New York City’s Battle Against Extreme Rainfall Events
New York City is facing an increasing threat from extreme rainfall events, with a 2024 study in Nature revealing that the city’s stormwater system is being pushed to its limits. Since 1970, the system has been designed to handle up to 1.75 inches of rain per hour, but this limit has been exceeded in three of the last five years, according to data from Central Park’s rain gauge. This is a stark contrast to the past, when the hourly precipitation recorded by the gauge didn’t exceed this limit until 1995.
The city’s stormwater system is struggling to cope with the increasing frequency and intensity of rainfall events, and a major problem is the lack of absorption and storage of rainfall before it reaches the system. To address this issue, a range of solutions are being implemented, including the creation of rain gardens, permeable pavement, and the restoration of natural features such as streams and wetlands. Eric Sanderson, a landscape ecologist and vice president for Urban Conservation Strategy at the New York Botanical Garden, has spent years reconstructing the city’s past ecological landscape, producing data that will inform its future.
Understanding the City’s Historical Environment
Sanderson’s work has focused on imagining a more resilient urban future, one that is based on the city’s past topography. “I was trying to imagine a configuration of the landscape that could work with the understanding of climate change at the time,” he said. “Part of that is restoring streams, wetlands and agricultural lands, connecting the urbanized parts of the city, and depaving a lot of what we have.” By embracing absorption and restoring natural features, the city can reduce the burden on its stormwater system and create a more sustainable future.
Initiatives such as the Cloudburst program are already underway, with the city designing parks and public spaces to flood intentionally, enhancing their ability to act as natural catch basins. The first completed site, a basketball court in South Jamaica, Queens, can contain up to two feet of floodwater, which drains into an underground storage tank. Additionally, rain gardens in Gowanus, Brooklyn, are absorbing and redirecting water away from the sewage system, reducing the risk of flooding and combined sewer overflows.
Green Infrastructure and Stormwater Solutions
Policymakers are offering incentives to private property owners to install green infrastructure, making it easier for real estate developers to incorporate stormwater solutions into their designs. Waterfront properties above a certain size are now required to provide stormwater solutions, and the city is planning to upgrade its sewer and storage capacity. In Gowanus, Brooklyn, an eight-million-gallon underground tank has been installed, redirecting water that would otherwise flood the space. A new public park will be built on top of the tank, providing a green oasis in the heart of the city.
Other initiatives, such as daylighting, are also being explored. This involves unearthing and restoring onetime waterways, allowing floodwater to be redirected and reducing sewer overflow. A project at Tibbetts Brook in the Bronx will test this concept, removing concrete and artificial materials to reroute water aboveground and into a dedicated underground pipe. The successful Bluebelt project in Staten Island, which strings together streams, ponds, and wetlands, has already reduced flooding in parts of the borough and serves as a model for future initiatives.
However, expanding these initiatives to feasible locations will be a significant challenge. The city has identified 86 “priority areas” for flood mitigation, and the Department of Environmental Protection is working to find solutions for each specific location. As Rohit Aggarwala, the commissioner of the New York City Department of Environmental Protection, noted, “We’re asking, ‘What is the solution for this specific place?'” While there will be hurdles to overcome, including disruption to residents and the high cost of upgrades, the city must build for the future, not the past. As Aggarwala said, “We have to build for 2075, not 1975.”
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