After decades of collaboration between fish conservationists and agricultural interests, a 145-acre section of the Snoqualmie River, just downstream from Fall City, will begin a massive $17 million restoration this week, removing two flood-mitigation structures in an effort to improve spawning habitat for endangered salmon.

Once a highly-productive site for salmon spawning, the project site has seen a significant amount of habitat degradation over the last several decades because of modifications and developments that have altered the river and its natural processes.

Those modifications include the placement of the Barfuse Levy and Haffner Revetment, which sit almost parallel to each other along the river. Working in tandem, the two flood-reduction structures have sped up the river’s flow, disrupted natural processes and disconnected the river from its historic floodplain and side channels, contributing to a steep decline in spawning habitat for salmon populations.

“Where there seems to be a bottleneck in salmon recovery is the availability of places for juvenile salmon to grow up and rear,” said Ryan Lewis, a restoration program manager with the Snoqualmie Tribe. “They need areas out of the main channel where they can rest and hide from predators.”

To reverse course, King County is beginning work this week on the Fall City Floodplain Restoration project, which among other things, would remove portions of both flood structures. Doing so is anticipated to restore the river to a previous state, allowing reconnections with floodplain and side channels while also creating more bank erosion and slow-water pools.

A diverse and complex spawning habitat is created by a dynamic river, where banks can be morphed and degraded by the river and where trees can grow on the banks and fall in, said Matt Baerwalde, an environmental policy analyst for the Snoqualmie Tribe.

“That complex messy habitat is important for rearing fish,” he said. “In the Snoqualmie, we have a whole lot of steep armored banks. We find fish there, but it’s because they have nowhere else to go.”

The Snoqualmie River’s salmon spawning habitat is concentrated in two main stretches of the river. One of those spaces is below the Tolt River and the other below the Raging River, where the Fall City project is taking place.

“Those tributaries, the Raging and Tolt, are putting in the sediment that salmon need for successful spawning,” said Baerwalde, noting that a variety of sediment in the river helps produce a more diverse ecosystem.

Construction on the project is slated to take place over two summers to avoid restoration during the spawning or flood season. It began June 13 and will wrap up by September, before starting again next summer. Construction will not have road or river closures or impact Fall City Floating.

On the right side of the river bank, a 1,400-foot portion of the Haffner Revetment would be removed and a 3,100-foot-long side channel in the floodplain would be built. The project would also remove and set back a section of Neal Road that overlooks the river and build a new revetment.

On the left side, the 1,300-foot portion of the Barfuse Levy would be removed to restore 45-acre historic floodplain. In its place, a 2,000-foot berm would be built to provide necessary flood protection.

The Tribe and Oxbow Farm & Conservation Center will also work to remove noxious weeds and replant native plants and shrubs in the project area, Lewis said.

Although the project will benefit several species of fish — including Chum, Coho and Steelhead — its primary focus is on Chinook, which have been at-risk for decades.

Listed as endangered in 1999, Puget Sound Chinook are at less than 10% of their historic population levels, according to the county. That’s due to a variety of reasons, including habitat loss, rising water temperatures and fish passage barriers.

Drops in Chinook populations are of particular concern for the endangered southern resident killer whales, also known as orcas, whose diet primarily consists of Chinook. There are just 74 whales left, according to the Marine Mammal Commission.

Andrea Mojzack, the Snoqualmie Basin Steward for King County, said they can’t currently quantify how the project will affect Chinook populations, but noted that they are creating the best science-based effort to improve early salmon survival and will be monitoring the project site over the next decade.

“Removing bank hardening, creating slow-water habitat, re-establishing or improving the connectivity of water courses and floodplain areas, adding habitat-forming large wood — all of these things benefit juvenile salmon growth and survival,” she said.

Mojzack said the county can confidently say that 20-40% of Chinook in the entire river watershed spawn in the project site or at the nearby Raging River.

“There’s a lot of baby salmon in the region and we’re gonna see the biggest bang for our buck in terms of location in the Valley,” she said.

Fish Farm Flood

The Fall City project is significant not only for its size and location, but it’s also the first major effort to come out of the county’s Fish Farm Flood Committee.

Founded in 2013 by King County Executive Dow Constantine, the Snoqualmie Valley committee brought together representatives with interest in fish, farm and flood issues to define priorities and collaborate in balancing their often clashing interests.

For years, salmon advocates have made large scale projects a top priority to help restore salmon runs, Mojzack said. Due to its high-productivity as a spawning ground, a large-scale improvement near the Raging River had been in the works for over a decade.

At the same time, salmon advocates have had to balance those priorities against agriculture interests, which often have pushed back on some of those projects, Mojzack said, in order to prevent losing agricultural land.

Wayne Gullstad, president of the Snoqualmie Valley Preservation Alliance Board, owner of Cherry Creek Farm and committee member, said finding a balance between the needs of fish and agriculture is an incredible challenge because the two interests are often “diametrically opposed forces.”

“Ideally for fish there would be no development or agriculture,” he said. “The challenge has been coming up with a fair balance that provides important benefits to restoring fish habitat without unnecessarily harming agriculture.”

For the Fall City project, recognizing the high-value of the area for fish recovery, Gullstad said the committee’s agriculture group agreed to wider buffers in the project area than elsewhere in the Valley, noting that the fish group made a compelling science-based argument regarding the critical nature of the fish habitat.

“There is a great urgency in restoring fish habitat,” he said. “Working together, we can do great things, but that’s the key — we have to work together.”

In exchange for agreeing to the large-scale project, the farm group has been promised regulatory reform in areas such as drainage management, he said.

“The Fish Farm Flood project was an ostentatious idea for the county executive and county council to even suggest as a workable course of action,” he said. “But it has worked and it is working — it serves as a model for what can be done in other countries, statewide or even nationwide.”

Mojzack said agriculture groups weren’t thrilled that the project takes over former agricultural lands, but noted it’s a critical space in improving salmon runs.

“We feel like this is a fair ask for the Valley,” she said.

Correction: A previous version of this story reported that a side channel of 1,300 feet would be built on the right side of the river bank. The channel’s length was corrected to 3,100 feet. We regret the error.