At the tip of lower Manhattan, New York City is building a a massive system of floodwalls and floodgates, in preparation for rising sea levels and more powerful storms. The City also plans to bury a waterfront park under 8 to 10 feet of landfill, raising the land to help hold back the water in future storms and try to avoid what happened in Hurricane Sandy in 2012, when nearly 5 feet of water submerged the area.
It’s a controversial project—a thousand large trees will be cut down in the park, while earlier plans had called for a nature-based approach that would have left part of the existing park in place to absorb water rather than act as a barricade. It’s also expensive, with a price tag of $1.45 billion. And it’s only one part of New York City’s 520-mile-long coastline. In a new project, the design, architecture, engineering, and planning firm HOK explores how the rest of the city could adapt to rising sea levels.
The challenge is huge: By 2100, as the population in New York City grows to 10 million, the sea level could be 6 feet higher. “When you look at that 6 feet of sea level rise and what’s going to be underwater in the future, we’re looking at 20,000 acres of the city and about 280,000 residents,” says Bill Kenworthey, planning leader for HOK’s New York practice, who previously worked on a resiliency plan with the Bloomberg administration, which was based on earlier, lower projections of sea level rise. Perhaps as many as a third of those at-risk residents, he says, will be living in public housing. Another 1.4 million residents will be at risk from periodic flooding. Hundreds of healthcare facilities, 18 power plants, 52 subway stations, and more than 19,000 acres of parks are also at risk from flooding or going permanently underwater.
In the project, as the designers mapped out where sea level rise will impact the city, they also looked at where there’s currently space to build on higher ground. Vacant lots, parking lots, and other underbuilt spaces sit on 7,300 acres within five minute walks of existing and planned subway and light-rail stations. Some of that land could be used to build new housing in dense, mixed-use neighborhoods so people and businesses could move out of the areas most at risk.
In Brooklyn, for example, the area next to the Gowanus Canal could revert to the wetland that it once was; park space near the water could be used in dry weather, and go underwater in a flood. Nearby, in the Park Slope neighborhood, some low-rise buildings could be replaced by denser development. The planners envision a redesigned street with wider sidewalks for more public space, bike lanes, and green space to absorb more water in heavy rains.
In the Queens neighborhood of Hunters Point—where a new park was built on a former landfill a few years ago to help absorb stormwater—the designers suggest that retail space along the waterfront could be designed to flood as the East River rises. “I think we’ll be looking at wet ground floors for active spaces when we’re this close to the water, potentially,” says Kenworthey.”So market spaces can be used during good days. But in bad days, they can be easily dealt with and swept out and hosed out.” Existing roads nearby may have to be raised to deal with the higher water. Along some streets with high-rise buildings, a second layer of public spaces—including parks and playgrounds—could sit above the street level.
The designers aren’t saying that these specific ideas have to happen. But because the changes that have to happen are major long-term projects—and flooding is already happening now—New Yorkers need to start considering how they want the city to change. “It’s not about any one of these visions being right, as much as what’s possible,” Kenworthey says. “How we can create a really energetic urban city, thriving in the future, in the face of all these issues with sea level rise, and knowing we’re not going to build a 500-mile wall, right? We have to start with nature and live with water in order to accommodate a lot of what the future is going to bring.”
The city is already investing in other flood-protection measures, retrofitting buildings and making critical infrastructure, like wastewater treatment plants, resilient in future storms. “Rising sea levels are a serious cause for concern, and some of New York City’s lowest lying neighborhoods are already seeing localized flooding impacts on sunny days,” Jainey Bavishi, director of the Mayor’s Office of Climate Resiliency, said in an email. “We’re addressing this threat with a resiliency plan of more than $20 billion. We will continue to partner with leading climate scientists to monitor emerging developments.” A “comprehensive water plan” from the department, informed by a panel of climate scientists, will be finalized by the end of the year, with a framework to help guide future development. But the city—and residents in every neighborhood that will be affected—will still need to decide exactly what adaptation will look like.