Glenwood Springs. (Hugh Carey, The Colorado Sun)

One of the first problems, Willis noted, is that the altered river flow may endanger the all-important highway. The changing channel has pushed debris up against the canyon’s complex bridge structures and overhangs, and the continual push of the water could undermine the road.

“In fact, the CDOT engineers have identified some areas where that is the case,” Willis said. “And so we need to assess that carefully and in those instances, we probably will push the river back to its original flow.”

Willis compared the project to rebuilding the highways from Estes Park to the Front Range after the 2013 floods tore up the roads down the river canyons. The first goal of state crews then was to restore a basic road service, then redesign, strengthen and rebuild the roadway over years. But in that case, Willis said, they didn’t have to fix the river itself, because the channel hadn’t changed.

As for wildlife recovery efforts in Glenwood Canyon, Willis said, the multi-agency task force dealing with the Colorado River has not given Parks and Wildlife full access in the slide area to start making detailed assessments.

“Frankly, we haven’t gotten the canyon quite safe enough to turn them loose in there yet,” he said.

Though impacts on the river are significant, the Colorado River District, which handles policy and planning for the lifeline stream, had warnings the slides were coming, spokeswoman Lindsay DeFrates said. The district has teamed with the U.S. Geological Survey to place rain sensors in the wildfire burn scars inundated by the downpours and slides.

“These types of slides were a possibility based on the soil burn depth,” DeFrates said. However this year’s landslides get cleared, she added, the wildfire fallout will impact the Colorado for years to come.

“I think it’s going to be different every summer for a while,” she said. “I think we’re going to continue to see activity in this area over the next few freezing and melt cycles, and monsoon seasons.”

Parks and Wildlife northwest division manager Matt Yamashita said biologists were still gathering information about the slide’s impact and waiting for full access to the river bed. But he’s concerned about mud smothering food and breeding spots for Colorado River species for miles downstream.

Bill Dvorak, who runs river expeditions on multiple Colorado rivers, said those wildlife concerns are spot-on given his other recent trips on the Western Slope.

“I fished the Gunnison Gorge and we just had a big blowout on one of the side canyons,” Dvorak said. “It put so much silt and sediment into the river that almost all the big fish from there down died, because they couldn’t oxygenate. There’s so much silt in them. So I’m guessing the same thing would probably happen over on the Colorado.

“There’s going to be silt and sediment that settles onto all the rocks and boulders so that all of the aquatic species and insects aren’t going to be able to hatch. As far as fishing and vertebrates, I think it’s a disaster.”

The Colorado and its tributaries are also vital resources for humans living along the riverbanks, long before the waterway delivers farm water to Arizona or drinking water to Los Angeles. Glenwood Springs takes its drinking water out of Grizzly Creek and No Name Creek before they hit the Colorado, and sometimes from the Roaring Fork River, if necessary, city public information officer Bryana Starbuck said.

“All of our water source intakes are below burn scars (Grizzly Creek fire and Lake Christine fire) which means that the landscape is very sensitive to heavy rainfall, which causes these debris flows or high sediment-transport incidents,” Starbuck said in an email response to questions. “Given the nature of burn scars, stabilization of the land will take time and impacts will continue to develop.”

Water is always safe for drinking by the time it leaves the city treatment plan, Starbuck said, but the debris did force the plant to slow down and sometimes stop production altogether to account for mud, splintered wood and other flow.

“Glenwood Springs had to enact watering restrictions for outdoor watering (no lawn watering, filling pools, washing cars) on July 31 through August 4,” Starbuck said. The treatment plant did turn off flow for nine hours one night when too much debris threatened quality.

Just as highway engineers in the canyon are looking uphill to design ways to keep future slides off the highway, Willis said, naturalists will have to work with them to think of ways to keep new slides from cutting off the river itself for years to come.

“We do not feel like this is a one time deal,” Willis said. “It’s not a one and done.”