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Stormwater

Stormwater is generated from rain and melting snow which is conveyed over impervious surfaces such as rooftops, streets, and sidewalks.  Rather than being absorbed into the ground, much of the stormwater in New York City flows over impervious surfaces into roof drains or catch basins in the streets, and from there into the sewers.  These impervious surfaces cover approximately 72% of New York City’s 305 square miles in land area and generate a significant amount of stormwater.  Stormwater can pose challenges to the City in the form of combined sewer overflows and flooding.  This section describes how stormwater is conveyed through the City, the challenges it creates, and what the City is doing overcome them.





NYC Green Infrastructure Program
New York City’s Green Infrastructure Program is a multiagency effort to design, construct and maintain sustainable stormwater management practices throughout New York City.
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DEP

Types of Sewer Drainage Areas in New York City
In New York City, stormwater is conveyed through combined sewers or separate sewer systems. In unsewered areas, water flows directly over the ground into waterways.
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Combined Sewer Overflows (CSOs)
Sometimes, during heavy rain and snow storms, combined sewers receive higher than normal flows. Treatment plants are unable to handle flows that are more than twice design capacity and when this occurs, a mix of excess stormwater and untreated wastewater discharges directly into the City’s waterways at certain outfalls. This is called a combined sewer overflow (CSO). We are concerned about CSOs because of their effect on water quality and recreational uses.
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Flooding

Flooding in New York City
A look at the areas prone to flooding, the causes of flooding in New York City, and what residents can do to help protect our City from flooding.
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Rain Barrel Giveaway Program
As part of its citywide effort to reduce stormwater runoff and create a more livable, sustainable city, DEP initiated the Rain Barrel Giveaway Program. Rain barrels capture stormwater from your roof and store it for future use such as watering your lawn or garden.
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The Staten Island Bluebelt
The Staten Island Bluebelt is an award winning, ecologically sound and cost-effective storm water management for approximately one third of Staten Island’s land area. The program preserves natural drainage corridors, called Bluebelts, including streams, ponds, and other wetland areas.
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Guidelines for the Design and Construction of Stormwater Management Systems
DEP has published Guidelines for the Design and Construction of Stormwater Management Systems.
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Green Infrastructure