Depending on the type of work you do, “low-impact development” might be a distant buzzword or an integral part of your day-to-day vocabulary. If your work involves stormwater management, and particularly if residential or commercial landscape architecture, design, or installation is within your purview, you’re probably familiar with LID. Even if you’ve not yet dealt with it, it will likely influence your work in the not-too-distant future.

At StormCon ’06 in Denver in July, a panel of researchers and scientists discussed stormwater BMP trends, and LID was one of the subjects they addressed. As one of the panelists noted, there are probably hundreds of definitions of LID, but it’s most often understood as mimicking or replicating the predevelopment hydrology of a developed site. Despite an increase in impervious surface area, no more water should flow off the site than before it was developed. Panelist John Sansalone, a professor and stormwater researcher at the University of Florida in Gainesville, noted that because water quantity and quality are coupled in an urban environment, if we can manage a site’s hydrology we are likely to influence water quality as well.

Some communities are encouraging the use of LID and even writing it into their local ordinances. As LID becomes more widely adopted as a stormwater management strategy—treating water where it falls rather than moving it offsite—it will affect erosion control practices, channel protection, and stream restoration downstream of the areas where it’s practiced.

In practical terms, LID involves a number of lot-level techniques: rain gardens in homeowners’ yards; porous pavement, concrete, or pavers in driveways, parking lots, and access roads; vegetated swales; green roofs; and other means to retain and infiltrate stormwater. Panelist Bruce Ferguson, a landscape architect and director of the School of Environmental Design at the University of Georgia, pointed out one of the stumbling blocks some cities run into when dealing with LID: It requires creative thinking and must be designed into each development on a very site-specific basis; “You can’t buy it,” he said.

Another concern is the ongoing maintenance of LID practices—or, more basically, just keeping track of what and where they are. LID involves many small, dispersed elements rather than (or sometimes in addition to) massive, publicly owned stormwater infrastructure. As homes and businesses are bought and sold over the years and as homeowners’ associations change members, will people remember what the rain garden is for, or that the porous pavement in the parking lot might need an occasional vacuum cleaning to keep it functioning? It’s clear that a city or county department is responsible for the storm sewer system, but responsibility for hundreds of LID components is less obvious.

For these two reasons—its close ties to the sites on which it’s practiced, and the ongoing need for people to keep an eye on it—LID seems a natural domain for those working in the erosion and sediment control arena. The work ESC professionals perform is by necessity always site-specific; we’re never far from the ground. While it’s not accepted everywhere, and not appropriate in every location—it’s less feasible where groundwater tables are high, for example—LID is in many ways the ideal form of erosion prevention: Anything that reduces the volume of runoff makes the job easier.

More information on LID is available from the EPA (also part of the agency’s “Smart Growth” initiative, www.epa.gov/smartgrowth) and from the nonprofit Low Impact Development Center (www.lowimpactdevelopment.org). The IECA and regional StormCon conferences also periodically offer LID workshops. A full-day class on LID is scheduled for November in Seattle (www.stormcon.com/seattle).

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EC - September/October 2006