July 25, 2019

Floating Wetlands Research & Education

In 2013 and again in 2017 and 2018, the Green Futures Lab conducted seminars on floating wetlands. Students surveyed floating wetlands literature and precedents, investigated their benefits for habitat, stormwater cleansing and water temperature regulation, and then developed new design concepts for several freshwater locations. Each site’s biological parameters drove the designs. Carrying the momentum of the first seminar, students designed, built and installed 360 square feet of floating wetlands to provide shade and habitat in a Redmond, WA wetland. A student leader continued to monitor the results, and also to design, build, and monitor additional prototypes with support from the GFL, King County, and the Society of Wetland Scientists. Students in the 2017 seminar designed and constructed prototypes of floating wetlands for six sites in the Lake Washington Ship Canal and in 2018 for sites in the Duwamish River designed specifically to exclude predators and provide refuge for out-migrating juvenile salmon. With a grant from the UW Campus Sustainability fund, the GFL investigated the feasibility of using such floating habitat structures to replace lost shoreline habitat along the critical Ship Canal corridor.

Studies from the 2013 seminar are summarized in Floating Wetlands Research and Design Investigations, Volumes I + II.

Duwamish Floating Wetlands Project

The Duwamish Floating Wetlands project examined if constructed floating wetlands can increase salmon habitat and improve water quality to support the

survival of out-migrating juvenile salmon. The constructed floating wetlands were designed, tested, and deployed in the Duwamish River Estuary by the UW Green Futures Lab team and UW Landscape Architecture classes. Four “Biobarges” were constructed to hold constructed floating wetland “Biofilters,” while also providing platforms for researchers to access them. A team of GFL researchers and community scientists monitored these innovative floating wetlands to gather information about juvenile salmon interactions with the BioBarges, invertebrate production, plant growth, and water quality improvement. The community science program was developed to encourage collaboration between students and community scientists in performing the field research and to connect community scientists to the research and to the river.

After the first summer (2019) of research in the lower estuary, the units were modified based on the year 1 research to improve salmon habitat qualities. As a result, they were moved further upstream and then monitored for a second summer (2020). For more information on the design process and plant growth, see an article in Restoration Ecology. The GFL team developed full reports for both 2019 and 2020 research years, with results also informing as School of Marine Affairs Capstone Report. For more information on the community science program, an article has been published in the journal Socio-Ecological Practice Research. This project was funded by King County Waterworks, Councilperson Jeanne Kohl-Welles, the Rose Foundation, Puget Sound Keepers, and the Port of Seattle.

Sweetgrass Living Shorelines Project

In 2021, the Sweetgrass Living Shorelines project used findings from the Duwamish Floating Wetlands project to inform the implementation of units along the Lake Washington Ship canal and in Lake Union. The floating wetlands were adapted to site conditions along the bank. Piers provided protection at the Fremont Bridge and along the exposed shoreline. At South Lake Union Park, GFL staff and community scientists constructed the prototypes over two years to learn of potential habitat benefits. Team members also initiated the Sweetgrass Arts Project, inviting artists to contribute design and poetry pieces that were displayed at the floating wetlands and along the Burke Gilman Trail.

Sweetgrass Marine Floating Wetland

In 2022, in partnership with Earthcorps, the UW Green Futures Lab team launched a Marine Floating Wetland at Shilshole Bay Marina. This project is being maintained by the GFL team and stewarded with the assistance of Shilshole Bay community members.

Nancy Rottle and Mason Bowles, our team leads, were recently interviewed on the Urban Rivers Podcast. Check it out!

The GFL also created and maintains the Living Shorelines Website.