Where Can Green Roofs Reduce Combined Sewer Overflows in the Bronx?

Rutgers University

The Bronx, New York, like many older urban areas in the United States, suffers from the negative environmental impacts from combined sewer overflows (CSOs). Green roofs have been proposed as a best management practice to reduce storm water runoff and CSOs. These vegetated roof tops can detain rainfall along with providing other benefits to the building owner and community.

This map summarizes the results of the master’s thesis, “A Geographic Approach to Modeling the Impact of Green Roofs on Combined Sewer Overflows in the Bronx,” submitted to Rutgers University graduate program in geography.

Building-level geographic data was used to estimate the potential area for green roof implementation in each sewer system subcatchment. A software program was designed as a decision support system with a green roof micromodel, a simple sewer system model, and an interactive map. The model results show that if extensive green roofs were implemented on all available flat roof space, annual CSOs could be reduced by over 30 percent. The model results displayed here show geographic variation in the magnitude of the response and in the effectiveness of green roofs as a CSO best management practice.

Courtesy of Danielle Hartman.

Map Book Page [PDF]