Floating Wetlands as a Cost-Effective Way to Achieve Ecosystem Services in Urban Rivers

Year: 2022
Presenter/s: Rob Zisette
Symposium Session: 2022 - 01 Addressing Climate Science + Environmental Justice
Topics covered: climate change, community involvement, tidal, urban, and wetlands


Global populations have become increasingly urban and as cities expand so have water quality and aquatic habitat impacts. Over half of the major urban centers are established on rivers, estuaries, and wetland areas that have been heavily modified. Constructed floating wetlands are a cost-effective method for establishing natural wetland ecosystem services to hard-edged urban environments and help manage the increased pollutant loading from stormwater and CSOs while also providing aquatic habitat and aesthetic benefits. In the evaluation of the efficacy of various approaches, we examine several example projects from the USA and EU extracting key lessons which can be transferred to other locations and scaled to specific site constraints. For example, the City of Rennes in France has recently installed 268 interlocking structural floating ecosystem modules with 6,800 native aquatic plants. This project is the largest floating riverbank of its kind ever constructed and provides wetland habitat in constant deep water with regular flood events rising over 2 meters.

In a second example, a series of floating ecosystems installed in the town of Hastings, UK is actively treating sewage-contaminated runoff and has been a key feature to improving water quality on a public beach. Water treatment by the floating wetlands reduced Enterococci by over 80% and E. coli by over 90% in this project. Similarly, in Manchester, UK a series of floating ecosystems on a public pond has been key to reducing chemical oxygen demand from >40 to <10 mg/L and increasing the water clarity from 0.3 to >1 meter. In Chicago, the NGO Urban Rivers has been carrying out mesocosm research and tests in partnership with the Chicago Botanic Gardens using water drawn from the Chicago River in a controlled experiment focused on evaluating the nutrient sorption capacity of floating wetlands over time. Meanwhile, a series of floating wetlands have been installed in the Chicago River with funding from sponsors including the Shedd Aquarium, National Geographic, Patagonia, and Whole Foods Market with plans set to expand the project into a mile long engineered urban wetland park called The Wild Mile. This presentation investigates these case studies examples in detail comparing water quality results before and after floating wetland construction and the resulting project outcomes and impacts.