Glenwood Canyon Mudslides: Even Rainfall Events That 'Aren't Extreme' Will Lead To I-70 Closures
(CBS4) - With one rain event after the next, it's likely going to be a long summer for those who rely on Glenwood Canyon. On Monday, less than 24 hours after Colorado Department of Transportation cleared the canyon from Saturday's debris flows, Interstate 70 in the canyon closed once again for about an hour.
"If we get more than about .3 inches of rainfall in 15 minutes or more than about a half inch of rainfall in 30 minutes, we have a chance for a debris flow in that area and that actually lines up with what we've seen from the recent rainfall," said Francis Rengers, a research geologist at the U.S. Geological Survey. "Unfortunately they aren't extreme events, those are pretty common rainfall events that we get in the summer here but that's enough to cause debris to come down onto the road."
With a snow avalanche, the areas they occur in typically become more stable after a slide. That is not the case with these burn scar debris flows.
"There's unfortunately a lot of soil on those hills that can still move. I wouldn't say that if it happens once then we're good to go. We can't really let our guard down this summer because there's still quite a bit of soil and sediment that can be recruited to move around in those debris flows," he said.
There were a total of five different mudslides in the canyon over the weekend. Fortunately, drivers who were stuck made it out safely. Monday, with the threat of more rain, CDOT wasn't taking any chances and closed the interstate.
While CDOT is working closely with the National Oceanic and Atmospheric Administration to try and predict when closures may need to happen, it isn't easy.
"Sometimes they'll have one little weather cell go over to a spot that wasn't expected and then it drops a bunch of rain and then we have a mudslide there, so really pinpointing the accuracy of these smaller cells is challenging and NOAA is staying on top of it as much as they can and letting us know anytime they have new information about that," said Elise Thatcher, Communications Manager for CDOT's Northwest Region.
Despite the difficulties in predicting the weather, the agencies involved aren't taking chances.
"It's not worth losing your patience and getting too mad if you're waiting in traffic because they close the road because it could be a lifesaving thing if they close the road," said Rengers.
Rengers said it will likely take several summers before there is enough regrowth to hold the soil on the canyonsides in place once again.
"These things can actually last a while and the next couple years, we still have to be careful, this summer is probably going to be our worst summer for Glenwood Canyon," said Rengers.
