Many organizations solely focus on the bioretention and infiltration aspects provided by green infrastructure techniques. For example, the US Environmental Protection Agency defines green infrastructure as an approach that communities can choose to maintain healthy waters, provide multiple environmental benefits and support sustainable communities. There are many different green infrastructure techniques that communities and regions can use to facilitate their stormwater maintenance, water quality and runoff issues. Several of these techniques are featured below.
Bioswales: Bioswales, or vegetated swales, is a landscaping technique used to redirect and filter stormwater. Often used around parking lots or roads, bioswales filter pollution from surface runoff water. Bioswales collect runoff water, retain the water for a period of time and then allow the water to slowly drain into the ground. Bioswales usually contain native plants and grasses, like those used in rain gardens, that enhance water filtration and cooling.
Constructed Wetlands: Constructed wetlands are artificial wetlands created to simulate the benefits of a natural wetlands. Natural wetlands filter pollutants and sediments from the water and can effectively reduce flooding, which provides valuable stormwater and water quality benefits for a community. In the absence of a natural wetland, constructed wetlands can provide these benefits.
Greenways: Greenways, also called green alleys, are vegetated or pervious pavement areas located next to impervious surfaces like roads or parking lots, that help filter and reduce stormwater runoff. For example, Chicago’s Green Alley Program has converted 1,900 miles into green alleys that help water filter through its permeable surface, provide filtration through the presence of bacteria, and are lighter in color than traditional pavement which cools the surrounding area.
Permeable Pavement: Permeable Pavement, or pervious pavement, is a porous concrete that allows rainwater to seep into the ground. Allowing the water to infiltrate the ground rather than collect or runoff into a storm sewer, helps water the surrounding vegetation, recharges the ground water, helps preserve water resources, stormwater runoff quantities are reduced, the urban heat island effect is reduced which results in lower ozone levels, and the pavement stores less heat and reflects more light cooling the surrounding areas. There are four main types of permeable pavement: porous asphalt, pervious concrete, grid pavers and grass pavers. According to American Rivers, depending on the intensity of the precipitation event, studies have shown that pervious pavement can infiltrate as much as 80 to 100 percent of the rain that falls on a site.
Rain Barrels: A rain barrel is used to collect and store rainwater from a roof or rain gutter that would otherwise be diverted into the stormwater system. Water stored in a rain barrel can be used to irrigate lawns, gardens, and potted plants and for grey water systems (e.g. for toilet water). Rain barrels can be installed individually or as a component of a rain garden.
Rain Gardens: Rain gardens incorporate the installation of native vegetation on typically impervious surfaces such as roofs, walkways and parking lots. Rain gardens provide water retention and infiltration to reduce stormwater runoff and protect water quality. Typically, rain gardens are located at the bottom of a slope in order to successfully collect water runoff. The native vegetation is tolerant of the regions climate, soil and water conditions and therefore does not require fertilizer or a lot of maintenance. The native vegetation also serves to provide a habitat to local wildlife. According to Maryland’s Department of Comprehensive Planning, rain gardens can reduce pollutants reaching ground water tables and surrounding streams by up to 30 percent.
Stormwater Best Management Practices (BMP): Stormwater, although an essential process in our environment, requires critical consideration on how infrastructures and systems are maintained. Best Management Practices exist to manage stormwater to hydrate flora, maintain regional hydrology, avoid erosion, and reduce environmental contamination. In urban environments, it is most challenging to return stormwater to the natural hydrology due to the reduced areas of infiltration. With the proliferation of Green Infrastructure, more and more solutions are gaining traction and feasibility beyond the traditional “gray” options. For example, green infrastructure keeps stormwater out of the sewer systems by either containing water for later use in gardens and grey water systems, or allowing it to seep into the ground and be absorbed by plants or returned to the aquifer.