What is Green Infrastructure?
Green infrastructure is a term that is used to encompasses practices that use plant or soils systems, permeable surfaces or substrates, stormwater harvest and reuse, or landscaping to store, infiltrate, or evapotranspirate stormwater and reduce flows to surface waters or sewer systems. It’s an approach that protects, restores, or mimics the natural water cycle. It could involve planting trees, restoring wetlands, installing permeable pavements, or installing a bioretetntion area or rain garden rather than building a costly new water treatment plant.
Why Choose Green Infrastructure?
Green infrastructure has a number of benefits, which include improving water quality and quantity, air quality, climate resiliency, habitat and wildlife and communities. GI practices retain rainfall from small storms, which reduces stormwater discharges to our local waterbodies. In addition to retaining water, these practices also treat stormwater to remove pollutants. The vegetation associated with some of the practices can have a positive impact on smog as vegetation can reduce smog by reducing air temperatures and removing air pollutants.
A green roof is a layer of vegetation that is grown on a rooftop. Green roofs provide shade, remove heat from the air and reduce the temperature of the roof surface and surrounding air. There are two types of green roofs: extensive and intensive. Extensive green roofs are simpler with hardy plants and a growing medium depth of two to four inches. Since the growing medium is shallow, they require the least amount of added structural support. Intensive green roofs are more complex and resemble gardens and parks. They require structural support due to the weight and have high initial investment and high maintenance costs.
Bioswales are parabolic or trapezoidal channels designed to concentrate and convey stormwater runoff while removing pollutants and debris. Bioswales can also be beneficial in recharging groundwater. They can be planted with turfgrass or vegetated with grasses, shrubs, and perennials; xeriscaped or be wet swales and function similar to wetlands.
Bioretention areas are landscaped depressions that are used to capture, slow, and treat stormwater runoff. They consist of a four-foot deep planting soil bed, a surface mulch layer and a six-inch deep surface ponding area. Landscaping with native vegetation is critical to the performance and function of bioretention areas.
Stormwater ponds are practices that capture stormwater runoff from each rain event and detains the water in a permanent pool of water or a combination of a permanent pool and extended detention.
Stormwater wetlands are practices that create shallow marsh areas to treat stormwater and often incorporate small permanent pools and/or extended detention.
Rain gardens are shallow depressions intended to manage and treat small volumes of stormwater runoff from impervious surfaces. They are a simplified version of bioretention and are designed as a passive filter system. This practice is most commonly used in residential settings to capture roof runoff or other drainage.