Charles River Floating Wetland Pilot Project: Multi-Year Findings
Honor Award
Research
Boston, Massachusetts, United States
Sasaki Associates, Inc. + The Hideo Sasaki Foundation + Dr. McNamara Rome
Client: Charles River Conservancy
This project was fascinating to review. To see the progress of this project from concept to prototype to implementation was great. This project would seem to have a widespread opportunity for implementation everywhere. Clarity of intent and impact, excellent engagement in design, implementation and monitoring, great post installation impact gathering, and good results. Longevity and scaling are of interest. One of the best projects because it includes 3 years of post-installation research.
- 2025 Awards Jury
Project Credits
Sasaki, Lead Landscape Architect
Hideo Sasaki Foundation, Design Researcher & Project Co-sponsor
Charles River Conservancy, Dr. McNamara Rome, Principal Investigator
Massachusetts Department of Conservation and Recreation, Primary Public Partner
Foth Engineering, Marine Engineering and Permitting
Project Statement
The Charles River Floating Wetland Pilot Project investigates the application of Floating Treatment Wetlands (FTWs) as an innovative solution to improve degraded urban waters. This research addresses the linked challenges of missing habitat, degraded water quality, and impoverished public perception of urban waters. By combining scientific research, design experimentation, and public outreach, the project demonstrates how FTWs can enhance water quality, support biodiversity, and provide educational opportunities. The findings offer a defensible method for sizing FTWs and highlight their potential as an effective tool for landscape architects to address urban water quality challenges and foster environmental stewardship.
Project Narrative
The processes of urban development radically alter urban water bodies. Engineered drainage systems, land use changes, and loss of wetland habitat have resulted in water bodies with high levels of organic loading but limited natural pathways for processing pollutants. The Charles River Floating Wetland Pilot Project explores Floating Treatment Wetlands (FTWs) as an in-stream solution to improve water quality and ecological function in urban water bodies. FTWs are artificial, self-buoyant islands that support native wetland plants, providing habitat and removing nutrients from the water column. Synthesizing data from three multi-year pilots in Boston, Chicago, and Baltimore, this study focuses on phosphorus removal, ecological changes, and community engagement. The research addresses the challenges of translating short-duration lab and mesocosm experiments into practical, field-scale applications. This multi-year field study provides a defensible method for sizing FTWs to achieve specific water quality goals. Key findings include: Phosphorus Removal: FTWs achieve phosphorus removal through plant uptake. In this study, mass removal through harvesting of aerial vegetation was 2.3 g·P m⁻² year⁻¹. One acre of FTW can offset nutrient loading from 7-15 acres of dense urban development, comparable to infiltration-based green infrastructure and more effective than biofiltration methods and green roofs. Ecological Benefits: FTWs create measurable changes in biotic structure. Localized changes include increased abundance of native prey fish and increased mean body among large-bodied zooplankton. These changes are consistent with top-down control of algal biomass observed in healthy clear-water ecosystems. Community Engagement: The project serves as a platform for hands-on environmental education through STEAM kits, kayak tours, youth design sessions, and on-site experiments. Since its installation, 408 STEAM kits with informational materials in six languages have been deployed in local schools, enabling students to build their mini-floating wetlands and learn about river ecology. Kayak tours provide immersive learning experiences, while youth design sessions incorporate community feedback into future FTW planning. A solar-powered fish camera was installed to monitor fish populations. The research provides a basis for scaling FTWs in urban environments, offering landscape architects a new tool to address water quality challenges while enhancing ecological and social benefits. Along the Lower Charles River, where native wetland vegetation is scarce, FTWs provide critical habitat for small fish, foraging grounds for birds, and food sources for larval insects, and may serve as stepping stones in recovering urban waterways. For humans, access to urban blue spaces has been linked to improved well-being and reduced health risks. Future research must assess FTWs’ long-term impacts, scalability, and integration with broader green infrastructure. By merging science, design, and public outreach, the project demonstrates FTW’s potential to transform degraded urban waters into vibrant, healthy ecosystems and environmental stewardship. This project not only advances the field of ecological engineering but also provides a model for integrating innovative green infrastructure into landscape architecture. The findings highlight the importance of combining ecological interventions with community engagement for sustainable urban water management.