Using design and engineering, there are many ways that buildings, plantings, or other structures can absorb stormwater runoff, reduce the urban heat island effect, and improve air and water quality in a city. These practices are called green infrastructure (GI).
GI can help cities save money and improve environmental quality for ecosystems and humans. Stormwater runoff, particularly in combined sewer system cities where runoff and sewage share infrastructure, can lead to higher water treatment costs, flooding, and loss of water quality and ecosystem well-being. It can reduce runoff loads by creating more permeable surfaces, which slow the velocity of runoff and filter pollutants out of water before it seeps into groundwater sources or goes into streams and rivers. Higher urban temperatures compared to the surrounding landscape, termed the urban heat island effect, can have negative health and safety implications especially in the most vulnerable populations that inhabit our cities. Higher temperatures on the already hot summer days can elevate the risk of stroke for the elderly and affect the youngest. GI strategically utilizes vegetation in most of its applications, which cools a space through evapotranspiration. Vegetation found in GI can also filter city air and improve overall air quality. It can also serve as a carbon sink for our intensive transportation demands and resulting emissions. Finally, GI can beautify a city through well-designed rain gardens, green roofs, urban wetlands, and other structures.
Figure 1. Bioswales in New York City are a part of a larger GI initiative led by the Department of Environmental Protection (DEP). Bioswales are landscape features that remove pollutants from surface stormwater runoff. Photo Credit: DEP Flickr page.
However, to achieve large scale GI applications, cities need take a more collaborative approach. Currently, cities tend to use a fragmented approach to GI, which is inefficient and yields limited results, because of the lack of strategically placed infrastructure. For example, the United States Environmental Protection Agency (EPA) suggests that one way to incorporate GI is to designate a GI district downstream from a high density development. Incorporating this type of district, however, likely requires a high level of collaboration between different stakeholders and not a fragmented approach. The entities that play a role in this fragmented arena are educational and research organizations, city planning and water management departments, as well as other departments that carry out the day-to-day functions of a city. Research and education materials on GI and its benefits are produced by one entity, while general city plans are developed by another department, and yet another department develops a stormwater management plan. Ideally, these components should be a part of a collaborative effort, which, while maintaining individual department boundaries, would bring their outputs together to create a holistic approach. Research and outreach materials should inform stormwater and city planning and general city plans should consider future stormwater management and its potential dependencies on GI. There are various distinct and successful approaches to widespread GI implementation that serve as examples for other cities to follow when devising a strategy to conduct GI in a more robust manner. New York City and Los Angeles are examples of cities that have a more integrated and widespread GI networks, while Houston is an example of a less vigorous GI effort, but it is starting to move towards this collaborative approach.
Compared to the 10 largest cities in the U.S., New York has one of the largest amounts of rainfall, which results in a heightened demand for water treatment. Backed by the then-Mayor Michael Bloomberg, PlanNYC is a comprehensive climate adaptation plan that brought together organizations of diverse backgrounds to foster a “Greener, Greater New York,” mainly focusing on the “physical city, and its possibilities to unleash opportunity.” The plan’s creators “have examined the tangible barriers to improving our daily lives: housing that is too often out of reach, neighborhoods without enough playgrounds, the aging water and power systems in need of upgrades, congested roads and subways. All are challenges that, if left unaddressed, will inevitably undermine our economy and our quality of life.” To start, the New York City Department of Environmental Protection (DEP), the organization that manages the plan, set forth initiatives such as the Greener Greater Buildings Plan, Clean Heat Program, Million Trees Program, and the Green Infrastructure Plan to complement the larger scale plan. Additionally, the Center for Clean Air Policy provides financial measures that inform the city about the costs and benefits of the Green Infrastructure Plan. Several GI projects have already resulted from this comprehensive plan, including the Bluebelt System in Staten Island and a GI project at the Bronx Botanical Garden.
Located in a relatively arid region, Los Angeles only receives approximately 12 inches of stormwater on a yearly basis. Unlike New York City, Los Angeles needs to use its GI to retain water in rain barrels and cisterns for later use. According to Christopher Economides from the Columbia University Water Center, 87% of the city’s water comes from the Los Angeles Aqueduct, from which the city purchases water. The remaining 13% of the city’s water comes from groundwater sources. Having to purchase such a large amount of water deters the city from spending in other essential services, such as education and healthcare. To lower this expenditure and to have better control of their water management, the City of Los Angeles implemented the Standard Urban Stormwater Mitigation Plan, which focuses on pollution reduction from runoff, and The Green Streets program, which promotes GI on the street level to recharge groundwater resources. Los Angeles’ current political climate favors GI implementation efforts, which is not surprising as successful projects serve as evidence of the continued benefits for the city. Successful projects include the Rio De Los Angeles State Park’s constructed wetlands and the South Los Angeles Wetlands Park, which has the capacity to filter 680,000 gallons per day. Despite these successes, the Columbia University Water Center rates the vigor of GI intensiveness in Los Angeles a 5 out of 10, which is a moderate rating on a scale that considers a variety of factors, including whether or not a city has a long term GI agenda, implementation of GI projects, existence of a green roof program, and urban wetlands (see figure 3). However, GI implementation has the potential to become more rigorous in Los Angeles, which would help the city prepare for the 1.7 million person increase in population that the California Department of Finance predicts by 2060. This is a significant increase in population, as it is over one third of the 3.976 million current residents of the city, all of whom will require water.
The City of Los Angeles has the potential to prepare for this heightened water demand. The Community Conservancy International found that approximately 40% of the the stormwater runoff that needs to be cleaned of pollutants could be achieved through GI implementation projects on current public lands. This unrealized potential speaks to the point that the city needs to take a greater leadership role in GI efforts which would help reduce water expenditures, improve water quality, and reduce the urban heat island effect for the whole city.
Figure 2. Wetland in Los Angeles Historic State Park. Photo Credit: Los Angeles State Historic Park.
Unlike Los Angeles., Houston receives a significant amount of rain– 49.8 inches per year. With this amount of rain, intense GI implementation might seem like a given, particularly after the large-scale flooding events brought about by Hurricane Harvey. Organizations like the Conservation Fund and Environment Texas urge Houston to implement GI in order to become more resilient to storm events like Harvey. However, although their ReBuild Houston Program seeks to “improve the quality of life and mobility for residents of the city by rebuilding our drainage and street infrastructure,” it mostly foregoes GI and plans for grey infrastructure. The Houston Stormwater Management Program collaborated with ReBuild Houston to improve stormwater management, yet GI implementation is not a part of the plan. There are other efforts, such as the Clean Waterways organization that generate tools and learning materials to educate the public, however, there is little to no municipal support or involvement for GI implementation or education initiatives. Likely because there are few financial or regulatory incentives to implement GI. A study by Environment Texas found that Houston ranks fourth among the five largest cities in Texas in terms GI policies, fifth being the worst. Los Angeles and New York City have clear collaboration strategies and GI implementation is referenced in a variety of planning tools, such as stormwater management plans and green infrastructure plans– a strategy that would help Houston have a more rigorous GI implementation approach.
However, there are signs that Houston may move toward GI planning and implementation. Plan Houston is a new comprehensive plan that focuses on various physical aspects of the city. According to the the new Plan Houston steering committee, one of their top priorities for the FY 2018 is to “establish a regional approach to detention, including an impact fee based on floor area ratios and/or sectors or watersheds. Some existing parks may be used for detention as well as recreation.” In addition, the steering committee recommends that “more resources should be spent on outreach; it must not be an afterthought. This includes developing a coordinated approach among departments, targeting issues people care about and establishing focus groups to reach more people and get more detailed input.” Both priorities reference the need for GI, collaboration, and community outreach. This language suggests that Houston intends to move forward with improvement of flood management through stormwater detention, but there is still insufficient reference to GI, which certainly needs to play a greater role.
Figure 3. Rating of GI implementation in 11 cities, including New York City, Los Angeles, and Houston.. Photo Credit: Columbia University Water Center.
Successful and widespread GI implementation in a city is dependent upon a variety of factors. A collaborative approach, rather than a fragmented one, is key. Multiple city departments need to be on the same terms when planning for stormwater management and GI implementation. This collaboration, in addition to a high level of political support, as seen in New York City, give cities a good standing to successfully adopt GI on a broader scale.
Feature Image: The Highline in NYC. Photo Credit: Time Out.
Economides, Christopher. “Green Infrastructure: Sustainable Solutions in 11 Cities across the United States.” Columbia University Water Center. (2014): 1-44. Web.
Chau, Haan‐Fawn. “Green Infrastructure for Los Angeles : Addressing Urban Runoff and Water Supply Through Low Impact Development.” (2009): 1–136. Print.
About the Author: Kathia Toledo is a candidate for the master’s in City and Regional Planning at the University of North Carolina at Chapel Hill. There, she is pursuing the Land Use and Environmental Planning Specialization. Kathia is particularly interested in the dynamic between varying urban landscapes, sustainability, and planning. She graduated from UNC-Chapel Hill with a Bachelors of Arts in Geography and Environmental Studies and a minor in Urban Planning. Her hobbies include creative endeavors like urban sketching and photography, biking on the American Tobacco Trail, and exploring new cities and towns.