Case Study

Public Safety

Philadelphia: A Water Department Reduces Crime


Photo credit Philadelphia Water Department

Philadelphia wanted to expand green infrastructure to reduce stormwater pollution. They did not expect that it would also decrease crime rates.

Philadelphia, PA

Warm and humid summers, mild fall and spring, cold winters


42.2% African American, 36.9% White, 12.3% Hispanic, 6.3% Asian, 2.3% Other

The Philadelphia Water Department introduced their Green City, Clean Waters program in June 2011 in an attempt to reduce the amount of water entering the combined sewer system. During large storms, the combined sewer system would overflow and cause the pollutants to enter the city’s surrounding waterways. To fix the problem, the Philadelphia Water Department began to build up the city’s green infrastructure, and unintentionally reduced crime rates at the same time.

Since the project was started, over 1,100 green stormwater infrastructure tools have been implemented, including stormwater planters and porous pavement. Green City, Clean Waters predicts that by the time they finish greening the city, they will have reduced the amount of water reaching the sewer system by 85 percent.

A greener city is not the only benefit, though. A study done by a team of researchers with the U.S. Forest Service compared the neighborhoods that had received greening treatments and with control sites, which were still barren. The study found that crime in general decreased, but the most significant decrease was seen in the number of narcotics-related crimes around the treated sites. Throughout the duration of the study, Philadelphia’s city-wide drug-related crimes increased by 65 percent, but the rates around the greened areas fell 18 to 27 percent.The Impact of Green Stormwater Infrastructure Installation on Surrounding Health and Safety

The conclusion drawn by researchers for the drop in narcotics-related crimes is that activated green spaces convey the idea that these are no longer anonymous areas. Trees and parks need to be looked after, and in the case of Philadelphia, this is generally done by a government official. In addition, members of the public are more likely to spend time in green spaces, further deterring crime from occurring in those neighborhoods.


Green City, Clean Waters is a 25 year, $2 billion initiative.


For more information, please visit Philadelphia Water Department’s Philly Watersheds site.


  • Philadelphia Water Department
  • U.S. Environmental Protection Agency
  • The U.S.-Brazil Joint Initiative on Urban Sustainability
Lessons Learned
  • Vacant and abandoned spaces are more susceptible to crime
  • Random, not scheduled, maintenance on the green infrastructure helped to prevent crimes from happening near those sites.
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