Green Infrastructure 101

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5036625486_e60cef8f76_bIn today’s changing climate, planning for natural hazard mitigation and the reduction of wet weather impacts is a top priority, particularly in coastal communities and flood-prone areas. Communities with growing populations face additional pressures, as more people and increased development strain existing water infrastructure and a place’s capacity to weather storms. In light of these challenges, green infrastructure represents one way towns and cities can better manage stormwater and help increase their resiliency. 

What is green infrastructure?

In conventional gray stormwater infrastructure, stormwater is routed through a network of gutters, sewers and other engineered collection systems, ultimately discharging into a river, lake or ocean. As it travels, this stormwater picks up trash and other pollutants that get carried along.  Heavy storms can overwhelm these water collection systems, causing erosion and flooding. In contrast, green infrastructure uses both natural and man-made design elements to better manage stormwater at its source, through improved filtration and absorption. The U.S. EPA describes green infrastructure as a system that uses “vegetation, soils and other elements and practices to restore some of the natural processes required to manage water and create healthier urban environments.”

What does this look like at a community level? Green infrastructure encompasses design elements like rain gardens, rainwater harvesting cisterns, green roofs, street infrastructure improvements like bioswales, and stream restoration efforts, including stream daylighting. All of these efforts are designed to enable stormwater infiltration at its source, and to reroute stormwater before it enters the sewer system. Replacing asphalt and other non-pervious surfaces with permeable pavement is another key element of green infrastructure. Natural landscaping features like forests, meadows, open spaces and floodplains can also be incorporated as part of a community’s green infrastructure.

Does it cost more to implement green infrastructure? 

As with any infrastructure improvement project, municipalities may be concerned that implementing elements of green infrastructure will carry costs that are higher than just maintaining typical gray stormwater infrastructure. But research and community experience suggest that green infrastructure can be cost-effective, especially once its multiple environmental and community benefits are considered. Improved water quality, reduced sewer overflow, improved aesthetics and increased urban greenspace are some of the environmental and social benefits communities can enjoy from green infrastructure. For example, parks and open spaces serve a dual purpose as both recreation space and stormwater management element. Public investment in this type of green infrastructure can thus be an important driver of adjacent economic development.

Of course, it can be difficult to monetize these types of benefits associated with green infrastructure. There are tools that assist in this regard, such as the U.S. Forest Service’s i-Tree program, which provides forestry analysis and benefit assessment tools. The Center for Neighborhood Technology has a detailed guide to valuing the economic, social and environmental benefits of green infrastructure, which includes tools and references for quantifying long-term benefits associated with green infrastructure.

In North Carolina, municipalities seeking to finance water infrastructure improvement projects can turn to the state’s Division of Water Infrastructure for assistance. Created in 2013, the Division of Water Infrastructure administers several funding programs that had previously been spread across the state’s Division of Water Quality, Division of Water Resources and Department of Commerce. Low interest loans and grants are available through a variety of programs designed to help communities improve their water infrastructure.

Green Infrastructure Case Study in North Carolina

In Charlotte, the biggest threat to the area’s drinking water quality comes from increased stormwater runoff brought by the region’s rapid pace of development. In order to protect the area’s water quality, Charlotte-Mecklenburg Storm Water Services used watershed modeling and found that green infrastructure and low impact development were the only approaches that “could achieve sufficient pollutant removal and prevent further degradation of the county’s waterways.” The County undertook a cost-effectiveness analysis of different stormwater management approaches, and found that for urban retrofit projects, stream restoration was the most cost-effective way of preventing sediment deposition in streams. As a result, green infrastructure elements like in-stream restoration, reforestation, rain gardens and bioswales are now implemented in the County’s approach to stormwater management.

The ongoing restoration of Charlotte’s Little Sugar Creek is one example of the County’s successful implementation of green infrastructure. In 2000, the County embarked on a Little Sugar Creek Greenway and stream restoration effort to deal with the creek’s increasing pollution, reclaim its natural flow, and improve its water quality. When complete, the greenway will include over 19 miles of trails designed for bikers, pedestrians and other recreational users, running from uptown Charlotte down to the South Carolina state line.

The greenway and stream restoration efforts are being funded by both public and private actors, and “every dollar spent on the greenway is expected to generate at least $3 of private development.” A 1.29 mile stretch of completed greenway and stream restoration that runs in Charlotte’s urban core was designed to include public amenities like plazas and event spaces, which have been used to host a variety of events and festivals, highlighting the potential for green infrastructure to serve the dual purpose of improving stormwater management while providing community benefits. This section of the Sugar Creek corridor has also seen new mixed-use development with the opening of the Metropolitan Complex, a mix of restaurants, shopping and apartments.

As the greenway is being developed, Charlotte-Mecklenburg Storm Water Services has been implementing a variety of green infrastructure projects along Little Sugar Creek—including planting native vegetation, removing concrete caps and dams that interrupted the stream’s natural flow and demolishing buildings that repeatedly flooded—efforts that have improved water quality and reduced stormwater impacts.

Elizabeth Packer is a second year Master’s student in the Department of City and Regional Planning at UNC Chapel Hill and a Community Revitalization Fellow with the Development Finance Initiative.

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