Lydia Lee writes about architecture, design, and urban planning from the Bay Area for publications including Architectural Record and the San Francisco Chronicle. She was previously the San Francisco editor for the Architect's Newspaper. She serves on her local bicycle commission and fusses over two beehives.
The brains behind Scotland's Biomatrix Water use flotillas of plants to filter polluted water and soften concrete riverbanks.
About 10 miles west of central London, Hanwell is one of the towns that sits along the River Brent, a tributary of the Thames. As is true with many urban rivers, the Brent is bordered by concrete walls as it flows through towns and has been heavily polluted by industrial effluent and sewage.
Recently, a local environmental nonprofit called the Canal and River Trust wanted to restore the natural riverbank, but was thwarted from taking out the concrete retaining walls because of concerns over flooding. But the group found a clever alternative—a system of floating wetlands that would bring back the natural edge.
Within a year of installing the system, the riverbank has been utterly transformed, the diversity of plant species has gone from three to 30, and dragonfly larvae—a good indicator of water cleanliness—are in abundance.
The particular system at Hanwell was designed by Scottish company Biomatrix Water, which has worked on projects with global architecture and landscape design firms such as AECOM and SWA. It is one of a handful of companies offering commercial versions of a simple concept: a floating platform that gives plants and animals a place to live in rivers, harbors, and other urbanized waterways.
The Biomatrix design consists of a base of recyclable plastic and stainless steel that is designed to last 50 to 100 years; it is secured to posts along the bank or anchored below, allowing it to rise and fall with the water level. To jump-start the restoration process, it is planted with native water plants. Over time, the floating nurseries are colonized by wild plants that take advantage of this new waterfront. They provide much-needed shelter for fish, waterfowl, and birds.
In addition to measurable increases in biodiversity, research on floating wetlands reports significant improvement in water quality, showing reduced levels of organic matter, suspended solids, agricultural runoff, and metals. Floating wetlands can also boost traditional methods of water treatment. In one study, a system from Floating Island International of Montana, installed in a wastewater lagoon, was able to remove 52 percent more nitrogen—a major problem stemming from agricultural runoff—than another lagoon on its own.
Biomatrix Water has installed floating islands in Hicklin Lake, Seattle, and is currently working on a harborside nature trail in Bristol in southwest England, as well as a 1.2-mile riverfront project in Zhenjiang, China. "These technologies provide a toehold for natural systems to take root," Fulford says. "There is real potential for nature and humanity to work together."