Green infrastructure is a network of decentralized stormwater management practices such as preservation of undeveloped areas near a water source, green roofs, tree planting, rain gardens and permeable pavement. This paper gives an overview of the methods used to measure the benefits of green infrastructure on water, energy savings, improved air quality, climate change mitigation, urban heat island mitigation, improved community livability and improved habitat. Multiple case studies are provided.
Green infrastructure practices provide multiple environmental, economic and social benefits, including less polluted stormwater and increased property values. Examples of case studies demonstrating green infrastructure's economic benefits include:
The Milwaukee Metropolitan Sewerage District (MMSD) purchases undeveloped properties in areas expected to have major growth in the next 20 years and natural areas along streams, shorelines and wetlands. The purchased acreage is estimated to hold over 1.3 billion gallons of stormwater at a cost of $0.017 per gallon. One of MMSD’s flood management facilities holds 315 million gallons at a cost of $0.31 per gallon.
In Philadelphia, PA, officials learned that managing runoff through green infrastructure from 50% of the city’s impervious services would provide a net benefit of $2.8 billion, a net benefit 2,333% higher than managing it with a 30-foot tunnel, the traditional grey infrastructure option, which would provide a net benefit of $122 million.