King County starts work to restore Cedar River to its ‘natural state’

Work has started on a major restoration project along the Cedar River that will reduce flood risks, improve habitat for Chinook salmon, and provide sustenance for southern resident orcas.

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The 52-acre project being completed by King County and partners will restore a mile-long portion of the river in south King County to its natural state. It will create slow-water, shallow habitat that is ideal for native Chinook salmon. The restoration will also build on the progress already made to protect people, homes, and infrastructure from flood risks along the river.

The Cedar River flows from the Cascades to the southern tip of Lake Washington.

“We are steadily restoring the Cedar River toward its natural state …,” King County Executive Dow Constantine said. “Our successful restoration projects upstream provide a model for a unified effort, guided by science to achieve multiple benefits for all living things that call King County home.”

The Rainbow Bend Restoration Project previously restored 40 acres of floodplain and reduced erosion risk to State Route 169 and the Cedar River Trail upstream. The Riverbend Restoration Project is located in unincorporated King County, between Renton and Maple Valley.

“We’ll protect more people, more homes, and more infrastructure from floods and erosion,” Constantine said. “We will provide the slow water that salmon need to rest, rear, and hide from predators.”

“Back in the mid-20th century, we would build hard structures that created narrow, fast-moving rivers that are challenging for salmon and require continuous maintenance to reduce flood risk,” he added.

The project will remove some levees and restore many of the natural flood plains in the stretch between Renton and Maple Valley. It will also make the flood plains more resilient as King County experiences heavier rain events as a result of climate change.

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The first phase of the project is expected to be completed by the end of the year, and the second phase by the end of 2022. The project design had to be modified after the river changed course through a levee and Cavanaugh Pond, a former gravel pit, during significant flooding in February.

“The goal,” according to the county release on the project, “is to more fully connect the floodplain by creating side channels and elevating the bed of the former gravel pit to provide better habitat for juvenile salmon and make it less enticing to predators, such as trout and bass, that prefer deeper waters.”

The Riverbend project is part of Constantine’s Clean Water Healthy Habitat initiative.

The KIRO Radio Newsdesk contributed to this report.