Once, cities were built to channel storm water away from building foundations and roadways. But as urban areas have grown, rooftops, streets and other impervious surfaces have disrupted cities’ natural hydrology. Today, everyone from water authorities to home gardeners are looking to absorb rain where it falls, eschewing traditional treatment plants and underground sewerage tunnels that effectively neutralize runoff, but don’t do much else.
The first of these projects matured in Portland, Oregon, and Prince George’s County, Maryland. Now, dozens of cities including Washington, Philadelphia, and Louisville have embarked on their own overhauls.
They are attracted, in part, by the lower cost of planting trees and gardens and retrofitting streets, parking lots and roofs. But it’s also a matter of pay-off. Taxpayers never see the underground fixes. But green infrastructure is something people can use and enjoy, says Joan Furlong, program manager at the Rock Creek Conservancy, a D.C. nonprofit group working with city officials to recruit residents and business owners to the RiverSmart Program.
“It’s become a really hot topic in the last five years or so. Before that green fixes weren’t really accepted by the regulatory agencies,” Gardner-Andrews says, particularly the EPA, which first publicly endorsed green infrastructure just five years ago.
The agency now endorses planting greenery to absorb rainfall as an important tool for adapting to rising sea levels and more extreme storms.
Wildlife also benefits. For instance, if you live in Maryland, planting White Turtleheads in your rain garden can provide much needed habitat for the state butterfly, the Baltimore Checkerspot, which will only lay its eggs on Turtlehead leaves, says Carole Barth, an environmental planner with the Department of Environmental Resources in Prince George’s County, Md.
But doing a rain garden requires careful site planning, experts say. If planted too close to buildings, they can exacerbate rather than alleviate basement flooding. And it’s important to find a patch of land where water percolates well through the soil, which is not necessarily the case everywhere. Researchers have found years of mowing and other activities sometimes leaves the ground so compacted that its about as permeable as concrete.