Climate change isn’t just affecting the living. During Hurricane Sandy, the dead were flooded in their tombs in low-lying graveyards across the city.
On the rolling verdant hills of Brooklyn’s Green-Wood Cemetery, the storm brought down about 300 trees and destroyed well over 100 tombstones. The roads and paths on the property were inundated in up to 4 feet of water, making it hard to get in or out.
This month, the nearly 500-acre graveyard announced a plan to protect its roughly 600,000 final resting places against future floods — while also keeping its tranquil gardens open to the public. This resiliency project will invest more than $2 million to store water in dedicated places well under the grounds, which would alleviate the burden on the city's sewers — the main source of the flooding problem.
“Water pools anywhere it needs to – even graves for that matter,” said Frank Morelli, facilities manager at Green-Wood Cemetery. “But we do whatever we have to do because tomorrow someone needs to be buried and nothing's going to stop that.”
To mitigate flooding on the landmark funerary grounds’ paved surfaces, rain gardens along roads and paths will capture additional stormwater that would otherwise make roads inaccessible or send a deluge into the ponds. The project aims to alleviate up to 2 inches of stormwater from the sewer system and store it for irrigation. It is the first design under the Resilient NYC Partners program, a $53 million municipal initiative launched in June 2021 to help private property owners green their land and manage onsite stormwater.
“If you want to solve this challenge, which is basically managing the rain where it falls, you have to come up with partnerships like this one,” said Craig Holland, senior director of investments for the Nature Conservancy’s Healthy Cities Program. The Nature Conservancy is an adviser on the project. “Cemeteries are one of the largest land uses in suburban and urban properties in the United States,” he added.
The program’s strategy will focus on reducing sewer overflow, and that means moving beyond funding climate resiliency for just public property. In partnering with private property owners, the city government hopes to spread flood protection all over the five boroughs.
In New York City, about half the land is privately owned. Cemeteries, which account for 2% of New York City’s land area, provide a unique opportunity to leverage greenspace for water management. This project could serve as a prototype for similar properties, such as golf courses.
“In order to manage the volume of runoff that we have in large storm events, or even just small storm events, we need to make sure that we're doing the right projects in the right places,” said Valerie Strassberg, global director of urban water infrastructure at the Nature Conservancy. “That doesn't always align with where public land is most available. And that's the case in New York City.”
Though the 184-year-old burial ground has onsite drainage and catch basins, its stormwater management is dated according to the New York City Department of Environmental Protection, which is chipping in $600,000 in municipal funds into the project. The state Environmental Facilities Corporation will finance the rest as part of its Green Innovation grants program with state funding.
“Green-Wood is actually holding back a huge volume of rainfall, which allows for the city to kind of have a little bit more of a buffer and insurance against flooding,” Strassberg said.
As it is now, the Sunset Park necropolis is suffused with trees and grass. Some precipitation infiltrates these unpaved surfaces, but most stormwater runs off downhill into one of the four bodies of water onsite due to the hilly topography. Sylvan Waters Pond, the largest one at nearly 3 acres and a maximum depth of 17 feet, is at a low point. The adjacent Valley Pond and onsite catch basins drain into Sylvan.
“It [stormwater] creates its own path and it'll just take out a road or gutters,” Morelli said. “It'll just start washing it away because the force of all that water coming down in such a manner, it makes its own little river and it just deteriorates the whole thing right away.”
During Hurricane Ida, the land around Sylvan was flooded up to 20 feet beyond its shores. The pond drains directly into the city sewer.
The new improvements would equip Sylvan Pond with a sensor linked to a weather station run by an algorithm. When the forecast calls for heavy rains or storms, the sensor will automatically release 2 inches of water into the sewer in advance, while it can still handle it. Doing so will create additional storage for the anticipated precipitation in the pond. When the rains are heavy, the weir shuts down, preventing any additional water from flowing from Green-Wood Cemetery into the sewer system.
“There's a public benefit to the city for water quality improvements,” said Melissa Enoch, managing director of green infrastructure, capital planning, and partnerships at the DEP. “But there's also a public benefit to the surrounding neighborhood because Green-Wood is going to do what they can to keep the stormwater from running off of their property into the streets.”
Exploratory work will begin this fall with borings that will help classify the soil and calculate the infiltration rate. The results will guide rain garden placement in areas where the ground absorbs water best. It will also include subterranean water storage that will double as a reservoir for providing moisture to the plant above via their roots.
The work will also include additional water storage underneath the service and maintenance yard where vehicles and equipment are kept. This large paved area is not only a substantial source of runoff, it’s also prone to flooding. The underground structure will manage stormwater for this spot and prevent it from entering the sewer.
“These acts will lessen our impact on the outflow of the Owl's Head sewer shed that we affect, which 27,500 of our neighbors use,” Joseph Charap, director of horticulture at Green-Wood Cemetery. “If they [Green-Wood] can serve as a model for other cemeteries to recognize that there is funding available for work such as this, that not only enhances the climate resilience of their site, but also serves the community good.”
The one-year construction project will break ground in spring 2023.