“Green infrastructure” is defined as
an approach to wet weather management that uses natural systems—or engineered systems that mimic natural processes—to enhance overall environmental quality and provide utility services. As a general principal, green infrastructure techniques use soils and vegetation to infiltrate, evapotranspire, and/or recycle stormwater runoff.
Whereas, “grey infrastructure” is defined as follows:
In the context of stormwater management, grey infrastructure can be thought of as the hard, engineered systems to capture and convey runoff, such as gutters, storm sewers, tunnels, culverts, detention basins, and related systems.
The authors contend that communities and developers “can reduce energy costs, diminish the impacts of flooding, improve public health, and reduce overall infrastructure costs” by incorporating green infrastructure with grey infrastructure as an integrated system to control stormwater runoff.
The report includes examples of green infrastructure implemented or assessed in Washington, D.C. (green roofs); City of Cuyahoga Falls, Ohio (green infrastructure and flood control); St. Paul, Minnesota (Arlington-Pascal Stormwater Improvement project); Portland, Oregon (5-year Grey to Green Initiative); Philadelphia, Pennsylvania (green infrastructure assessment); and Los Angeles County, California (Emerald Necklace Green Infrastructure).
As noted in the conclusion,
The history of urban drainage and stormwater management in the United States has been written in the countless miles of buried pipes, sewers and tunnels that rush rainwaters out of sight and out of mind. This impression lasts only as long as it takes for runoff and its pollutants to burden our waters, back up into our basements, and flood our streets. While effective in their original purpose, these grey infrastructure approaches often create new problems, and provide only limited benefits to the communities they serve.
Today, communities are examining alternatives to managing stormwater runoff, and, as the authors note, “Ratepayers and taxpayers will likely insist on greater benefits and efficiencies for the investments they’re asked to fund.” The authors conclude, “[g]reen infrastructure promises cost-effective runoff management strategies that reduce or prevent flows of runoff into over-stressed sewer systems and waters, while providing tangible benefits to neighborhoods and communities. . . . Green infrastructure practices can also increase energy efficiency and reduce energy costs, mitigate flooding, and improve public health.”