Part 1 – Stormwater is Like Traffic

In this series I will investigate green infrastructure and its use in stormwater management. Before we can begin, it is important to understand what “stormwater management” and “green infrastructure” mean and why they are important concepts for city planners. Later posts in this series will dive deeper into the reasons we need stormwater management and what it looks like in America. Briefly though, we can think about stormwater in terms of a more concrete infrastructure issue, traffic.

Stormwater Management & Traffic

We know as cities grow, more and more people move in with more and more cars and more and more places to drive to. We see this in our longer commutes to work, busier parking lots at the grocery store, more back-ups and accidents on the freeways, etc. It is a sign that we can see and feel telling us that our city is growing. While we may not notice it, there is a great deal of behind-the-scenes planning that goes into this kind of expansion, with city planners designing traffic signals and stop signs to new roads and freeways in an attempt to direct cars where and when to go in a way that reduces “traffic” as efficiently as possible. However, even with all this design and planning, we can still sit in bumper-to-bumper traffic five days out of the week and wonder “Is there a better way?”.

By now you are probably wondering how this tangent on city traffic could possibly relate back to rainy weather and where all the water goes. Well, car traffic and rainwater actually function in fairly similar ways. They both represent inputs that ebb and flow but that require permanent infrastructure for cities to function properly. For example, there may be almost no cars on a back road at 3:00 AM, but that doesn’t mean you could or should somehow get rid of that road during that time. Similarly, there may be weeks or months at a time when rainfall is almost non-existent, but it would be just as ridiculous to suggest eliminating sewer grates during this time, because if it did rain you would be subject to severe flooding. If we can accept that planning is required to build proper infrastructure (roads, lights, and signs) to direct cars where to go to avoid massive traffic problems, then it follows suit that we must also plan and use infrastructure to direct water where to go to avoid massive flooding problems.

Gray vs. Green Infrastructure

In keeping with the traffic metaphor, we can now think about green infrastructure as an answer to the question “Is there a better way?”. For traffic the better way may be to restrict the number of cars on the road and invest heavily in making public transit more efficient, cost-effective, and accessible. This would help solve the problem of having too many cars on the road and have the added environmental benefits of reducing air pollution and greenhouse gas emissions (Stevanovic et al., 2009). For stormwater control, the better way may be investing in green infrastructure over gray infrastructure; but what is gray infrastructure?

Traditional or “gray” infrastructure represents the concrete, asphalt, brick, steel, etc. that we build in a city to accommodate the multifaceted needs of its people. For education this includes school buildings, for healthcare this includes hospitals, for electricity this includes power plants and power lines, for clean water this includes water treatment centers and underground pipes, and so on and so forth.

When it comes to stormwater management, the gray infrastructure “solutions” include gutters and underground concrete channels to direct water out of the streets as quickly as possible (Kerkez et al., 2016). In the next post we will see the environmental and public health consequences of this type of system but suffice it to say that millions of gallons of stormwater rushing to our cities’ sewer systems and water bodies during rain events can have some nasty outcomes. Building more gutters and channels to relieve overflows is like building bigger freeways to relieve traffic congestion; it is treating a symptom rather than a problem, and even then only makes the symptoms worse as larger freeways have been shown to consistently increase traffic problems, known as the induced travel effect (Milam et al., 2017).

So what does green infrastructure do? Instead of using manmade materials to meet our needs, green infrastructure utilizes nature to do so. In the stormwater context this includes using vegetation and/or exposed soil to capture water and prevent some or all of it from entering the sewer system in the first place, similar to the technique of limiting cars on the road, thus addressing the problems rather than the symptoms (Wise, 2008). We will look at different strategies to apply green infrastructure and for stormwater management and what they look like in part four of this series.

Moving Forward

So far, we have briefly discussed what stormwater is, why it is important to plan for it, and the differences between gray and green infrastructure in general and in terms of stormwater management. The rest of this series will dive deeper into each of these areas, starting with the reasons cities have more issues with rain and stormwater compared to rural areas, looking at the history of gray infrastructure approaches to stormwater management in America, providing concrete examples of what some common forms of green infrastructure solutions look like, and concluding that green infrastructure is a sustainable solution for stormwater management that addresses environmental concerns, is socially acceptable, and is economically viable for cities across the world.

References:

Kerkez, B., Gruden, C., Lewis, M., Montestruque, L., Quigley, M., Wong, B., Bedig, A., Kertesz, R., Braun, T., Cadwalader, O., Poresky, A., & Pak, C. 2016. Smarter Stormwater Systems. Environmental Science and Technology, 50, 7267-7273.

Milam, R., Birnbaum, M., Ganson, C., Handy, S., & Walters, J. 2017. Closing the Induced Travel Gap Between Research and Practice. Journal of the Transportation Research Board, 2653(1), 10-16.

Stevanovic, A., Stevanovic, J., Zhang, K., & Batterman, S. 2009. Optimizing Traffic Control to Reduce Fuel Consumption and Vehicular Emissions: Integrated Approach with VISSIM, CMEM, and VISGAOST. Journal of the Transportation Research Board, 2128(1), 105- 113.

Wise, S. 2008. Green Infrastructure Rising. Planning, 74(8), 14-19.