PNW 98 Session - Full Abstracts

Full Abstract

SCOTT MOORE (1)
Bob Aldrich (2)

(1) Tsuga, Seattle, WA
(2) Snohomish County Public Works SWM, Everett, WA

Silver Creek Marsh Habitat Restoration Demonstration Project

The Snohomish County Native Plant Salvage Program is leading a habitat restoration project on Silver Creek, located in south Snohomish County. Silver Creek is a coho and cutt-throat bearing tributary of North Creek in the Lake Washington watershed. Silver Creek Marsh, a Snohomish County Public Works Capital Improvement Project was designed and constructed to reduce flooding of adjacent homeowners, improve habitat for anadromous fish, and provide open space for nearby residents. While deemed a successful engineering project, most of the vegetative components of the project failed. The Native Plant Salvage Program, several cadre of willful volunteers, and a crew of displaced timber workers were recruited to "fix" the site.

The Snohomish County Native Plant Salvage Program enlists volunteers to "rescue" native plants from areas slated for development and land clearing, nurtures the salvaged plants in controlled holding facilities until plant vigor is re-established, then plants out these native plants in stream, wetland, and riparian restoration projects. The value of volunteer plant salvage programs is well known: properly run programs can be cost effective, provide educational and outreach opportunities, provide plants with high genetic fidelity to a given ecoregion, and foster stewardship through community based projects.

Site investigation of the Silver Creek Marsh site revealed several factors limiting successful establishment of vegetation: lack of top soil, placement of plants in "pits" carved into impermeable glacial till, seeding of competitive grasses and legumes common in meadow mixes, lack of maintenance during the establishment period, grazing by waterfowl, and trampling by local park visitors.

Initial priority was to establish vegetative cover along the stream corridor for juvenile salmon refuge and water temperature attenuation. Salvage topsoil held in place with coir, jute soil bags, fascines, and live stakes provided a substrate for dense plantings of locally salvaged native plants which were watered and heavily mulched. Newly planted segments were isolated with plastic construction fencing while leaving sacrifice areas for access to the stream and wetland edges. First season plant growth was successful and vigorous. Adjacent areas are being evaluated, treated, and planted in similar fashion area by area.

Successes at Silver Creek Marsh provide an impetus to educate and nurture non-botanists in Public Works departments to integrate native plants into project designs and not treat plants as surficial landscape elements. Phased demonstration projects create local successes, provide natural labortories for new methods, and prove that doing it right the first time is always less expensive.

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