Cedar River Stewardship in Action

Seattle Public Utilities (SPU) used funds to expand the ongoing collaboration with Forterra and King County Noxious Weed Control Program (KCNWCP), known as Cedar River Stewardship-in-Action (SiA) to improve riparian habitat for Cedar River Chinook, coho, steelhead, and sockeye salmon. Working with willing riverside landowners, SiA controls knotweed and other invasive plant species, and restores native plant communities on the lower Cedar River. Before this grant project started in 2014, SiA had reduced knotweed infestations to 20% of the original area of infestation. This project targeted Cedar River riparian habitat from River Mile 21.7 to 5.6 in King County. With this funding, SiA treated 16.1 river miles of yet untreated knotweed and re-growth of previously treated areas on the mainstem and tributaries, and protected tributaries from new knotweed infestations. SiA surveyed approximately 456 acres of riparian habitat annually from 2014-2018, and treated all knotweed found, further reducing knotweed infestations to 5% of original infestation area.

SiA reached out to river-front landowners to recruit them as stewards of their own riparian habitat, and to offer free riparian restoration plantings, but no one was willing to participate. In order to achieve the riparian planting objectives of the project, SPU added native riparian trees and shrubs to a total of 21.9 acres of SPU-owned riverfront property (planting plans with plant lists are attached in PRISM). In 2016, SiA installed 6800 native plants on 19.4 acres, along approximately 6200 linear feet (1.17 mi.) of riverbank that has been a focus of ongoing riparian forest restoration. In 2017 SiA installed an additional 6200 plants in these same areas. In the winter of 2018, SiA planted the recently acquired Hamasaki parcel in the Upper Royal Arch Reach, installing 950 native plants in 13 elevated and browse-protected hummocks in a 2.5-acre restoration. The purpose of the hummock planting is to improve survival of the native planted community in areas of highly compacted soils, and to seclude it from animal damage that would prevent establishment. These Upper Royal Arch Reach plantings are farther from todays Cedar River shoreline, however, when the future floodplain and side-channel reconnection project (currently in design phase) is implemented, SPU expects these plantings will offer functional riparian habitat.

Seattle Public Utilities provided $41,913 and King County Noxious Weed Control Program provided $19,977. in matching funds for this riparian restoration project.

Project goals were to improve riparian habitat along the Cedar River for Chinook, coho, steelhead, and sockeye salmon.