Mudslides

After the deluge: An image of mitigation work, posted by the San Miguel Sheriff on Twitter, in the wake of mudslides that closed Bridal Veil Road and Trail and Imogene Pass earlier this week. (Photo courtesy of the San Miguel Sheriff)

Though recent thunderstorms to this region brought welcome rain, they also produced a new risk for drivers: the threat of mudslides. Look no further than Monday (if you can see past all the muck). On that afternoon last week, mudslides at Bridal Veil Falls were 35 feet wide, and 3-5 feet deep, according to an alert from the San Miguel Sheriff’s office on Twitter. 

“Bridal Veil Road and Trail and the Via Ferrata will be closed to ALL traffic through tomorrow due to mudslides” requiring mitigation work, the Tweet read. “It is not safe to be on the road or trails. Imogene Pass is currently closed and will reopen when safe to do so.”

The slides may have caught motorists and hikers off guard; but they were no surprise. Two summers ago, big rains produced mudslides in a place notorious for them, along Highway 145 near Sawpit. 

“There are certain areas that are known for producing mudslides,” National Weather Service meteorologist Dennis Phillips said. “Sawpit’s a big one. Red Mountain Pass, which gets more rockslides. And any place where there’s a burn scar from wildfire right near the highway, such as the one caused by the 416 Fire outside Durango. That’s a big one around here now.”

The trouble is, the weather service cannot predict mudslides. All it can forecast is rainfall.

 “We key in on rainfall rates,” Phillips explained, “where there’s a chance of a lot of precipitation in a short time. If we see a setup for a day that can produce heavy rainfall in a brief period,” the service will issue a warning about it (and did last week). 

“There’s no way we can predict that sort of scenario more than a week in advance,” Philips added (reporters are always asking him about long-term forecasts). 

“And it’s interesting you mention mudslides,” he went on. “Forty-four years ago today was the Big Thompson Flood,” a 70-minute-long deluge that caused the banks of the Big Thompson River (near Estes Park) to overflow, killing 144. 

“Sometimes storms form in the same spot, time after time,” owing to a unique combination of topography and winds aloft, Phillips said. “Mountains are notorious for focusing rainfall right into a specific basin.”

The result can be a place such as the stretch of Highway 145 between Placerville and Sawpit, which is locally famous for mudslides. CDOT has done much mitigation on this section of road involving drainage structures over the last two years —11 structures in the previous project, and 4 structures during the current one — which will help immensely when big rains come. But all that roadwork will neither turn off the spigot nor completely solve the problem.  

“We do everything we can to improve the roadways, from constructing new culverts to maintaining and clearing them of collected debris,” said Lisa Schwantes, CDOT’s Southwest Regional Communications Manager. “But when severe downpours occur, travelers need to be aware that flooding can still happen. We live in the Rockies. The weather Mother Nature brings makes these mountains rugged and ruthless at times. Be prepared!”

“Mudslides happen every year,” said Susan Lilly, the public information officer for the San Miguel Sheriff’s Office. “It’s part of living in the mountains. Be aware of the risks from heavy rain, and keep a lookout” at both the weather forecast, and local roads. 

CDOT advises motorists never to drive through any flooded area, given that it is impossible to know “how deep or fast the water is running.” (“Just 8-10 inches of water can float an average size car,” CDOT’s webpage points out, “which can be easily swept off the road.”) 

What’s more, water and mud can conceal rocks or debris, such as plant material or branches, beneath the surface. The best advice: “If you cannot see the roadway, be smart and wait for the water to subside.”

That’s why “it’s important to prepare for getting stranded,” Lilly said. “It’s not something you think about when it comes to summer driving, but you should keep extra supplies in your car: food, water and warm clothing,” just in case.