College of Engineering

Jacob Rogers

College of Engineering Environmental Engineering

Faculty Mentor: Dr. Franco Montalto Civil, Architectural, & Environmental Engineering

Ziwen Yu Co-Mentor

The Impact of Green Roofs on the Hydrological Response of Urban Rooftops

Because they are impervious, conventional urban roof generate large quantities of stormwater runoff. This runoff enters combined sewer systems and can cause flooding of streets, sewer overflows, and in turn, pollution of surface water bodies. Green roofs are one approach to mitigating these effects, by detaining and evapotranspiring incident precipitation before it flows offsite. This research focuses on a 70m² section of rooftop on the St. Mary’s Recreation Center in Bronx, New York. Its cross section includes a layer of vegetation positioned on top of a growing medium, a water retention layer, and a root barrier. To calculate the effectiveness of this potential solution, a special flume was installed in the drainage system. This flume records depth of runoff flowing through it, and can be converted total runoff through a series of empirically derived equations. By comparing discharge to rainfall, the performance of this green roof was computed. After in depth analysis, the results of this project turned out extremely promising, with each rain event having 20-100% runoff reduction, and a total of 25% decrease in runoff. The long term goal of this research is to show the effects of greenroofs, and encourage others to utilize them.