City outlines flood prevention plans as hurricanes intensify and sewer systems face challenges

Posted

As hurricane season nears a close in November, the city aims to refresh residents’ memories on how best to handle the storms and the flooding that often accompanies them. 

The mayor’s office of ethnic and community media and the environmental protection department held a joint meeting on Friday, Oct. 4 to discuss the city’s plan for addressing flooding and hurricanes as they attack New Yorkers with more frequency. 

Department of environmental protection deputy commissioner for public affairs and communications, Beth DeFalco, said, recently the National Oceanic and Atmospheric Administration reclassified the city as a humid subtropical climate, which is surely redundant to anyone who lived through the summer’s weekly warm rainstorms and lack of sunshine. 

The effects of tropical storms have been impacting the city for years. Hurricane Henri hit the city in August 2021, bringing 1.94 inches of rain in an hour. Hurricane Ida dropped 3.15 inches in an hour in September 2021. Most recently, tropical storm Ophelia rained down 2.5 inches in an hour in September 2023. 

As sea levels continue to rise, the effects of the hurricanes that hit the area are only made worse. DeFalco said the biggest problem with rainfall is how fast the water comes down. 

During discussion of hurricanes and rainfall, the conversation often circles back to the sewer system being the cause of the problem, but DeFalco said the sewer isn’t the problem and typically protects the city fully against 98 percent of rain events. 

“Our sewers are working as designed, the problem is they are not designed to handle this amount of rain,” DeFalco said. 

The city’s sewers are built to handle roughly 1.5 to 1.75 inches of rain per hour, but with excessive rainfall, the sewers can become overwhelmed because the water flow becomes greater than the capacity of the pipes. When this backup occurs, water can rise up from manholes, catch basins and basement sewer connections. 

Often the problem with excessive rainfall is combined sewer overflows, a system built into the sewers that is designed to protect the system but often leads to other issues. Combined sewer overflows are triggered when sewers become inundated with water and, with nowhere for the water to go, the flow is rerouted elsewhere.

The Harlem River is one of the locations that water gets rerouted to, meaning a combination of wastewater and freshwater gets dumped into the river when the system becomes overwhelmed. 

The Tibbetts Brook typically enters the sewer system at about 4 to 5 million gallons of water per day and continues to the Wards Island Wastewater Resource Recovery Facility, where the water is filtered for pollutants before being released into the ecosystem. 

DeFalco said flooding can become a problem when heavy rainfall saturates the ground, leaving nowhere for remaining water to go, leading to flooding on streets and often in basements. 

“Water seeks its own level. It will find and travel through cracks in a basement foundation or floor drains,” she said. 

One of the city’s mitigation tactics for flooding includes bluebelts, large-scale natural storage that assists in diverting rainfall away from sewers that also create rich ecological areas. The department of environmental conservation studies maps of the city to find wetlands, streams and areas that naturally collect water. Where possible, these areas are then designated as bluebelts and developed to collect and store water, allowing it to drain into the sewer system at its own pace. 

The department currently manages 545 acres of bluebelts throughout the Bronx, Staten Island and Queens, but is working on bringing the design to all five boroughs.

In the Bronx, the New York Botanical Garden is currently home to a bluebelt system capable of handling 350,000 gallons in one hour. 

Other viable management options include the implementation of porous pavement, which is designed to absorb and drain rainwater. This allows for a paved area to help mitigate excessive rainfall, especially for a city deemed the concrete jungle, where flooding and puddling occur more and more frequently. 

Currently, the department of environmental protection uses this pavement primarily in residential areas and plans to add 10 more miles of the pavement to the Bronx.

Cloudburst infrastructure is another storage management option that can address flooding. The infrastructure captures and holds rainwater and allows it to sit while it waits for the sewer system to recede. The infrastructure requires porous concrete to be installed with a catch basin beneath to collect the rainwater. An area like a basketball court can be designed to hold subsurface storage where the water can be held while it waits.

The city’s hurricane season runs from June through November, but storms typically pick up beginning in August. Regardless, the city has seen its fair share of flooding events in recent years, the kind of events that should call to attention the need for action to combat flooding. 

DeFalco said residents can do their due diligence by having an exit route planned in the event of a flood, as well as knowing the correct evacuation route, which can be located on Maps.NYC.Gov/Hurricane.

One last note DeFalco said may seem inconsequential, but isn’t — there is no such thing as flushable wipes. No matter what the label on a wet wipe says, DeFalco said, all wipes can eventually end up causing clogs and problems later on in the sewer system, making them an undesirable addition to an efficient sewer system. 

hurricane season, city flooding, sewer system, storm preparation, bluebelt systems, porous pavement, tropical storms, flood mitigation, climate change, emergency planning

Comments