Collaborative Riparian Restoration on the Lower Cedar River

The Cedar River Watershed contains much of the best remaining aquatic habitat in the Lake Washington ecosystem and significant efforts have been undertaken to protect and restore it.  Salmonid populations, (Chinook, coho) show encouraging signs of resiliency, but long-term viability is at risk partly from widespread habitat degradation. It is imperative to improve ecological processes and riparian conditions essential to salmonid spawning and rearing.  While the upper two-thirds of the river are protected within the City of Seattle’s municipal watershed, which is closed to the public and managed as an ecological reserve, the lower one-third of the river is largely in private ownership in unincorporated King County and the Cities of Maple Valley and Renton. 

For over a decade King County and the City of Seattle have been acquiring and restoring river-front properties on the lower Cedar River.  While this work proceeds at a steady pace, land is expensive so only a small percentage of properties have been protected to-date. During this time, the appearance of the invasive plant known as knotweed along the banks of the lower Cedar River has necessitated a new strategy for riparian restoration.   Able to reproduce from tiny root fragments and occasionally from seed, knotweed takes over habitats near water, completely displacing native species, degrading habitat of salmon and other species, and potentially degrading water quality by destabilizing streambanks and causing increased sediment in the streams.  Knotweed is an aggressive, invasive plant that spreads rapidly downstream by flowing water and is extremely difficult and expensive to control. 

Recognizing the need to develop a new strategy to quickly address the knotweed problem, in 2010 a partnership was formed between Seattle Public Utilities, King County, Cascade Land Conservancy, Friends of the Cedar River Watershed and the watershed community to restore riparian ecosystems in the lower Cedar River on both public and private property. Efforts focus on encouraging landowner participation in activities that will contribute to riparian restoration, invasive plant eradication and native vegetation planting.  This presentation will provide an overview of the partnership’s progress in eradicating knotweed and other invasive plants; reestablishing native trees and shrubs; installing watershed best practices such as rain gardens and hedgerows; and building positive relationships between public and private landowners along the lower Cedar River.