It’s not your imagination.
A landslide in one of the Hoback River’s main tributaries has sent a flush of sediment downstream, inducing a red-orange sludge that has temporarily tarnished its more typical blue hue.
The slide is thought to have taken place on Wednesday just upstream of the Granite Hot Springs Pool before flowing down Granite Creek into the Hoback, an area popular among river runners.
Todd Stiles, the Bridger-Teton National Forest’s Jackson district ranger, said it’s not unusual. But he hasn’t before seen the confluence of a chalky red Granite Creek and Hoback River.
“I’m sure it won’t be the last [time],” he said.
The slide likely started on the ridge of Open Door Mountain, Stiles said. Parts of a nearby trail are covered in mud, but still accessible to hikers, Stiles said.
The Upper Hoback Basin drainage system often sees slides during peak runoff or periods of heavy rainfall. But last week’s slide barged through without either in the days leading up to the slide.
“I’m not sure why it happened right now because it definitely would have been more logical if we had some sort of large rain-on-snow event where we had a big pulse of water,” Stiles said. “It doesn’t really seem to coincide with anything like that.”
When Stiles went up to see for himself, he noticed the slide didn’t necessarily slow down kayakers. But excessive debris from the slide, like logs and mud, could make for extra river hazards, he said. The same goes for hikers, until trails are cleared.
This isn’t the first time a large slide event changed the color of the river: in 2018, a landslide temporarily closed Highway 191 through Hoback Canyon. In 2014, the Jackson Hole News & Guide documented a similarly red Hoback River flowing into the Snake River at the end of the canyon.
