It’s raining. It’s pouring. We’re flooding.

Flooding. There is something about water coming into your house that is so…invasive.  And when it comes in as bacteria carrying storm water from a sewer system, it is that much more upsetting and expensive.  Now multiply that equation by 181,000 (the number claims of property damage from flooding in the Chicagoland area over the last 5 years), and you have yourself a $773 million situation.  This is the situation that the City Digital Smart Green Infrastructure Monitoring project was designed to address.  Let me explain how we got here.

Sewer systems in major cities across the US and around the world often times are a century or more old.  Chicago built ours in 1856, as a combined system (carrying wastewater and stormwater together, away from people and homes and toward treatment plants).  And while the city spends approximately $50 million per year to clean and modernize the sewer lines and related structures, it is still a system built on notions of water events prior to our knowledge and understanding of climate change.  

Climate change has altered the behavior of water events.  As an example, storms are now more intense, shorter in duration, and more localized than they were 100 years ago.  This taxes the sewer systems in various locations around the city during times of intense rainfall.

In addition, there is far less green space in the city than there was 100 years ago.  Green spaces soak up stormwater.  The soil, and native plants living in it, utilizes that water and naturally cleanses some of the runoff.  When we build streets, roadways, parking lots, and buildings, we replace that green space with something impermeable.  Streets and rooftops, are like man-made rivers – they take stormwater and send it into the sewer system.  More hard surfaces + less green space = more water going into the sewers.

For years, we have known that adding “green elements” to the built environment diverts water from the sewers and puts it back into the natural system.  Rain gardens, rain barrels, cisterns, and permeable pavers are all natural elements that act to ultimately get more water back into the ground, less into the sewer system.  What we haven’t known is:

  • How much water is diverted from the sewer system?
  • Which green elements work best in which locations and under which conditions?
  • What is the quality of the water once it goes through the natural system?

Enter the world of sensors and data.  The Smart Green Infrastructure Monitoring project was one of the first projects to use the City of Chicago as a test bed for experimentation at scale.  In this case, we used the city to test a water monitoring solution that could scale to multiple cities around the globe.  City Digital selected multiple locations around Chicago to place sensors in different “green elements” to understand how they reduce the impact of flooding.  As an example of one such green element, in Chicago’s Uptown neighborhood, we incorporated permeable pavers (instead of impermeable asphalt) into a street scape system, which itself was part of a broader City project to create a shared plaza.  We added sensors beneath the pavers to determine how much water was absorbed into the ground (utilizing expertise from engineering company AECOM, and University of Illinois based-startup, Senformatics), and thereby diverted from the sewer system.  

optiOn Goose Island (where UI LABS is located), we built a bioswale with native plants. Working like rain gardens, bioswales are areas at the bottom of a sloped landscape filled with native vegetation to drain runoff water and remove pollution.   Again, sensors were added to determine the amount of water absorbed into the ground, water that otherwise would have been diverted to a sewer.  And other locations in the city will have other types of elements, and sensors to gather data on their performance.

Once the sensors pick up this data, it is collected in the Azure cloud.  There, it is city-digital_dashcombined with other data sources (such as weather forecasts) and is prepared for visualization on a dashboard through our Azure partner Opti, who focuses on new technology approaches to managing stormwater.  Over time, the data collection and analysis will also include metrics on the quality of the water as it passes through a natural system, allowing us to understand how runoff is handled.  Bringing all of this distributed data together will enable insights that a city can use as it plans for capital improvements.  

Imagine if every time a city made plans for street surfaces, parks, streetscapes, or the water system itself, it had the data to understand how to best leverage the opportunity to add green infrastructure.  Further, it would have insights as to which types of green infrastructure would work best in various locations.  Of course, we plan on extending type of experimentation to other water issues, but that is a blog for another time.   For more information on Smart Green Infrastructure Monitoring and other City Digital projects, go to http://www.citydigital.org/focusareas-1/.

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