Green Infrastructure: Definition and background

Green Infrastructure: Definition and background

What is green infrastructure?

Green infrastructure refers to systems or practices that use or mimic natural processes to infiltrate, reuse, or evapotranspirate stormwater on site. You may have also heard the term "low impact development" (LID). These two terms tend to be used interchangeably, but LID refers to the concept or approach to land development, while green infrastructure is about the actual system.

3-minute introductory video to green infrastructure

Types of green infrastructure

Rain gardens Bioretention cells
rain garden is a shallow, constructed depression planted with deep-rooted native plants & grasses. It's located to receive runoff from hard surfaces such as a roof, a sidewalk, or driveway. Rain gardens slow down the rush of water from these hard surfaces, hold the water for a short period of time, and allow stormwater to naturally infiltrate into the ground. Video on Rain Gardens or Bioswales. Bioretention cells often refers to installations that are designed and engineered to be more complex than home rain gardens in order to mitigate larger amounts of runoff. They are deeper and typically incorporate underdrains.
Green roofs Rain barrels
Green roofs, like the previous two types of green infrastructure techniques, reduce the amount of runoff and absorb/collect rainwater. They also serve to provide insulation and reduce the “heat island effect,” which often occurs in urban areas with a large amount of buildings and pavement. Rain barrels are used to collect and store stormwater runoff, typically from roofs through rain gutters. This allows for water reuse and reduces the amount of stormwater runoff which might otherwise end up in a curb/gutter system. Video on Rain Barrels.
Permeable pavement Water reuse
Permeable pavement work best in low-traffic areas. The pavement allows rainwater to pass through the pavement, into the earth below, thus reducing stormwater run-off. Where stormwater is collected and stored, water reuse is an option.  Using stormwater for irrigation reduces water consumption.  
Urban tree canopy Constructed wetlands
Urban tree canopy refers to the layer of leaves and branches covering the ground when viewed from above. This canopy intercepts rainfall and slows its movement that would otherwise fall onto paved surfaces and into storm drainage systems. It also reduces the urban heat island effect, reduces air pollution, increases property values, and provides wildlife habitat.
A constructed wetland is an artificial wetland, marsh or swamp built to serve several purposes including accepting/treating stormwater runoff, wastewater, or sewage.  Constructed wetlands are also used as wildlife habitat and land reclamation after ecological disturbances requiring mitigation. These systems help to remove pollutants from the water.
 Bioswales (vegetated swales) Streambank stabilization
Bioswales are open-channel drainage ways for stormwater. In contrast to traditional concrete channels, bioswales allow for infiltration, slow water movement, and can partially treat stormwater quality. Video on Rain Gardens or Bioswales. Streambank stabilization consists of practices such as matting, establishing vegetation, or installing riprap, to reduce or prevent erosion of stream banks.  Stabilization helps prevent sedimentation, reduces damage to nearby land uses, and improvemes habitats for fish and wildlife.
Rivers and lakes Greenways and streamways

Green infrastructure doesn't just refer to the structural practices mentioned on this page; it is a system that ties the developed landscape into the natural world, including rivers and lakes.  

 

 

Greenways are continuous corridors of undeveloped land, often connecting public lands and natural areas.  When greenways follow a river or brook, the corridors are called "streamways."  Greenways and streamways provide wildlife habitat, improve water quality, lessen flooding impacts, and enhance quality of life for residents. 
Infiltration basin  
  An infiltration basin is a shallow, artificial pond designed to infiltrate stormwater though permeable soils into the groundwater aquifer. They do not discharge to a surface water body under most storm conditions, but are designed with overflow structures.    

 

What's the important of green infrastructure (vs gray infrastructure)?

Gray infrastructure refers to more heavily-engineered systems for transporting stormwater, such as pipes and concrete channels.  They allow stormwater to travel faster, potentially creating erosion issues.   Gray infrastructure systems are also expensive to build (and sometimes to maintain) and when they’re undersized, flooding occurs. With gray infrastructure systems, pollutants are carried to rivers and lakes where they can create water quality issues.  Common pollutants include sediment, oil, metals, pesticides, fertilizers, yard waste, and general debris.

Compared to gray infrastructure, green infrastructure practices can reduce and potentially eliminate instances of flooding, sanitary sewage backup, and other property damage due to poor stormwater management.  A green system allows more time for pollutants to break down and be filtered by soil. Gray systems also allow stormwater to travel faster, potentially creating erosion issues. Because green infrastructure systems mimic or use natural systems and are designed on a smaller-scale, failure on a large-scale isn’t as likely. Green systems, like gray, do have maintenance costs, however, those costs are similar to managing a park or other vegetated area. Often with green systems, there is an added aesthetic quality to stormwater management.

 

How did green infrastructure get started?

Green infrastructure is a concept originating in the United States in the mid-1990s [Source]. One of the first green infrastructure projects was developed in 1990 in Prince George's County, Maryland.  A developer chose to build a new subdivision using rain gardens on each house's property, rather than installing BMP ponds.  This system, which cost 25% of a traditional system of curbs, sidewalks, and gutters, resulted in a 75-80% reduction in stormwater runoff during a regular rainfall event [Source]

 

Green infrastructure in Kansas

Several communities in Kansas have begun implementing green infrastructure practices and structures into their current stormwater management systems.  Read more about these on the Case Studies in and around Kansas page.

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