Massive mudslides triggered by heavy rains are tearing apart heavily logged watersheds all over the Clearwater National Forest.
One slide is damming the Lochsa River, causing it to flow over U.S. Highway 12, which the Idaho Department of Transportation closed Thursday.
The Forest Service confirmed eight to 10 slides and expects to find more.
The largest is a pile of mud and debris that came off of a steep hillside about 20 miles east of Dworshak Reservoir on Quartz Creek.
It is an estimated 600 feet wide and 60 feet tall, littered with boulders the size of school buses. There is a lake about an acre in size behind the slide and water is spilling over the top.
“It’s still growing,” Doug Gochnour of the Clearwater National Forest said. Forest Service officials are having a difficult time surveying the slide “because there is constant rock fall,” he said.
The massive slide is located about 20 miles east of Dworshak Reservoir. “There is a chance we may never reopen (the Quartz Creek) road,” Gochnour said.
There hasn’t been enough logging near the Quartz Creek slide to cause the problem, the agency says. But not everyone agrees.
“They’ve been picking at that for years,” said Al Espinosa, who was the Clearwater National Forest fisheries biologist for two decades.
All of the slides are near roads. The smallest slides washed out half of the roads for 30-foot-long stretches. The largest, outside of Quartz Creek, involves the entire road slipping down the slope, said Ervin Brooks, a Forest Service engineer.
The Quartz Creek slide happened two weeks ago; the rest in the last two to three days.
Espinosa said he’s been warning of the problems since at least 1975. “Those watersheds have been hammered continually,” he said.
“Every year until I left (in 1993) I told them they should stay out and let those watersheds heal,” Espinosa said. “There’s no trees in the area to suck up the water.” And there are miles of road to slip down the slope in heavy rain, he said.
The slides may force the Forest Service to scale back plans to log the Clearwater, which is coveted by the North Idaho timber industry because of its extensive unlogged acreage, environmentalists say. More slides may soon occur in the Idaho Panhandle National Forest, they predict.
Charles Pezeshki, director of the Troy-based environmental group, Clearwater Biodiversity Project, calls it “a day of prophesy.”
“This is the day when all of the bad land-management practices across the state and national lands are coming home to roost,” Pezeshki said.
Calling the slides clear proof of the effect of heavy logging and road building on the landscape, he asked, “So what more evidence do people need?”
Forest Service officials say the intense rainfall, as much as 3 inches in the last 24 hours, is probably the main cause.
“I don’t think we have enough information to draw a large-scale conclusion,” Gochnour said.
“I know some of them are related to human activity, and some of them are related to rain and God,” he said.
Others who went out to look at the damage say logging and road building are the obvious culprits.
All along Highway 12, creeks that came from logged watersheds were also washing mud across the road, he said.
Forest Service teams will continue to survey the problems, the agency said. It will be days before the full extent of the damage is known.