A Soaked Solution to Storms

New York City’s climate adaptation plan looks to sponge-like surfaces to fight heavy rainfall.

By Chloe Bennett

October 28, 2022

Alex Dukhanov on Unsplash

Permeable pavement, spongey basketball courts and underground water basins are just some of the super soppers set to be installed around New York City in the next three years to tackle expected increased flooding from climate change.

The changes to the urban landscape are part of the city Department of Environmental Protection’s Cloudburst Management plan, which maps out green infrastructure developments, including how to transform part of the cityscape into porous surfaces that can absorb and store rainwater.

Though there isn’t a silver bullet, porous pavement that can help keep the city cool through evaporation is key to climate adaptation, Pablo Herreros Cantis, a research fellow at the New School’s Urban Systems Lab said.

Cloudbursts, short periods of heavy rain that are usually contained to one neighborhood or town, are becoming more common globally amid the climate crisis. In September 2021, remnants of Hurricane Ida released a deadly cloudburst that unleashed three inches of rain in one hour in New York — the same amount the city usually receives in April, traditionally its wettest month.

The plan arrived just over a month before the recent 10th anniversary of Superstorm Sandy, which destroyed hundreds of homes and killed 44 New Yorkers. Although hurricanes and cloudbursts are different, both massive rainfalls and the kind of storm surge Sandy brought are expected to bring more flooding in the years to come.

When large amounts of rainfall quickly, the water cascades down paved streets into rivers, often overwhelming sewage pipes and flooding basements. At least 11 people were found dead in New York City basements in Ida’s wake. Untreated wastewater can also show up in people’s homes and businesses, potentially spreading cholera and other diseases.

Superstorm Sandy’s 14-foot surge halted operations at six New York city wastewater plants by flooding the city’s sewer systems. Some 11 billion gallons of partially or completely untreated sewage flowed into city streets and homes during the days following the storm. Under the city’s cloudburst plan, federal and municipal funds would be used for sewer upgrades and other measures, though it’s unclear what the project will cost.

The city’s cloudburst infrastructure plan is already in place in Queens and the Bronx, with 17,000 linear feet of porous pavement installed in roadways. In Brooklyn and the Bronx, an additional 300,000 linear feet is entering the design process. A sunken basketball court that would collect and store rainwater using porous pavement is on tap for the South Jamaica Houses in Queens.

A similar project will be designed for East Harlem’s Clinton Houses, which are at risk of flooding because of the area’s low elevation. Also planned in the Bronx: daylighting, which involves removing any obstructions to streams that flow underground streams.

Green infrastructure, including the kinds contained in the cloudburst plan, can be effective in preventing sewer overflow, said Herreros Cantis.

But the measures need to be scaled to the right size for the area and intended purpose, Herreros Cantis noted. Small-scale solutions, like rain gardens that absorb water, are useful for normal rainfall. Storms and cloudbursts require bigger infrastructure. In other words, some of the infrastructure needed to reduce sewer overflow still often isn’t big enough to handle a cloudburst.

“It can be done with green infrastructure, but it still needs way larger interventions, much more space, much more storage capacity,” Herreros Cantis said.

Scaling up green infrastructure is what Brooklyn College professor Jennifer Cherrier set out to do when designing ecoWEIR, an underground storage tank for rainwater. Water flows into the system, where it’s filtered and monitored by a sensor.

The system is already in use in Prospect Park, just a few feet beneath the grass and soil near Dog Beach. Two 600-square-foot tanks were installed in April 2021 to prevent algae growth in Prospect Park Lake by filtering out phosphates.

“You can’t remediate a lake like that until you stop putting the pollutants in, it’s like turning it off at the tap,” Cherrier said.

Phosphate keeps metal pipes from dissolving and is not harmful in small amounts. But it can lead to algal blooms, which are toxic to humans and wildlife. “It’s not a bad amount, but we’ve been adding one milligram of phosphate to the water since 1990, so it’s additive,” Cherrier said.

Cherrier said one of ecoWEIR’s strengths is that it’s customizable to its surroundings. The sensor valve system can be integrated into several types of green infrastructure, such as green roofs, plazas and streets. It also has the potential to store water that can be recycled for various purposes.

But to combat flooding caused by cloudbursts, the system would have to be scaled up. It’s achievable, but a project of that size would require a large sum of money and the installation process could take up to 20 years, Cherrier said.

But that doesn’t mean it’s not worth the wait. After all, part of what inspired Cherrier to design ecoWEIR in the first place was the draw of creating a solution.

“I decided to crawl up on land and start to look for solutions to address human impacts to coastal systems, because quite frankly I was just really getting depressed, with the rest of society, with cataloging all the problems,” she said.