Culvert inventory a new approach to widespread fish passage challenges

Beneath the network of roads that allow people to move across the landscape, fish access to habitat is often disrupted by poorly placed or undersized culverts.

The Tulalip Tribes’ Natural Resources Department is streamlining efforts to find and fix these human-made tunnels, to restore fish access to valuable habitat in the Snohomish and neighboring watersheds and give chinook, coho and chum salmon a better chance of survival. Central to the effort is a new and growing inventory of culverts, including their locations and conditions for fish.

“We are trying to help the fish,” said Natasha Coumou, a restoration ecologist for the Tulalip Tribes. “It will serve the tribal members because it is a resource they subsist on.”

This year, Tulalip began systematic field surveys of sites where roads and driveways intersect with fish-bearing streams on the Tulalip Reservation.

A survey of about 250 of those sites on reservation land began in May. With the help of a Washington Conservation Corps Environmental Justice pilot project, the survey is populating a digital database showing where culverts are located and what problems they present for fish. The database will help Tulalip prioritize future fish passage project sites and improve the odds of securing funding.

Adrienne Monroe, assistant supervisor of the Washington Conservation Corps Tulalip group, (right to left) and corps members Nathaniel Hauer and Aelfhild Wiklund collect measurements at a culvert on the Tulalip Tribes’ reservation in July.
Working with private landowners, Tulalip has slated this perched culvert and two others like it for replacement on a tributary creek to the Pilchuck River. Photo: Tulalip Tribes

Along with the on-reservation survey, Tulalip is coordinating with partners to expand the effort into outside areas along the Snohomish, Skykomish and Snoqualmie rivers and their tributary streams, as well as to the Stillaguamish and Pilchuck river systems. Coumou said about 1,000 culverts in the region are an immediate priority to address because of their locations low in the watersheds, where salmon spend significant time during migrations to and from the salt water. Thousands more will need to be assessed in the future.

As survey data becomes available, replacement projects will be prioritized in places where malfunctioning culverts impact treaty fish, as well as where they create problems for community members.

“There’s an impact to infrastructure and a diminished quality of life for residents when they are repeatedly flooded,” Coumou said. 

Before the streamlined inventory efforts began, Tulalip was already working on some culvert replacement projects to address fish passage and flood issues.

Sections of Coho Creek, for example, are often inaccessible to fish because of clogged culverts and flood low-lying areas of the reservation. Tulalip is preparing culvert replacement projects at a crossing beneath the major thoroughfare of 88th Street, as well as in a more rural setting downstream, where beaver activity routinely blocks an undersized culvert, flooding the road.

“To open the whole Coho Creek basin, we want to replace those culverts,” said Matt Pouley, Tulalip Tribes restoration biologist.

A clogged culvert is hidden beneath vegetation and nearly covered by the backfilled waters of Coho Creek in July.

In the broader Snohomish River basin, Tulalip is undertaking another series of culvert replacement projects in partnership with Snohomish County and the Snohomish Conservation District, using $9.7 million from NOAA’s Restoring Fish Passage Through Barrier Removal grant program. Those projects will restore fish access to 32 miles of habitat across several creeks while also mitigating flood risk for surrounding communities.

As the tribes’ growing culvert inventory brings to light more fish barriers on the landscape, Tulalip will be able to roll out more of these types of projects—a critical piece of the salmon recovery puzzle—more quickly.

Partnering with local government entities, nonprofits and landowners along the way is essential.

“It really takes a lot of people to move these projects forward,” Coumou said. “We are looking to see which culverts we need to go after, and then divide and conquer.”

At top: Washington Conservation Corps member Nathaniel Hauer measures the diameter and water depth in a culvert on the Tulalip Tribes’ reservation in July. Photos and story: Kimberly Cauvel