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EPA Science Matters Newsletter: What is Green Infrastructure?

Published September 2014

Slow it down. Soak it in. Naturally. 

Green infrastructure refers to natural vegetation, landscape design, and engineered techniques that retain, absorb, and often cleanse stormwater runoff. By including such features throughout a community, stormwater and other runoff from wet weather or spring thaws is retained, absorbed, and often naturally filtered.

Green infrastructure prevents or reduces the amount of runoff from flowing directly into storm drains where it can overwhelm the sewer system and end up contaminating local waterways   

Below are some green infrastructure techniques.

Bioswale: “Bioswales” are long, narrow depressions or channels designed with absorbant soils or other substrates, and planted with deep-rooted vegetation. They provide a way to filter, retain, and route excess stormwater away from where it is not wanted. They are particularly suitable along streets and parking lots.

Natural and Constructed Wetlands: Natural wetlands play a major role in absorbing and filtering stormwater. Engineered systems designed and constructed using wetland vegetation and soils, together with their associated microbes, can be installed in ways that mimic natural processes that retain and filter wastewater.

Green Roof: Roofs covered with growing media and vegetation absorb rainfall where it can be absorbed by root systems or retained for evapotranspiration later. EPA research has shown such roof systems are economically effective in urban areas where property costs and stormwater management costs are high.

Permeable Pavement: Hard surfaces constructed from pervious concrete, porous asphalt, permeable interlocking pavers, and other materials that allow rainwater, and ice and snow melt to penetrate rather than flow off can be important aspects of green infrastructure. 

“Green” Parking Lots: Integration of permeable pavement, bioswales, and rain gardens into parking lots allows property owners to manage stormwater on site. Such features also help mitigate urban heat islands and can create more pedestrian-accessible communities.

Planter Boxes: Urban rain gardens with vertical walls and open or closed bottoms collect and absorb runoff from sidewalks, parking lots, and streets. Planter boxes are ideal for space-limited sites in dense urban areas and as a streetscaping element.

Rain Barrel: A system that collects and stores rainwater from a roof that would otherwise be lost to runoff and diverted to storm drains and streams.

Rain Garden: Rain gardens (also known as bioretention or bioinfiltration cells) are shallow, vegetated basins that collect and absorb runoff from rooftops, sidewalks, and streets.  They mimic natural hydrology by absorbing and retaining water. Rain gardens are versatile features that can be installed in almost any unpaved space. 

Downspout Disconnection: Instead of downspouts leading directly to paved lots, sidewalks, or other nonpermeable surfaces, drainage pipes are re-routed to flow into rain gardens, rain barrels, or cisterns. 

Urban Tree Canopy: Trees reduce and slow stormwater by intercepting precipitation in their leaves and branches, thereby reducing and slowing stormwater runoff.