Landmark Green-Wood Cemetery Has a New Job: Protecting Brooklyn From Flooding

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Graves aren’t the only things underground at Green-Wood Cemetery in Brooklyn. Also buried: a new system for storing water to prevent flooding when it rains.

Massive tanks lie underneath a storage yard for trucks and lawn equipment —  waiting to hold rainfall to avoid stressing area sewers, which become inundated during downpours.

Elsewhere, the cemetery has two other projects to keep flooding at bay, newly installed this summer: roadway pavers that absorb rain, and a pond that now drains into the city sewer system before storms to make room to hold more water.

Green-Wood’s government-funded $2.6 million in stormwater-management projects are part of a wave of efforts by private property owners around the five boroughs to manage increasingly frequent and intense rainstorms by turning their land into a sponge.

The stakes of such projects to increase absorption and deal with torrential rainfall are clear in the aftermath of Hurricane Helene, which barrelled down in the southeastern United States and left a path of destruction in its wake — including over 100 deaths, power outages and widespread flooding. Though a project like Green-Wood’s may not make a huge difference in such a storm, it is one part of a broader effort to handle the kind of severe rainstorms that are becoming more common.

The city Department of Environmental Protection, which runs the city sewer system, provided some of Green-Wood’s funding as part of a $53 million grant program to seed dozens of such efforts, including at a church in Staten Island and in the yard of a construction supply company in Queens. The state Environmental Facilities Corporation covered the rest.

Most of the city’s sewers handle both stormwater and wastewater, and heavy rain can overwhelm the system. When that happens, raw sewage spills into creeks and rivers in what’s known as a combined sewer overflow. In especially intense storms, the dirty sludge backs up into people’s homes and businesses, causing property damage and threatening lives — as in the storm Ida, which killed at least 13 New Yorkers.

A storm last September led to the Fire Department rescuing four residents from basements and removing 19 occupied cars from floodwaters.

The nearly 500-acre Green-Wood Cemetery is a uniquely large place that has a significant impact on overflows that end up in the East River — just one of the ponds accounts for nearly 11% of the overflow in the Owls Head sewershed.

“We were aware of the significant impact that Green-Wood has on the sewer shed here, and we knew that we wanted to figure out a way to manage that better,” said Joseph Charap, vice president of horticulture at Green-Wood. “Our goal is to use Greenwood as the sort of model site for how we can continue to build in more climate resilience throughout the landscape.”

‘Shifting the Time’

The projects at Green-Wood — five years in the making — have yet to be tested by a downpour, but together promise to handle as much as 60 million gallons of rainwater a year, according to Matt Rea, director of strategic partnerships at the Nature Conservancy, a global non-profit that assisted with the efforts.

“This was the first project on private property that the state and city ever co-funded,” Rea said. “It’s a huge site, and it’s unique in that it has a lot of siting ability to capture water.”

Water rushing down the slopes of the hilly cemetery has led to flooding and erosion, necessitating costly fixes. The deluge last September ruined two vehicles in the service yard, which is located in a relatively low-lying area. Charap said he hopes to avoid such losses now that the underground retention tanks should mean there’s less flooding.

During heavy rainstorms, water routinely overtops the banks of Sylvan Pond, flowing all the way to a bench several feet away. Now the pond is outfitted with technology that predicts when heavy rain will fall and releases water into the city sewer system before then so the pond area can fill back up during the rain event instead of stressing the sewers.

“You’re shifting the time you release water,” Rea said.

Much of that stored water can later be used to irrigate the lawns and plants on site at Green-Wood.

Not too far from the pond, cars drive directly over porous pavers, installed in a zig-zag pattern over four large areas on the roadway. At first, Green-Wood staff considered rain gardens, absorbent patches of plantings alongside roadbeds, but opted for the pavers instead.

“We moved away from the rain gardens because the cost to build them and the ability to match the aesthetic of a rain garden in a historic landscape just became too difficult to really navigate,” Charap said. The pavers “allowed us to capture more storm water and also not change the historic feel of the landscape.”

Already a national historic landmark in recognition of its landscape design, architecture and famous deceased residents, from artist Jean-Michel Basquiat to conductor Leonard Bernstein, Green-Wood Cemetery is now taking on yet another role that points to the future.

“Everyone has a role to play: private property, government property, nonprofit property, academic property. Everyone that has a footprint in New York City needs to do their part either to convey or collect water,” said Amy Chester, director of Rebuild by Design, which in 2022 issued a report mapping out how to make the concrete jungle more absorbent.

“In the case of trying to channel rain to safer places, it’s really a life or death situation.”

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