Gravel beach plan aims to mitigate shoreline erosion on Flathead Lake

State parks officials are fast-tracking plans to install more gravel beaches around Flathead Lake as part of ongoing efforts to combat shoreline erosion.

Pebbled beaches are the norm for much of Flathead Lake’s natural shoreline, but a combination of high summer water levels and frequent storms have cut much of the lakeshore into a jigsaw of steep banks and exposed roots. Now, Montana Fish, Wildlife and Parks is seeking preemptive approval to recreate natural shoreline conditions at over a dozen parcels of state-managed land. 

About 3.5 miles of Flathead Lake’s shoreline have already been converted using what officials call a “dynamic gravel beach” design. Cobble, ranging in size from pea-sized gravel to 6-inch rocks, is spread across the shore at the lake’s high-water line. Unlike storm walls and riprap, the gravel moves as waves roll into shore, absorbing the water’s energy and motion. 

“It doesn’t deflect that energy further down the shoreline,” explained Flathead Lake District Recreation Manager Amy Grout. “The energy just fizzles out along those beaches.” 

The state agency has created a draft environmental assessment examining the potential installation of dynamic gravel beaches the goal of stopping the loss of existing shoreline, providing a natural transition from the water to the vegetative areas along the shoreline and improving recreation opportunities along the shore of the lake. Public comment is being taken on the project.  

Grout oversaw the recent installation of a gravel beach at the Yellow Bay Unit of Flathead Lake State Park. After decades of wave action, the park had lost so much land to shoreline erosion that infrastructure like benches and campgrounds were being threatened. The shoreline was creeping closer and closer to the parking lot, and a nearby resident told Grout he was forced to reroute his driveway after decades of waves dragged some 10 to 15 feet of shoreline underwater. 

In March and April 2024, the state agency replaced about 1 acre of battered shoreline with cobble from Woods Bay Gravel. Technicians used backhoes to rake the gravel into a pattern that distorts wave action and minimizes erosion.  

Grout said the project was a “really huge success.” The new beach minimized soil erosion in the coming summer months and created more space for recreationists to enjoy the lake. 

The success of the Yellow Bay gravel beach, as well as previous projects at Somers Beach and Finley Point, inspired the agency to undertake a lake-wide dynamic gravel beach proposal. The document fulfills the environmental assessment requirements for any future gravel beach projects, so officials can immediately begin the planning and construction process once a new project site is identified. 

“This is working really well on Flathead Lake, so, as funding and needs arise, this is our preferred method,” said Grout. 

In the proposal, state officials said the Big Arm, Wayfarers and West Shore units of Flathead Lake State Park would all benefit from dynamic gravel beaches, but the agency’s next priority is Woods Bay Fishing Access Site. Cut banks as high as 4 feet already crisscross the shore, and officials say the area could lose more land and vegetation if action isn’t taken. 

“We’ve got some time. We’ve got some linear feet,” said Grout. “But it’s there.” 

Funding for a project at Woods Bay Fishing Access Site has not been secured. If plans do move forward, Grout said the construction would occur in March and April, when the lake’s water levels are at the lowest and recreation is minimal. During past gravel beach projects, boat ramps and other infrastructure remained open for public use.  

Other state lands listed in the proposal, including several wildlife management areas and fishing access sites, are not in immediate danger from shoreline erosion. While it is unlikely the agency would construct gravel beaches at these locations, Grout said their inclusion in the proposal would allow the state to reevaluate changing conditions and implement a quick solution if problems do arise. Some sites, such as Wild Horse Island, would likely be cost prohibitive, even if shoreline erosion worsens. 

The bottom line, said Grout, is that gravel beaches are the best tool managers have to combat shoreline erosion on Flathead Lake. If the proposal is approved, it would be one step closer to a “living shoreline solution to the erosion problem.” 

Montana Fish, Wildlife and Parks is accepting public comments on the proposal through March 13. Comments may be submitted to Amy Grout at agrout@mt.gov.