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Mudslides, flooding and rockfalls highlight summer hazards to be aware of

A mudslide covers the Tenmile Recpath at mile marker 198 on Friday afternoon, July 23. The incident followed heavy rain in the area.
Photo from Summit County government

From Loveland Pass to Glenwood Canyon, it’s been a summer of mudslides triggered by heavy rain. A Colorado Department of Transportation representative said that in addition to mudslides and flooding, rockfalls and landslides are summer hazards that community members need to be prepared for.

On Friday, July 23, two mudslides triggered by heavy rains closed U.S. Highway 6 over Loveland Pass for nearly 48 hours. Bob Group, Geohazards Services manager for CDOT, said the pass is an area where the department has had issues before.

Group said on Wednesday, July 28, that in the past week there were as many as seven areas on Colorado’s highways that experienced mudslides that were not related to wildfire-burn scars. He said that in some of these areas, a mudslide happens every few years, but in other areas, they had no record of a mudslide ever occurring before.



Group explained what the department looks for when it comes to an area’s susceptibility for mudslides.

“(There are) a few different factors: it’s terrain, and on the terrain component there’s sediment that’s available for transport; there’s steepness of the drainage and then the shape of that drainage and how it intersects the highway,” Group said. “The other component is the rainfall component. So pretty much anywhere there is sediment available for transport, that steep drainage, if you get a high enough intensity rain event, can cause a mudslide or a flooding event.”



In Summit County, areas that could potentially slide are Loveland Pass, where there is a history of mudslides, and Hoosier Pass, which doesn’t have a history but is susceptible under the right conditions.

“Areas that we don’t really have a history (of mudslides), if they get a high-enough intensity event then you will get debris flows,” Group said.

When it comes to all weather events, Summit County Emergency Management Director Brian Bovaird advises residents to pay attention to any alerts that come out. Public safety alerts sent in the area come through peoples’ cellphones. Residents can also check Weather.gov for updates on hazardous weather conditions and can sign up for Summit County Alerts at SummitCountyCO.gov/scalert.

Unlike winter hazards, Group said there isn’t a lot travelers can do to be proactive about summer road hazards aside from being prepared to be stopped in their cars. He added that while debris flow and flooding have been frequent culprits of road closures this summer, CDOT typically deals with rockfalls and landslides.

As a general rule, Group advised motorists to avoid driving their car through moving water or flowing debris because it is difficult to know how deep the water is or will get further down the road.

“The mudslides and debris-flow events have a lot more energy in the flow, so it can move a vehicle a lot more easily than a clear-water flooding event would,” Group said. “It’s more likely to move your vehicle off the highway.”

Group said CDOT has been recommending that people don’t drive in burn-scar areas during rain events where there’s an elevated likelihood of mudslides and debris flows, such as Glenwood Canyon. But outside of burn areas, the department doesn’t usually advise people avoid certain areas because there is a low likelihood of hazards.

As for rockfalls and landslides, Group said these are more common in the spring and fall due to temperature fluctuations, but they can also happen in the summer as heavy rain or other high-intensity storms loosen rocks. He said people can protect themselves in these situations by trying not to be under an exposed rock face if stopped in a vehicle.

“We’re all in the same boat of dealing with the unpredictability of the weather,” Group said. “The same thing that we tell people anytime they’re going to go out on the highway is be prepared for stops; just be aware of what’s going on around you.”


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