GRAND COUNTY, Colo. (KDVR) — After recent spring storms across the Front Range, experts are on high alert for triggered landslides.

Northbound Highway 125 between Trail Creek and Forest Service Road 112 in Grand County reopened on Friday after a mudslide spilled into the road. 

Francis Rengers, a research geologist with the U.S. Geological Survey Landslide Hazards Program, said landslides are more common in Colorado come springtime.

“Precipitation is the primary driver, so that’s what we are always looking at,” Rengers said. “If we have a long steady rain, we might have soil getting saturated and that’s what creates a landslide.”

He used the analogy of a ball pit that children play in to better describe the impact of rain on soil. 

“In the ball pit, there’s air and space in between those, so if you imagine that’s what soil is, that starts to fill up the space in between the balls. Eventually, if you get enough water in there, the balls are no longer touching. They’re now floating, and if you have material that’s not in contact on a slope, that’s what tends to trigger a landslide,” Rengers said. 

These phenomena are most likely to happen in mountainous areas.

“There’s sort of this sweet spot starting at the base of the foothills and steep areas going up to 8,000 to 9,000 feet,” Rengers said.

Colorado high country on alert for mudslides

Areas like Glenwood Canyon are no strangers to debris flows. In 2021, the Colorado Department of Transportation closed Interstate 70 for several days because of a massive debris flow. 

“You have rapid runoff into channels and those channels have material that then fails together, so this is what we saw in Glenwood Canyon,” Rengers said. “We saw debris flows triggered by monsoons.”

This season, Rengers said they’re keeping an eye on the burn areas and watching for lengthy spring storms.

“If we have a concern that there may be a landslide problem, we relay that to the National Weather Service, and they will offer watches and warning and they coordinate with CDOT to come up with rainfall thresholds,” Rengers said.

When it comes to snowmelt, Rengers said it usually doesn’t melt fast enough to trigger anything. But once the rain comes, it’s a different story.  

“When it melts, it does saturate the soil, and then you might have a rainstorm that comes on after that,” Rengers said. “You have this pre-saturated area and then it’s ready to go.” 

Rengers recommends checking before heading out, especially if you’re traveling through the mountains.