A popular horse trail into the Bob Marshall Wilderness Area is temporarily impassable for stock due to sediment flows that turned the Blackfoot and Clark Fork rivers into chocolate milk this week.
Heavy rains Sunday and Monday caused increased runoff into area streams and the washout of Monture Trail 27 in the Seeley Lake Ranger District this week, the Lolo National Forest announced Friday. While still usable by hikers, about 4.3 miles up the trail at the Yellowjacket drainage is impassable to stock due to increased flows that included debris.
Officials recommend that day-riders use the flat trail section before Bill Creek to turn around before reaching the blind corner before the Yellowjacket drainage, which is narrow and on a steep, exposed mountainside.
Monture Trail 27 is one of the main routes for horses entering the Bob Marshall Wilderness Area.
Quinn Carver, the district ranger, said they haven’t pinpointed any large, single source of the sediment that turned the Blackfoot River chocolate brown on Monday from Monture Creek. By Wednesday, the sediment flow reached the Clark Fork River, and that also became murky through Thursday. The worst appeared to have passed by Friday, although the Clark Fork remained thick with sediment.
“Although the creeks in the Monture drainage are intermittently running cloudy and likely contributing to the recent discoloration of the Blackfoot, we don’t believe it is the sole source of the discoloration,” Carver said in a press release. “We are asking that folks remain vigilant as they enter the backcountry and burned areas during hunting season, especially ahead of or right after weather events.”
Alternate stock routes for accessing the Bob Marshall Wilderness include Pyramid Pass Trail 416, Lodgepole Creek Trail 13, Hobnail Tom Trail 32, and Dry Fork Trail 31. Riders, stock and hikers are still able to access Falls Creek Trail 16 via the Monture Trailhead.
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Crews are heading into the site on Monday to try to make the Monture Trail passable to stock again, and expect that will take a few days.
The Monture drainage is within the area burned by the 2017 Rice Ridge fire, and the Yellowjacket area burned particularly hot, creating conditions that make it susceptible to debris flows. A “Burned Area Emergency Response” (BAER) analysis that was conducted after the fire showed it would be vulnerable when hit by major precipitation, and the Forest Service said the public should expect similar events in the future.
The National Weather Service in Missoula reported that the Swan Lake area experienced more than 3 inches of rain during a 24-hour period between Sunday and Monday afternoons. During that time frame, Seeley Lake experienced 1.85 inches of rainfall.
The area experienced a similar debris flow in July after a similar storm.
Monture Creek is a spawning site for bull trout, which are listed under the Endangered Species Act as threatened. They spawn in early to mid-September, and crews from Montana Fish, Wildlife and Parks expect to check for redds along what typically are gravel shorelines in the area after Sept. 21. FWP previously expressed concerns that the sediments could smother the eggs, but added that the fine-grained glacial soils also can provide additional insects to feed the fish.
The forecast is calling for sunshine and highs in the 70s and 80s for the weekend. By Tuesday, temperatures will be back in the 60s, with a slight chance of showers every day.
For more information on trail conditions in the Seeley Lake Ranger District, call 406-677-2233.