This winter, we’ve seen an unprecedented amount of rain in the Bay Area. Since we are normally in drought conditions, I am often thinking about how cities can conserve the limited freshwater resources we have. However, all this rain has turned my attention to a just as important urban infrastructural topic: stormwater runoff. So let’s talk about it.
I was walking with my friend, talking about all this rain, and as I was explaining all the impacts of the increased rainfall I told her “You know, at the end of the day, it’s all about stormwater management”. This quote cracked us both up, but it rings true.
When we develop urban areas, we often increase the amount of impervious surface (think concrete jungle). These impervious surfaces include households and commercial areas that create waste, roads that collect exhaust, oil, and other car debris, and industrial facilities that sometimes release their chemical waste. The EPA estimates that the average city block generates more than 5x as much runoff than a forested surface of the same size. After a heavy rainfall, all this debris flows through the city into our waterways and causes a variety of issues downstream.
One issue is flooding. Who hasn’t heard about a friend, family member, or friend of a family member whose house or yard was flooded due to these rains? Due to the topography of the East Bay and San Francisco, flooding after heavy rainfall is actually quite common as water comes rushing down the hills, flows through creeks that run towards the bay, and pools in the flatlands if not properly drained. Additionally, when a storm drain gets clogged by debris, water continues to collect and flood the streets. Not only does flooding cause further infrastructural damage and transportation networks, it concentrates polluted runoff in certain areas
Another issue is water pollution and sewage overflows. In most of the Bay, gutters send runoff right into creeks that lead out into the bay without any treatment. This is already an issue as it leads to increased amounts of pollution into the Bay. San Francisco, on the other hand, has a combined sewer system where runoff goes into the sewer system to be treated before being released in the bay. For either system, a heavy surge of rainfall and stormwater runoff can overwhelm the underground pipes and lead to an overflow in which both the stormwater and sewage must be dumped into waterways. This past December, the Bay Area had to release 62 million gallons of raw or partially treated sewage into creeks, estuaries, and the bay.
Stormwater runoff connects us all, as water and debris from one person’s lot will impact a neighbor downstream whether it be on their flooded street corner, their eroded landscaping, or their polluted shoreline.
So how can we work to ameliorate this issue? Would it be a Sustainable Communities blog post if I didn’t suggest green infrastructure? Green Infrastructure uses the ecosystem services of water absorbent soils, plants, trees, and wetlands to reduce bursts of stormwater runoff and protect and mimic the natural water cycle. There are lots of different ways you can incorporate green infrastructure into urban design depending on different community needs. My favorite are Bioswales – rain gardens placed next to sidewalks or in medians along the road. They bring greenery to the street, promote pollinator friendly planting, and help absorb water where it typically concentrates and floods. You can see cool examples of these in Berkeley! One close to campus at the corner of Hearst and Oxford (Figure 1,2), and another on Spruce and Vine (Figure 3,4).
Sustainable Communities 
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