McKenzie River Restoration Benefits Upper Willamette River Chinook

Image: National Oceanic and Atmospheric Admnistration.

NOAA’s Office of Habitat Conservation says the numbers of threatened Upper Willamette River Chinook salmon are increasing, thanks to habitat restored in Oregon’s McKenzie River watershed.

In 2022, NOAA provided $1.7 million to the McKenzie River Trust in congressionally-directed community project funds to restore 150 acres of floodplain habitat at Finn Rock Reach, an important habitat for Chinook salmon.

An update issued by NOAA Fisheries on June 3 said that adult Chinook spawned in restored habitat last fall, laying eggs in 65 “redds” – gravel nests they scour out of the river bottom. A new generation of juvenile Chinook is now growing there and will eventually head downstream toward the ocean, they said.

McKenzie River Trust Restoration Projects Manager John Trimble said the limited habitat prior to restoration confined salmon to a small single channel.

Workers used a cut and fill operation to reconnect the river to the floodplain, increasing the wetted area where water can flow across the site, and let the river do the work of rearranging sediment into preferred flow paths, Trimble said.

Adding fallen trees and other pieces of wood to the river slowed stream flows and created protected pools, which prevented spawning gravels and juvenile fish from being washed downstream.

NOAA Fisheries’ Office of Habitat Conservation more recently also awarded the McKenzie Watershed Alliance $7.6 million to restore lower Quartz Creek, a tributary of the McKenzie. Project partners have replaced an aging bridge that constricted water flow from Quartz Creek, causing water to gush like a firehose, blasting salmon and sediment downriver.

Slowing the water flow down is expected to keep juveniles from being flushed out and also help keep spawning gravels in place.

The next step is to restore floodplain habitat around the creek. Floodplains give juvenile salmon a place to escape fast-moving winter flows and provide access to highly nutritious organic matter and insects.

The floodplain absorbs excess water during winter storms and increases groundwater connectivity throughout the watershed, keeping the river flowing through the summer months.

The 2020 Holiday Farm Fire severely impacted the watershed, resulting in increased flooding and significant erosion. Higher levels of sediment made it harder for fish to breathe and decreased water quality for downstream residents.

The restoration work will increase groundwater and expand the amount of wetlands, which can reduce the impact of forest fires.