Planopedia

Nature can also be infrastructure, harnessed for its ability to provide a variety of beneficial services to communities, such as protections from floods, mitigation of heat, habitat for wildlife, and improved air and water quality. 

As the world begins to reckon with the effects of climate change and the other negative outcomes of traditional 20th century infrastructure, like air pollution from cars and water pollution from industrial-scale business operations, the use of green infrastructure has become more common as a feature of sustainable and regenerative environments.

Historically, infrastructure planning and building has relied on engineering and man-made structures—such as gutters, pipes, tunnels, and dams—to attempt to remove or limit environmental effects. Stormwater is channeled into a storm drain and quickly pushed out to the ocean, for example. The shortcomings of such "gray infrastructure" systems have become more apparent with climate change and the birth of the environmental movement. As it tuns out, some gray infrastructure systems only exacerbate environmental risk. Green infrastructure acknowledges those shortcomings and implies, by comparison, a decision to live with and learn from nature. 

Planning Green Infrastructure

Green infrastructure can be planned and implemented at multiple scales—from the hyperlocal scale of individual properties and neighborhoods to the regional scale of watersheds and public lands. At the hyperlocal level, green infrastructure can take the form of green roofs, rain barrels, bioswales (i.e., a form of drainage that uses plant life and organic matter to filter water as it seeps into the ground), and trees. At the regional level, wildlife corridors ensure biodiversity by providing animals with safe passage above or below man-made features like roads and highways and watershed planning can allow for space for rivers to overflow for flood protection and to encourage plants and animals to flourish.  

Importantly, much of the driving force behind green infrastructure planning comes from federal policies like the Clean Water Act and the Clean Air Act. To help spur the adoption of green infrastructure systems, for example, Congress enacted the Water Infrastructure Improvement Act in 2019, which defines green infrastructure as "the range of measures that use plant or soil systems, permeable pavement or other permeable surfaces or substrates, stormwater harvest and reuse, or landscaping to store, infiltrate, or evapotranspirate stormwater and reduce flows to sewer systems or to surface waters."

Examples of green infrastructure are numerous, including the following:

• Bioswales
• Downspout disconnection
• Rainwater harvesting
• Rain gardens
• Forests and nature reserves
• Land conservation
• Wildlife habitat and corridors
• Constructed wetlands
• Green streets 
• Permeable pavements
• Green alleys
• Green roofs and walls 
• Planter boxes
• Urban tree canopy

In planning documents, green infrastructure is also sometimes referred to as “low impact development,” “environmental site design,” or “low-carbon infrastructure.” Blue-green infrastructure is another fairly recent term that can be hard to distinguish from the term green infrastructure (but blue-green infrastructure usually refers to urban water systems without setting aside as many gray infrastructure systems).

An Expanding Definition

According to numerous sources, green infrastructure is most commonly applied to the practices and processes of stormwater and water supply management. A study published in January 2022, for example, found that most plans focusing on green infrastructure in the United States are intended to address the regulations of the federal Clean Water Act. 

The same study suggests a definition of green infrastructure than includes natural stormwater mitigation practices, but also expands to include the infrastructures of the larger landscape. While most of the planning and design world's adoption of green infrastructure has focused on water, numerous other forms of green infrastructure are gaining in popularity too, such as the creation of networks of open spaces, such as farmland, public land, parks, urban forests, conservation development, urban growth boundaries, bike and pedestrian paths, and other greenways that preserve a place for the natural world alongside built environments, cleaning the air and maintaining biological balance. 

To be clear, green infrastructure can also incorporate engineered systems into the natural environment, but the key is that even these engineered systems will, by definition, mimic or harness the powers of nature for the benefit of nature. Hydroelectric dams are not green infrastructure, for example, despite harnessing the power of nature for water storage and electricity generation because of their tremendous impact on species habitat and even the weather.

The term green infrastructure can be easily abused, like so many terms central to environmental causes. It is not enough, for example, to throw the word green in front of a common feature of gray infrastructure and say you're doing your part of sustainability and environmental protection. While searching for examples of green infrastructure online, for example, you might find some examples of some questionable applications of the term, such as "green parking garages," for example. 

Green infrastructure can be defined both by its structures, the natural processes of plants, soil, and topography, as well as its output is how it creates resources and benefit where before there was pollution and  It mimics natural hydrological processes and uses natural elements such as soil and plants to turn rainfall into a resource instead of a waste.