After Hurricane Sandy flooded Lower Manhattan and caused massive damage to the city’s financial center, climate scientists agreed it was only a matter of time before a new superstorm would bring the same kind of damage — or worse.
That realization, in part, led Mayor Bill de Blasio to embrace an unconventional solution: Make Manhattan bigger.
To safeguard the area from the effects of climate change, including storm surges and rising sea levels, the city is proposing artificially extending the southern tip of Manhattan.
The idea would be to use landfill in front of the financial district and South Street Seaport to extend the coastline of the island by as much as 500 feet into the East River, creating a rising berm that would, at its highest point, be well above future sea levels.
The plan is similar to a 2013 proposal by Mr. de Blasio's predecessor, Michael R. Bloomberg, who called for creating a development, much like Battery Park City, along the East River, which would have been at least partly financed by developers interested in building residential or office towers on the new land.
But Mr. de Blasio’s plan and an accompanying study were short on details, and the mayor said the city did not have the estimated $10 billion it would take to pay for it. It would also have to go through environmental reviews and would be subject to input from the community, all obstacles that could alter or block the plan.
The mayor said the project should be financed by the federal government, which he said was unlikely as long as President Trump was in office, given Mr. Trump’s skeptical view of climate change.
Mr. de Blasio initially revealed the proposal in an online essay posted by New York Magazine on Wednesday night, headlined “My New Plan to Climate-Proof Lower Manhattan.” He wrapped the plan in the cloak of the Green New Deal, the proposal for a massive federal program to finance alternative energy technology and other initiatives aimed at building an ecologically sustainable economy, championed by, among others, Representative Alexandria Ocasio-Cortez.
Mr. de Blasio, a Democrat, has been toying with the idea of running for president, and since the start of the year he has made bold announcements aimed at gaining national attention. Earlier this year, he announced what he said was a universal health care system for city residents, but on closer scrutiny it amounted to a relatively small increase in the budget for the city hospital system.
The climate proposal, although couched in planet-saving terms, was largely a variation of earlier plans.
Mr. de Blasio said on Thursday that he did not know what would go on the new land created under his plan. He said that it might be open space and parks or that it could also contain buildings.
“Our focus is not private-sector development as it was” in the previous administration, Mr. de Blasio said at a news conference on West Street. “Our focus is on resiliency.”
He called his plan “audacious,” adding, “We had to come to grips with the sheer magnitude of what had to be done.”
Margaret Chin, a councilwoman who represents Lower Manhattan, said she was “sounding the alarm” about the potential for development on any new land that is created.
“You want to extend the shore line to protect the inland and not allow private developers to seize the opportunity to build tall buildings and take all the views,” said Ms. Chin. The area should remain as open space and the federal government should pay for resiliency measures, she added.
Mr. de Blasio’s plan also included some less ambitious elements for which the city has the financing. The city will spend $165 million to elevate the wharf and esplanade in Battery Park and to create a protective berm at the back of the park. And the city committed spending $200 million to build what officials called “flip-up barriers” along a nearly mile-long stretch of shoreline north of the Brooklyn Bridge, which could be activated to block a storm surge.
Construction of both those projects would begin in 2021.
“They’re certainly right to identify the climate and flooding risks to New York City and to Lower Manhattan, but I question the extent they’re considering the impact on the rest of the city,” said Nilda Mesa, a former director of the Mayor’s Office of Sustainability under Mr. de Blasio, who is now an adjunct professor at Columbia University. “Water goes where it will and you cannot contain it. If you’re going to keep it from coming ashore in one place it still has to move and what does that mean for Brooklyn, Queens and New Jersey and the Bronx?”
In pointing out the need for the plan, Mr. de Blasio emphasized the importance of Lower Manhattan for the city and the country, citing the area’s $60 billion worth of property, and characterizing it as “one of the core centers of the American economy” that contains one out of every 10 jobs in New York City.
“The security of Lower Manhattan should be a national priority,” the mayor said.
But Francisco Moya, a city councilman from Queens, called the city’s resiliency planning too “Manhattan-centric.”
“It can’t be a tale of two cities. The outer boroughs should not suffer because of rich development happening in more affluent areas,” Mr. Moya said in an interview. “The people of Queens pay taxes and we should not be ignored when it comes to the issue of climate change.”