Why does stormwater infrastructure matter?
|Every year, 27 billion gallons of raw sewage and polluted stormwater flows into New York City’s waterways via combined sewer overflows.
Combined Sewer Overflows (CSOs) happen during and after heavy rains, when New York City’s combined sewer system becomes overloaded. Typical city streets, sidewalks and rooftops are unable to soak up rain the way a more natural landscape might. This rainwater becomes runoff and is diverted into pipes, and then combines with sewage from buildings before being conveyed to the city's wastewater treatment plants. During and after heavy rains, the amount of rain and sewage overwhelms the system and the untreated wastewater is diverted into the nearest creek, river or bay via CSO outfalls like this one on the Bronx River.
CSO on the Bronx River
Combined Sewer Overflow. Diagram: US EPA
H2 Oh No! from the Center for Urban Pedagogy on Vimeo.
What is green infrastructure?
Traditionally, stormwater is managed through hard “grey” infrastructure such as pipes, tanks, and water treatment plants. Green infrastructure keeps stormwater out of the sewer system and is a way to manage stormwater onsite, creating a healthier watershed. Examples include bioswales, green roofs, rain gardens, enhanced tree pits, rain barrels, and permeable pavement. Additional benefits include increased neighborhood green space, biodiversity restoration via the creation of additional habitat, natural filtration of pollutants, carbon sequestration, cleaner air, and cooler temperatures.
Green street, improved tree pit - Stratford Ave
| Rainwater barrel - private home within Bronx River watershed
|| Bioswale - Shoelace Park 213th to 211th Street
A green street in the Bronx River sewershed. Photo: Earth Institute, Columbia University.
Who is involved in the Bronx River watershed?
What progress has been made?
This project involves multiple actors, including various city agencies, academic institutions, community organizations, and private homeowners.
The NYC Department of Environmental Protection (DEP) has made stormwater management via green infrastructure one of their primary goals. Their Green Infrastructure Plan includes the Bronx River as one of its twelve priority sewersheds . The Green Infrastructure Program, which converts unused spaces within the right-of-way, such as vacant traffic islands and medians, into rain gardens, is an interagency collaboration between the Department of Transportation, the Department of Parks and Recreation, and the DEP. The New York City Soil and Water Conservation District also lends tremendous support for green infrastructure projects in the Bronx and organizes educational tours. A team from Columbia University headed by Patricia Culligan is researching the effectiveness of the city’s efforts and collecting information regarding best practices. Sustainable stormwater management practices are featured prominently in several of the Alliance’s plans, such as the watershed management plan, greenway plan, and ecological restoration and management plan.
A map of green infrastructure in the Bronx River watershed can be viewed here.
S.W.I.M. (Storm Water Infrastructure Matters) Coalition:
Google map of green infrastructure in the Bronx:
Map of green infrastructure in New York City, DEP:
"I love the Bronx: Bioswales"
“Just How Effective is Green Infrastructure?” The Earth Institute at Columbia University, Blog:
NYC Green Infrastructure Plan and Annual reports (Bronx River spotlight p. 74-77):