Two environmental groups are taking the Flathead National Forest to task for a landslide that occurred below a forest road, shedding tons of debris into Sullivan Creek in the South Fork Flathead drainage.

Keith Hammer, chairman of the Swan View Coalition, and Arlene Montgomery, program director for Friends of the Wild Swan, recently wrote a letter about the landslide to the Flathead Forest and several state and federal wildlife and environmental protection agencies. The landslide was discovered and photographed on July 16.

An image from Google Earth indicates the landslide began sometime after July 25, 2013. It shows the landslide crack beginning to form just below the road. Flathead Forest officials believe the slide occurred sometime in the last few months.

A Flathead Forest report was prepared after an inspection in response to Hammer and Montgomery’s letter. The inspection found that the slide was roughly 250 feet wide and 150 feet long, with the base of the slide in the stream channel 300 feet wide and 150 feet long. 

Montgomery and Hammer assert that the slide occurred because of poor drainage of water from the slope above the road. Instead of draining through culverts, they said, water percolated beneath the road, destabilizing soils and causing the landslide.

“Sullivan Creek is the best bull-trout spawning stream in the South Fork Flathead outside of the wilderness. It consistently has the highest number of redds of the four Hungry Horse tributary streams that are sampled,” the letter states.

“We find this road-related landslide, the inappropriate location of the road, inadequate engineering of the road, ditch and culvert locations and subsequent inadequate maintenance to be an adverse modification of bull trout ‘critical habitat’ and a taking of bull trout in violation of the Endangered Species Act. It also degrades water quality in violation of the Clean Water Act.” 

However, the forest’s report, prepared by a hydrologist and engineering staff, contends the slide was caused by factors other than the road.

Sullivan Creek, it notes, has eroded a deep channel with steep slopes, and the entire drainage has been prone to slope failures that have occurred in other areas.

Spotted Bear District Ranger Deb Mucklow noted that similar slides occur along stream channels in the wilderness — where there are no roads.

The entire Sullivan Creek drainage was burned by a wildfire in 2003, worsening conditions for slides.

The report also notes that a mid-stream gravel bar caused Sullivan Creek to migrate toward the base of the slide area, causing persistent erosion.

“Therefore, the mass failure was most likely caused by the channel eroding the toe of the hillslope,” the report concluded.

To Hammer and Montgomery, the slide is relevant to the Flathead Forest’s approach to road management as outlined in a recently released draft Travel Analysis Report that recommends fewer road decommissioning efforts in the future.

Hammer says the forest should consider decommissioning more roads rather than simply keeping them in a state of low maintenance. He claims decommissioning would be more beneficial and cost-efficient in the long run.

Mucklow said steps will be taken to protect the Sullivan Creek Road from any erosion damage that might occur because of the landslide.

“Right now Sullivan Creek is used by a lot of hunters,” she said. “In the short term we’re going to work to assure that the access needed for the Sullivan Creek Basin” will be maintained.

Reporter Jim Mann may be reached at 758-4407 or by email at jmann@dailyinterlake.com.