December floods test salmon habitats, restoration efforts

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2 weeks ago

Part 1 of a three-part series looks at recent local flooding events that made state history.

As experts are unsure of how impacted salmon populations are from the recent December flooding, salmon restoration projects are proving their importance. What could it mean for future flood mitigation efforts?

In December, Washington experienced large-scale flooding as multiple atmospheric rivers brought a historic amount of rainfall to the region. As rivers and streams overflowed, homes were damaged, people were displaced and animals sought shelter. For salmon, many of which had returned for the spawning season, there was no place to hide.

The impact of the flood on salmon won’t be seen until 2027–2029, when the eggs from this spawning season are expected to return, according to Mickey Agha, the statewide salmon science and policy analyst for the Washington Department of Fish and Wildlife, or WDFW.

“Systems like the Stillaguamish, Snohomish, Skagit and Nooksack may experience more detrimental effects over other watersheds, given the size and particular stocks that are spawning. However, it’s important to note that eggs being washed out doesn’t necessarily mean they are dead,” Agha wrote in an email. “Ultimately, some salmon populations are resilient.”

In 2021, flood waters impacted pink salmon spawning. During their return in 2023, according to Agha, strong survival was observed. Across the Salish Sea, pink salmon populations were higher than expected. For the Nooksack in 2023, the pink salmon forecast was 24,997 but what was observed was a population of 48,152.

The December flooding echoed the damage seen in salmon redds and fish habitat, while surpassing a previous river height record from 2021. In 2021, the Nooksack River crested at 149.6 feet. This December, it reached 150.49 feet.

Chinook salmon populations in the Nooksack forks are of particular concern, according to John Thompson, senior salmon recovery planner for the natural resources division of Whatcom County Public Works. Chinook salmon spawn from August to October. When flooding began in December, their eggs were washed away or buried under sediment, making survival less likely.

Thompson believes that the impacts for the species could be dramatic, but that the variation of their four-year return intervals, some salmon return at three or five years instead, could mitigate the impacts.

“We won’t really know until the spring,” Thompson said.

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Restoration leads to mitigation

In 1990, the Washington State Legislature established the Regional Fisheries Enhancement Groups to involve communities in salmon recovery efforts. There are 14 groups across Washington, each an independent nonprofit with its own board of directors. One part of this involvement is volunteer work, such as planting trees along riverbanks and learning about restoration efforts.

An NSEA project on Kendall Creek demonstrates the impact of restoration, with views before (2002) …

The Nooksack Salmon Enhancement Association — NSEA — is one of these groups dedicated to the recovery of salmon populations. NSEA works with landowners to remove fish passage barriers and to improve habitat for all fish, primarily salmon.

One of the main barriers removed is undersized culverts that get blocked, leaving salmon with nowhere to go. Salmon aren’t the only thing being blocked; water also has nowhere to go, causing the area to flood.

“Our main priorities really are working with landowners to remove barriers and then make sure the habitat is healthy,” Peck said. “Are there flood benefits included in that? Absolutely.”

Off the North Fork of the Nooksack, NSEA buried wood debris along the creek banks in September 2025. This helped create crucial habitat for salmon where they would be sheltered and have more spots to spawn. During the flooding in December, the wood debris did much more than help salmon.

“Where you could see just the top part of a root wad, you can see the whole thing now. It showed the power of flooding, of water,” Peck said. “But it also showed us that our work is doing its job. Where those large wood debris placements were, the bank is still intact, whereas it probably would’ve eroded away that whole corner.”

Moving upstream

Flood events and their impacts highlight the importance of restoring floodplains and estuaries, according to Agha. But restoration is not always possible everywhere due to human development, levees and dikes.

… and after (2008). Students from Kendall Elementary helped to plant the trees for the project. (NSEA)

Salmon are born in freshwater systems, go out to the ocean for several years and then return to their initial streams to spawn the next generation. A healthy habitat when they return is crucial to their survival.

According to Peck, water is meant to move and meander, but human activities such as logging and laying down impermeable surfaces like pavement have limited its natural movement. She said that the restoration projects NSEA has completed have helped mitigate flood damage and could be applied throughout the watershed.

“The river is going to grow and shift and flood,” Peck said. “I think what we can learn is that nature speaks to us, it’s a sounding board, this is its voice. It needs the ability to move and shift. What can we do to help accommodate that in a way that isn’t mimicking the last hundred years of management?”

WDFW will continue monitoring conditions to better understand the extent of the impacts on salmon populations. NSEA will continue to repair damaged restoration sites and work to support a thriving salmon habitat.

— By Margaret Baumgartner