Climate Change and the Chehalis River: Experts Outline Potential Dangers for Fish and Flooding

Headwaters to Harbor:Groups Work to Monitor, Mitigate Against Changes


Editor’s Note: This story is part of "Headwaters to Harbor," a project by The Chronicle to document the Chehalis River from Pe Ell to Grays Harbor while highlighting people and issues connected to the river along the way. Our coverage is compiled at

For the Chehalis River Basin, models show that over time, climate change is highly likely to alter the landscape as communities know it today.

In reports sent to The Chronicle by the Grays Harbor Conservation District and the Office of the Chehalis Basin, models show warmer temperatures, longer dry seasons and more floods.

Mara Zimmerman, executive director of the Coast Salmon Partnership and Foundation, summarized the effects on the Chehalis Basin in the same three categories.

These impacts combined would amplify perhaps the biggest issue in the Chehalis Basin: there is too much water for part of the year, and not enough for the rest.

With warmer water temperatures, salmon would have fewer places to spawn and survive. In longer and hotter dry seasons, junior water rights holders would have their rights curtailed more regularly, resulting in shorter irrigation seasons and other economic repercussions. With more rain in the winter, catastrophic flooding is predicted to become more frequent and damaging.

All in all, climate change is a threat to assets of the Chehalis Tribe, farmers, fishermen, flood victims, loggers and environmentalists alike.

“Things are changing rapidly in the rivers and in the ocean. And there's nothing really we do here that can control the ocean. But I think it's important to have that in mind because for salmon, the ocean and the river are affecting their survival,” Zimmerman said. “For people (in the Chehalis River Basin) the rivers are really the key piece because it’s the rivers that are interacting with their lives.”


Fish and Flood

When Gov. Christine Gregoire appointed members to the Chehalis Basin Work Group in the 2010s (which later morphed into the Chehalis Basin Board), it was recommended the group work to reduce flood damages and restore aquatic species habitat in the near-term while considering long-term strategies to tackle flood damage and improve aquatic habitat.

In simplified terms, conversations between major entities along the Chehalis River tend to fall in two categories: fish and flood.

If no mitigation was taking place, climate change models show fish populations dropping and floods getting worse.

The most major recorded floods on the Chehalis River happened in just the last 35 years, in 1990, 1996, 2007, 2009 and 2022.

“Using these revised future climate conditions projections, a catastrophic flood is now estimated to occur at a 10-year to 50-year recurrence interval,” stated one Chehalis Basin Strategy memo.

While explaining climate models is not her area of expertise, Zimmerman pointed to the Newaukum as a clear example of change in the last few decades.

“Peak flows have increased (on the Newaukum River) over time for the last 50 years. And it's a real clear pattern. This is change. And I want to point to data sets we have that show change already happening to say, ‘Look, whether or not you think this predicted trajectory is going to happen going forward to the future or not, this change has happened,’” Zimmerman said. “And we need to think about what that means and how there are things we can do.”

In “Chehalis: A Watershed Moment,” a documentary about the basin and its fight against flooding and declining fish populations, former Lewis County Commissioner Edna Fund said, referring to the flood of 2007, “When we think about global warming, and other issues that are in front of us, we’ve got to do something. We just cannot let this happen again.”

The Chehalis River Basin is also the last in the state to have no salmon species listed as endangered under federal law, but the fish populations are still severely depleted, especially spring Chinook runs. As per the memo, spring Chinook populations in the basin are currently about 23% of historic run sizes.

Zimmerman said higher temperatures and longer dry seasons shrink habitat. And less habitat means fewer fish.

Anthony Waldrop, director of the Grays Harbor Conservation District, said sea level rise will also impact the river ecosystems negatively, and not just for salmon.

“The prediction over many decades is that high tides will get higher and higher upstream,” Waldrop said. “In the long term, it could dramatically change the landscape.”

In a 2015 report by Wild Fish Conservancy Northwest sent to The Chronicle by Waldrop, sea level rise predictions showed significant intrusion of saltwater upriver having the potential to kill most of the salt-intolerant tree species in the forest, destabilizing banks through the action of flooding and tidal surges.

More saltwater farther upstream also would damage coho salmon, which seek refuge there in the winter, according to the report.


‘Working for Everybody’

These models are based, as was stated earlier, on a world without mitigation and projects to improve habitat decline and flood damage. The real Chehalis River Basin has people dedicating their entire careers to combating these issues from miles above Pe Ell all the way to the Pacific Ocean.

That’s where Zimmerman rests her head.

“I have a lot of faith in people to solve problems. I really think that we have a lot of really dedicated minds and people who are thinking about the issues in the basin now,” she said. “Those solutions are found when you have people coming together with different understandings and different viewpoints. And I think that is also happening in the Chehalis Basin. The issues related to flooding are complex. They’re not solved by one viewpoint alone. They’re solved by people understanding how this affects the entirety of the community.”

Planting trees allows for more stable river banks, more share and therefore cooler waters. The Chehalis Basin Land Trust and the Lewis County and Grays Harbor Conservation Districts all work with members of the public to plant trees along the river throughout the year.

Large wood jams in the river cause scouring in the riverbed, which gives salmon more places to breed and lay eggs. Current-day river bank stabilization projects, such as one off Newaukum Valley Road, use innovative techniques to both avoid erosion of the banks while catching more wood to create jams. Creative projects like this — for which the Lewis County Public Works Department won a project of the year award — can protect both human interests and salmon simultaneously.

Farmers have adapted to floods with critter pads, giving livestock high ground during winter storms. People have lofted homes and regulations on building in the floodplain have become more stringent.

“Those are solutions, I think, that we are finding that are sort of working for everybody. And that’s a big deal,” Zimmerman said.

With so many folks in the Pacific Northwest whose livelihoods are tied to natural resources, such as loggers, fishermen and farmers, she said convincing them the problem exists or that people should be good stewards of the Earth is not the biggest issue. Likewise, the Chehalis Tribe doesn’t need convincing that climate change is affecting salmon populations so intertwined with its culture, because they’ve seen it firsthand, she said.

The tougher thing to tackle, Zimmerman said, is how many people, both in projects related to the Chehalis River and members of the general public, react to the topic of climate change by imagining overhanging clouds of doom.

She, instead, tries to see the opportunities.

“If we start the conversation by talking about what we have to give up, you kind of lost the conversation, right? But, if you start a conversation by thinking about what we have to gain.

“… That’s where we start to meet minds,” Zimmerman said.