Flood Prevention


Historically, some communities throughout New York City have been prone to flooding. Sections of Queens, Staten Island, the Bronx and Brooklyn, for instance, have periodically faced this problem. In recent years, however, flooding has occurred more frequently than in the past, affecting a broader range of communities than ever. Local topography, including lengthy river and ocean coastlines, dense urban development patterns, the capacity of our aging sewer system and increasingly extreme weather are some of the biggest causes.

To learn about what to do during or after a flood, visit NYC Emergency Management.

Causes of Flooding

Extreme Weather and Climate Change

New York City faces increasing risks from the impacts of global climate change. In 2015, the NYC Panel on Climate Change (NPCC) released updated projections for the region in its publication Building the Knowledge Base for Climate Resiliency. According to its findings, by 2050, NYC will experience:

  • Increased average temperatures (4.1 to 5.7° F)
  • Increased precipitation (4 to 11 percent)
  • Rising sea levels (11 to 21 inches)
  • Increased frequency and intensity of coastal flooding
  • Average number of days above 90°F is expected to at least double
  • Increased frequency and intensity of hurricanes across the North Atlantic Basin

Increased Precipitation

New York City experiences significant precipitation throughout the year, with relatively little variation from month to month in a typical year. Annual average precipitation ranges between approximately 43 and 50 inches, depending on the location within the City. Precipitation has increased at a rate of approximately 0.8 inches per decade from 1900 to 2013 in Central Park. Such changes in climate patterns may result in more frequent localized flooding over time.

Sea Level Rise and Tidal Impacts

In coastal areas, rising sea levels can exacerbate local flooding conditions, causing tidal water to enter the sewer system and reducing the speed at which water can drain from inland sources. Sea level rise in New York City has averaged 1.2 inches per decade since 1900, nearly twice the observed global rate.

Learn more about our Climate Resiliency programs and intiatives.

Blocked Catch Basin Grates

Partially clogged catch basin
Partially Clogged Catch Basin
Fully clogged catch basin
Fully Clogged Catch Basin

Another serious cause of flooding is blocked catch basin grates in our streets. This occurs when rain water—especially during very intense storms—pours over streets and sidewalks, pushing debris like leaves and litter on to the catch basin where it molds itself into a mat. Such debris can block the grate so completely that the rain water cannot enter the storm sewer. Instead, it pools around the basin, causing flooding even before the storm sewer is full.

If you observe a catch basin that is clogged or in need of repair, please call 311 or fill in this online this form so our staff can track, pin point, and address any problem areas.

Surcharged Sewers

Illustration of the causes of sewer backups and street flooding
Causes of Street Flooding and Sewer Backups

Sewers can also become overtaxed during intense rain events when the sheer volume of stormwater and wastewater entering the system fills them to capacity, leaving no space for excess water to enter. In this condition, described as a sewer being surcharged, the excess stormwater remains above ground. Unless absorbed by green spaces or channeled to a body of water, this flooding can flow off the street into below-grade areas such as driveways, patios and basements.

Day to day, we work to keep our sewer system up and running efficiently. We clean and maintain our sewer and drainage systems to keep them in a state of good repair. At the same time, we plan and build both traditional infrastructure and implement best management practices for managing stormwater and wastewater.

Sewer Backups

If you have experienced a sewer backup after a heavy rain event or snow melt, call 311 or fill in this online form. For information about how to clean a home after a flood or sewage overflow, visit Sewer Backup or Flood Clean Up.

What You Can Do to Help Prevent Flooding

There’s actually a lot New Yorkers can do to protect our City from flooding. For additional tips to prevent your home from flooding, download our Homeowner’s Guide to Rain Event Preparedness.

Clean Your Nearest Catch Basin

We do our best to keep catch basins clear of debris—but all New Yorkers can chip in. Pick up your leaves for collection each fall. Check guidelines and dates of the Department of Sanitation’s free Leaf Collection Program.

You can also remove litter, leaves or other debris from the grates of a catch basin to help it function at its best. Learn more about why litter on our street can become Trash in Waterways.

If you see a catch basin that is clogged or damaged, please call 311 or fill in this online form so that we can follow up.

Conserve Water

One way to reduce pressure on overburdened sewers is to use less water in our homes and businesses. The less water we use, the less sanitary flow we create, and the more space there will be for stormwater in our sewers during heavy storms. Reducing the water we use also has the added benefit of curbing greenhouse gas emissions. The less water we let go down the drain or flush down the toilet (we call it “wastewater”), the less energy it takes for the City’s 14 wastewater treatment plants to process and treat it.

Treat our Sewer System with Care

Though our sewer and wastewater treatment system seems like a technical process, there are lots of things each of us can do to help maintain a healthy sewer system. What you pour down the sink, flush down the toilet, or leave at the curb can make a big difference in how well our sewer system functions.

Become a Rain Garden Steward

Rain gardens can improve your street by reducing ponding, providing summer shade, and greening your community. Most importantly, rain gardens improve the environment by allowing rain to be naturally absorbed into the ground instead of flowing into the sewer system. We have successfully built thousands of Green Infrastructure installations, like rain gardens, across New York City.

If you would like to learn more about our rain garden steward program, visit Become a Rain Garden Steward.

The City’s Climate Change Program

Local government is leading the way in addressing the many challenges we’re likely to face as global warming intensifies. In accordance with the New York City Mayor’s Office, we have developed a comprehensive Climate Resiliency program. The program requires that planning and development take into account and respond to climate-change related risks. It calls specifically for planning, engineering and design processes that will help make our systems more resilient to flooding, today and tomorrow.