Back in 2021, things were much drier around here.
That summer, a four-day wildfire raged on the south side of I-80. And in its aftermath, a debris flow caused by a flash flood came within 75 feet of the highway.
At the time, wildfire response coordinators said the threat of flash floods could last for three to five years. So this year, emergency managers are paying close attention.
“Anytime you have a burn scar, you have a more susceptible area, there's no getting around that,” Summit County Emergency Manager Kathryn McMullin said. “That ground cooks at many thousands of degrees, and that reduces its ability to retain moisture.”
The burn scar in Parleys Canyon is between Parleys Summit and Lambs Canyon, at the beginning of the descent into Salt Lake Valley.
As McMullin said, the soil in that area could still be water-repellant. If rain or snowmelt saturates the debris on top of the water-repellant soil, a mudslide can form.
She said officials hope the scar is far enough from structures and the highway that any soil movement will be easily contained, but there are never any guarantees.
“We can be proactive, we can be careful, we can monitor closely,” McMullin said. “But a lot of it is going to have to be a great response: that's interagency coordination, equipment, community members’ participation.”
She said officials have been able to be proactive in the area. The Utah Department of Transportation is in charge where highways are concerned, and it has stationed equipment to respond quickly in the event of a slide.
How dangerous such a slide would be depends on how much debris is in the area. The National Weather Service distinguishes debris flows from mudslides and mudflows because they can include fallen trees, boulders and other large objects.
I-80 has already seen two mudslides this week, neither of which rose to that level of severity. Still, one in the early morning hours on Thursday caused two accidents and injured one person.
That slide occurred near Emigration Canyon, farther west of the burn scar. The other mudslide happened on Wednesday afternoon near Wanship and caused no damage, coating the highway with rubble small enough to drive over.
Both mudslides affected only the eastbound lanes.
