Openlands Study: Gardens Reduce Flooding and Pollution

December 18, 2014

School and community gardens can be transformative. Their specific power to help manage water in dense urban areas is demonstrated in a new Openlands report, Community-Based Green Infrastructure Solutions: Changing How We Manage Stormwater. The results of the study presented in the report show that both school and community gardens hold and clean rain that otherwise overwhelms sewers and backs up into basements. Gardens also cool the ground temperature in urban heat islands.

In 2012 and 2013, Openlands worked closely with Conservation Design Forum and Gasvoda & Associates, Inc. to monitor, assess, and extrapolate how two school gardens and two community gardens performed in rainstorm events of varying sizes.

The results are striking:

  • A single rain garden installed at Morrill Math and Science School as part of Openlands' Building School Gardens program reduced runoff by more than 90% compared to a nearby parking lot.
  • The redesigned schoolyard at Grissom Elementary (one of four pilot Space to Grow schools completed in 2014) is projected to hold and use all stormwater that falls on the site for about 99% of all storms. No runoff will leave the site. Also, for over 99% of all storms, the green schoolyard will remove virtually 100% of all pollutants.
  • The Global Garden on Lawrence Avenue, part of a 1.5-acre food production garden, prevented almost four times the amount of rain from becoming runoff compared to a neighboring condominium roof. Runoff from the garden was also surprisingly clean, measuring less than detectible limits of almost all of the tested pollutants.
  • Capturing water off a greenhouse roof in cisterns at the Fulton Street Vegetable and Flower Garden prevented 73% of stormwater from draining off site and into the sewer annually.
  • Global Garden, Fulton Community Gardens, and Morrill School rain garden reduced ground temperatures by as much as 54.8°F compared to nearby impervious surfaces.

"Transforming asphalt into green space on school campuses is an exciting win-win for communities," said Openlands Policy Coordinator Stacy Meyers, the report's lead author. "The data we collected shows that rain gardens and other green infrastructure elements built in schoolyards are highly effective at reducing and cleaning stormwater that otherwise overwhelms our sewers and pollutes our waterways. But these gardens and schoolyards also provide great learning spaces for students and create beautiful amenities for neighborhoods that are deficient in park space."

Openlands has long had a commitment to connecting people to nature where they live. In some areas of the City of Chicago, community and school gardens may be the only green space within walking distance of residents. In addition to the ecological and economic benefits these gardens provide, they also hold the promise of changing how people value water and ultimately reconnect to the natural landscape.

The wide-scale transformation of paved and underutilized schoolyards to green spaces is emerging as a national movement. Through the public-private partnership of Space to Grow, Openlands and Healthy Schools Campaign are working with the Metropolitan Water Reclamation District of Greater Chicago, Chicago Public Schools, and the City of Chicago to pool talents and funding to create innovative schoolyards that engage children and their families, reduce flooding, and lower ground temperature in heat island areas. The partners are working together to test new green infrastructure practices to extend the project benefits into surrounding neighborhoods.

The study recommends building upon the successful results of community garden and school garden initiatives to systematically increase the use of green infrastructure throughout the Chicago metropolitan area. By pooling public and private resources, Chicago and other urban areas can stretch limited budgets to reduce flooding, improve water quality, and create healthier, more competitive, sustainable communities.

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