Eradicating Milfoil Protects Elwha Restoration Progress

While monitoring the Elwha River estuary the past few years following dam removal, the Lower Elwha Klallam Tribe has been keeping an eye out for invasive plant species, including the aggressive Eurasian water milfoil.

Milfoil is a dense plant that provides poor habitat for fish, birds and wildlife, grows quickly, displaces native plants, and decreases water quality for fish, said Kim Williams, the tribe’s revegetation program supervisor.

“There is a known population of milfoil in Lake Sutherland, which is connected to the Elwha River via Indian Creek,” Williams said. “Now we have found it in the freshwater pools in the Elwha estuary. 

“It’s such a special estuary, we want to treat it right, especially for milfoil,” she said. “It’s a horrible invasive plant that needs eradicating. It’s one of the worst weeds out there and a major destroyer of fish habitat.”

The tribe is implementing a rapid response “search and destroy” sweep of milfoil in the estuary, nearby Bosco Creek and the Elwha River mainstem. Removal treatments include the use of an EPA-approved herbicide and removal by hand. 

The tribe also will conduct outreach efforts to educate tribal members and the community about the dangers of spreading milfoil while working in the estuary, including making sure to clean their boots and waders after field work.

During dam removal from 2011-2014, 24 million cubic meters of sediment flowed downriver, resulting in 88 new acres of land at the river mouth, changing the estuary conditions from a saltwater/freshwater mix to a mostly freshwater system, Williams said. Milfoil proliferated during this change.

The effort to survey and eradicate milfoil will benefit the species that rely on the estuary, including chinook, chum, coho, sockeye and pink salmon, plus steelhead, bull trout and Pacific lamprey. The estuary is important habitat for these species to rest, feed and hide from predators as they migrate to and from the ocean as adults and juveniles.

The work was paid for a state Department of Ecology invasive aquatic plants grant.

Washington Conservation Corps (WCC) crew member Calvin Stokes, left, Kim Williams, Lower Elwha Klallam Tribe revegetation program supervisor, and WCC crew member Mike Hathaway survey for milfoil in the Elwha River estuary. Photo: Tiffany Royal