Strategic use of trees, green roofs, curb planters, and other features can reduce energy cost, reduce stormwater management fees, and increase property values
By Cooper Martin
The principles of low-impact design, distributed, small-scale stormwater infrastructure, and natural stormwater management to absorb rainwater where it falls are beginning to spread throughout the country. These strategies, collectively known as green infrastructure, are slowly replacing gray infrastructure in which water is collected and funneled through sewers to large, centralized treatment plants. For the sake of municipal budgets, the transition cannot happen quickly enough.
Sustainability professionals frequently advocate for these strategies because they mimic natural systems and provide other environmental benefits, such as reduced urban heat island, habitat restoration, and improved air quality. However, it is becoming increasingly clear that these strategies can be justified, and may even be necessary, when considered purely in economic terms.
Experience in cities throughout the country is beginning to demonstrate that green infrastructure is a better use of taxpayer or ratepayer dollars because it can alleviate urban flooding, improve neighborhood property values, and reduce long term capital and maintenance costs.
Urban flooding is a large and costly problem for local governments, causing an average of $8 billion in damages each year over the last 30 years (not including coastal flooding or storm surge). Interestingly, being located near a river or floodplain is not a very good an indicator of risk. In fact, the Center for Neighborhood Technology (CNT) conducted one of the most comprehensive analysis of urban flooding for Cook County, IL in 2013. Analyzing insurance data over a 5-year period, they found that “there is no correlation between [flood] damage payouts and the floodplains.”
Instead, the factor that most closely mirrored the flooding was amount of pavement and other impervious surfaces. Areas full of buildings, roads, and parking lots were catching and channeling more water than the engineered system could handle. Efforts such as the Los Angeles Green Alleys program and the Lancaster, PA Green Infrastructure Plan have successfully tackled similar urban flooding problems and shown that strategic placement of green infrastructure can dramatically reduce risk of flooding for many surrounding blocks by slowing or retaining some of this water during heavy storms.
Reducing flood problems alone would be enough to raise property values, but there are other factors that are catching the attention of commercial property owners. When deliberately incorporated into a new development or renovation, strategic use of trees, green roofs, curb planters, and other features can reduce energy costs, reduce stormwater management fees, and increase property values. Matt Gray, Sustainability Director for the city of Cleveland, is fond of saying that street trees are one of the only pieces of infrastructure that actually appreciate over time.
Most importantly, green infrastructure carries the potential to reduce long term costs for municipal stormwater management. For capital budgets, analysis of green infrastructure projects from the EPA and multiple independent sources typically agree that there can be a learning curve associated with design and construction that has resulted in higher costs for a few projects, but the majority of green infrastructure cases examined provide initial savings on site grading, infrastructure construction, paving, and landscaping. Additionally, since private developers have seen the value associated with green infrastructure it is possible for the private sector to share in the cost of stormwater management. There is greater buy-in for policies that require private building owners to treat and retain their stormwater through these value-add features as opposed to paying a fee to a centralized stormwater fund.
But what about maintenance? It stands to reason that planters, pervious paving, bioretention features, and other green infrastructure features would require more upkeep than the solid concrete and engineered treatment facilities. Indeed, it can appear expensive to provide staff and funding to maintain these features year over year while simultaneously ignoring the gray infrastructure as it works, invisibly, beneath the street. When the time comes to replace or expand that concrete sewer these one-time costs are often astronomical. Reducing this ‘spikiness’ and spreading the costs throughout an urban area and over a longer timeline can actually be a feature, removing the temptation for politicians to push costs farther into the future. The life-cycle costs already favor green infrastructure, and a recent CH2M study presented at the Water Environment Federation offers clear strategies to evaluate performance and further reduce costs.
None of this should imply that green infrastructure is simple or that it is fool-proof. There are more factors to consider in design, landscaping, and performance and public works employees will need to be trained to appropriately document and maintain a distributed network of installations. But the rising costs of heavy construction materials and labor have made it all but impossible for many cities to replace the aging stormwater infrastructure they currently have, let alone continue to expand. This is at least one case where environmentalists and economists can agree, and that should be enough to make any local elected leader smile.
Cooper Martin is the Program Director for the Sustainable Cities Institute at the National League of Cities. The SCI program provides information, tools, and guidance to strengthen communities and enable them to thrive while facing the challenges presented by a changing climate and uncertain global economy. He may be reached at firstname.lastname@example.org.