Part 5 – How Green Infrastructure is a Sustainable Solution

To wrap up this series on green infrastructure, we will investigate how the services green infrastructure provide fit into the concept of sustainability. At its most basic, sustainability means to provide for the needs of today, whatever those needs may be, without compromising the ability of the future generations to meet their needs. In order to be successful must adequately address three broad topics, often referred to as the pillars of sustainability: environment, society, and economy. If a program does not address its’ environmental impact, then it compromises future generations by degrading environmental quality. If it does not provide societies needs, then the project cannot work long term as the people will search for an alternate method that does meet their needs. If it is not economically viable then the project will not have sufficient resources and support to continue.

We will now look at how green infrastructure in cities can be used to provide a sustainable solution to stormwater management in terms of the three following questions: is it good for the environment? Is it good for society? Is it good for the economy?

Environment

As we have discussed up to this point, green infrastructure works by reducing the amount of impervious surface and, consequently, reducing runoff. This reduction in runoff has multiple benefits to the environment previously discussed, including reducing the total number of sewer overflow events, reducing loading of pollutants such as heavy metals, pesticides, and nutrients to our waterways, reducing erosion caused by urban stream syndrome, improving wildlife habitat, and improving groundwater recharge. Compared to gray infrastructure solutions, it is clear that green infrastructure provides more environmental benefits.

Society

In talking about how green infrastructure is good for society, we will look at two broad categories; one, how well does green infrastructure perform compared to gray infrastructure (i.e. can green infrastructure alone meet our demand for stormwater control), and two, what other benefits does green infrastructure give to society. In order for green infrastructure to be a solution, it must meet society’s need for flood control. As such it is unrealistic to assume green infrastructure can, overnight, replace gray infrastructure in major cities, but it is not necessary to eliminate gray infrastructure altogether. The pipes are in place and there is no reason pull them out and render them useless in the name of a green infrastructure plan. Instead green infrastructure can be added gradually to reduce the load on our gray systems, and we can hope, with persistence and time, that little rainwater will make it to these systems and overflows can be a thing of the past. The City of Philadelphia serves as an inspiration to this strategy by committing $1.6 billion to green infrastructure for runoff control (Madden, 2010).

In addition to meeting our need for flood control, green infrastructure can also provide important social benefits. Trees and other greenspaces in cities tend to improve quality of life, be it from aesthetic beauty, higher property values, improved air quality, protection from urban heat island, etc. (Wolf, 2003). Parks can promote recreation and more active lifestyles for nearby residents (Arnberger & Eder, 2012), community gardens can not only provide food and entertainment for the individual but can open up social connections, potentially improving neighborhood cohesion (Egli et al., 2016). Compared to traditional gray infrastructure techniques, which most people do not notice and only impact the individual’s life when the systems fail, it is clear green infrastructure has more to offer the people of cities.

Economic

The main reason for the slow adoption of green infrastructure by cities are the higher upfront costs of implementing green infrastructure as opposed to traditional methods, and the general hesitation most government systems have to change. Indeed, permeable pavers are much more expensive than asphalt per ft2 for example, and the high cost of implementation can dissuade people. However, infrastructure is meant to be seen as an investment; the need for flood control will not go away and so our means of controlling it should be forward-thinking and future oriented. Rather than looking at the initial price tag of implementation and construction, infrastructure should be assessed based on total lifetime benefits (Jayasooriya & Ng, 2014). When assessing the total lifetime benefits of a green infrastructure project, it is important to account for all benefits the project will provide, such as energy savings from decreased water treatment requirements or heating requirements, air and water pollutant reduction, reduced carbon footprint, reduced erosion and sedimentation, etc. (Spatari et al., 2011; De Sousa, et al., 2012). When accounting for these secondary benefits, though results will vary depending on the quality of individual project design, most green infrastructure projects are more cost effective long-term than gray infrastructure counterparts (Wang et al., 2013; EPA, 2013).

Conclusions

Throughout this series we have investigated the root causes and problems with urban stormwater, and how gray infrastructure is not suitable to address these concerns. As cities expand, so does the amount of impervious surface, increasing the runoff issue. Under heavy rain events with unsuitable infrastructure, sewer systems are inundated with stormwater, leading to overflows. These overflows have a number of environmental and public health risks. It is clear this is not the route to a sustainable future, as it leads to environmental degradation, public health risks, and high maintenance costs. Green infrastructure, on the other hand, offers a number of benefits to the environment and the people, reducing runoff potential and pollutant loads. Many green infrastructure strategies, when designed well, provide better long-term economic benefits from reducing operation and maintenance costs, reducing emissions, reducing energy requirements, and/or providing ecological services. Green infrastructure, therefore, represents a more sustainable route cities can take when planning their stormwater infrastructure.

References:

Arnberger, A. & Renate Eder. 2012. The influence of green space on community attachment of urban and suburban residents. Urban Forestry & Urban Greening, 11(1), 41-49.

De Souse, M., Mantalto, F., & Spatari, S. 2012. Using life cycle assessments to evaluate green and grey combines sewer overflow control strategies. Journal of Industrial Ecology, 16(6), 901-913.

Egli, V., Oliver, M., & Tautolo, E. 2016. The development of a model of community garden benefits to wellbeing. Preventive Medicine Reports, 3, 348-352.

Environmental Protection Agency. 2013. Case Studies Analyzing the Economic Benefits of Low Impact Development and Green Infrastructure Programs. Retrieved from: https://www.epa.gov/sites/production/files/2015-10/documents/lid-gi-programs_report_8- 6-13_combined.pdf on 04/16/2019.

Jayasooriya, V. & Ng, A. 2014. Tools for modeling of stormwater management and economics of green infrastructure practices: a review. Water, Air, & Soil Pollution, 225, 2054-2068.

Madden, S. 2010. Choosing green over gray: Philadelphia’s innovative stormwater infrastructure plan. Master’s Thesis, Massachusetts Institute of Technology Department of Urban Studies and Planning. Retrieved from: https://dspace.mit.edu/bitstream/handle/1721.1/59750/670433292- MIT.pdf?sequence=2&isAllowed=y on 04/16/2019.

Spatari, S., Yu, Z., & Montalto, F. 2011. Life cycle implications of urban green infrastructure. Environmental Pollution, 159(8), 2174-2179.

Wang, R., Eckelman, M., & Zimmerman, J. 2013. Consequential environmental and economic life cycle assessment of green and gray stormwater infrastructures for combines sewer systems. Environmental Science & Technology, 47(19), 11189-11198.

Wolf, K. 2003. Ergonomics of the city: Green infrastructure and social benefits. Engineering Green: Proceedings of the 11th National Urban Forest Conference. Washington D.C.