Almost everyone in the stormwater business agrees that the terminology – along with the technology – has been changing. Between green infrastructure, low impact development, and “generic” stormwater management, the terms may mean different things to different people. Some history and a partial guide may help.
Low impact development, or LID (and sometimes said “lid,” like the top of a jar), was a term coined by Larry Coffman and his colleagues working in Prince George’s County, MD, in the early 1990s. In 1998, Coffman helped found the non-profit Low Impact Development Center that now uses this definition:
“Low Impact Development is a comprehensive land planning and engineering design approach with a goal of maintaining and enhancing the pre-development hydrologic regime of urban and developing watersheds.” The emphasis is on planning so that the ecological services of a non-developed site, such as groundwater recharge and pollution treatment, are retained after development by mimicking nature using site planning techniques such as distributed BMPs [best management practices] and open space preservation.
Tom Schueler, director of Chesapeake Stormwater Network, said, “Currently, there are probably 15 different terms for LID in the Bay states,” each prescribing specific practices or strategies such as an array of infiltration BMPs, minimizing street widths or the use of native plants.
Karen Firehock, director of the Green Infrastructure Center, reported that the term “green infrastructure” was first coined by the state of Florida in a 1994 report on land conservation strategies that culminated in several decades of strategic conservation planning. Green infrastructure planning meant identifying and protecting ecological networks (ecological hubs, linkages and sites along rivers, coastlines and across watersheds) and creating recreational and cultural networks, with trail corridors connecting parks, urban areas, working landscapes and cultural/historic sites.
For example, the James River is an ecological network, with bird-nesting sites and fish-spawning areas linked by the river itself. The Captain John Smith National Historic Water Trail along the James River is an example of a recreational and cultural network that also serves to highlight the importance of protecting the corridor's ecological network.
The EPA began to use the term “green infrastructure” around 2006 to refer to integrated stormwater best management practices that had previously been identified as part of the suite of LID strategies.
The current EPA definition of green infrastructure is “an approach that communities can choose to maintain healthy waters, provide multiple environmental benefits and support sustainable communities … that uses vegetation and soil to manage rainwater where it falls [and weaves] natural processes into the built environment.” Thus, green infrastructure provides stormwater management as well as flood mitigation, air quality management, community aesthetics and more.
Jon Capacasa, EPA Region III Water Protection Division Director, said that there was a debate about six years ago on how to use the terminology, but it has pretty much been resolved. Now, many use the term “natural infrastructure” to describe the networks of corridors, greenways and wildlife-based natural assets.
Some people use the term “green stormwater infrastructure” for clarity, and others use the shorthand LID/GI to cover all the bases.
Of course, there are other terms being used, including “blue infrastructure” used by some to denote structural changes to shorelines and waterways that mimic natural processes. Maryland equates blue infrastructure with the state’s aquatic resources and the ecological functions of aquatic systems that are “critical for commerce, recreation, energy, environment and … quality of life.”
There are also programs – such as Green Streets, Green Highways, Sustainable Sites – other strategies – such as “smart growth” – and certifications that can cause confusion. For example, LEED ™ certification may include elements of “green” site design and stormwater management, though it is primarily a building program that promotes “sustainable” – yet another confusing word! – design.
It’s good practice these days to use the terminology carefully – and to be clear about definitions because context and history are important. As Firehock wrote, “The key is to first ask, how can we avoid disturbing natural resources? Then, second, if we must disturb some area, how can we minimize the impacts? And lastly, how can we mitigate the harm caused?”