The Storm Warnings Were Dire. Why Couldn’t the City Be Protected?

The warnings and maps seemed clear.

On Tuesday evening, the National Weather Service issued a prediction that a wide swath of the Ohio Valley and the Eastern Seaboard would soon see heavy rainfall from what had once been Hurricane Ida. And one of the reddest portions of those maps — indicating severe rainfall and a high probability of flooding — hovered directly over New York City.

Those predictions proved true. But the record intensity of the rain, with more than three inches falling in one hour, caught officials by surprise. And on Thursday, as the death toll in the Northeast rose to 43 people, including 23 in New Jersey and 15 in New York, questions quickly arose as to whether city and state officials were caught flat-footed by the storm’s ferocity.

The destruction in the New York region seemed especially striking considering that Ida had already blown through the Gulf Coast, hitting New Orleans on Sunday with far stronger winds but with fewer deaths.

It also came in the wake of a series of ever-more-powerful tropical storms — including 2012’s Hurricane Sandy — which have been repeatedly cited as warning signs that the city’s aging infrastructure and subways are vulnerable to the violent weather caused by climate change. The subways, in particular, have come to act as a default sewer whenever heavy rains overwhelm the city’s actual sewer system.

The storm’s devastation underscored the city’s increasing fragility in the age of global warming, but also illustrated how the unpredictability of weather events can topple even the best laid of plans.

The city issued official warnings early Wednesday morning, when the city’s Office of Emergency Management cautioned that the remnants of Ida could cause flash flooding. The city said it also activated its flash flood emergency plan, which involved cleaning out clogged catch basins. It put its downed-tree task force on alert.

State transportation officials were dispatched to clear culverts and other drainage systems of debris, according to the governor’s office, with inspections and patrols to assess rising waters. An array of equipment — from chain saws to hand tools — was deployed, as well as pumps and generators.

By Wednesday evening, the warnings had grown more dire. New Yorkers were warned of tornadoes and urged to move to higher ground. Calls to the city’s 911 emergency system and 311 helpline began to surge around 8 p.m., according to city officials.

For all that, the intensity of the rains surprised forecasters.

Arthur DeGaetano, director of the Northeast Regional Climate Center at Cornell University, said the flash floods of Wednesday night resulted from not one storm but several small storms whose interactions with each other were hard to foresee. In the end, those storms ended up running over New York City, one after another.

“It was just like New York City was on the train tracks, and the storms were a train going down those tracks and they persisted for hours,” he said. “I would say that the forecast for this storm, or the remnants of this storm, of heavy rain over the city a day in advance were actually pretty darn good. I don’t think anybody at that point in time could have imagined six inches of rain in a six-hour period, essentially.”

Indeed, on Aug. 21, Central Park saw rainfall of 1.94 inches in an hour, a byproduct of Hurricane Henri, and the most rain-per-hour in record keeping history. On Wednesday night, 3.15 inches fell in one hour, eclipsing that record.

Although no one could foresee the fierceness of two weather events 10 days apart, city officials in May released a citywide analysis of flooding caused by rainfall.

The report sought to grapple with predictions that the city would experience an increase in “extreme rainfall events” over the course of this century, including a possible 25 percent increase in annual rainfall and a substantial increase in the number of days with more than an inch of rain.

Part of that plan included a commitment by the city to update its flash flood response procedures. Among other things, it said that by 2023, the city should “predraft messaging regarding potential dangers for residents living in basement dwellings to be used for outreach and notification in advance of forecasted extreme rain events.”

The city has also put money behind its effort to make the city more resilient to water, including a $2 billion commitment toward enhancing drainage in Southeast Queens. It was unclear how much of that has been spent.

But the storms that hit New York this week pre-empted long-term strategic planning by city officials, inflicting a more brutal real-world reality: On Thursday, officials said at least 11 New Yorkers had died in flooded basements, most of them in Queens.

For his part, Mayor Bill de Blasio suggested that the experts had led the city astray.

He said that originally, the city was told to expect three to six inches of rainfall over the course of the whole day, something he cast as “not a particularly problematic amount.” Instead, he said “with almost no warning,” the city got the single biggest hour of rainfall in its history.

“We’re getting from the very best experts projections that then are made a mockery of in a matter of minutes,” Mr. de Blasio said. “We need to start communicating to people that we should assume things are going to be much worse in literally every situation.”

There was strong pushback to the mayor’s remarks, especially from elected officials who represent communities outside Manhattan.

“I think anyone who is saying they were surprised or caught off guard is being disingenuous,” said Justin Brannan, a councilman who represents Bay Ridge in Brooklyn and is chairman of the Committee on Resiliency and Waterfronts. “The one thing we can agree on is that these storms are getting more frequent and getting worse.”

Mark Treyger, a councilman who represents Coney Island and Bensonhurst in Brooklyn, noted that a federal plan to study resiliency in the area was recently postponed, even as the city embarks on the $1.45 billion East Side Coastal Resiliency plan to protect Lower Manhattan, which is scheduled to be completed in 2023.

“I’m not questioning the needs of Manhattan in terms of resiliency. I’m questioning the sense of equity across the five boroughs,” Mr. Treyger said.

Mr. Brannan is the sponsor of legislation that would require the city to develop a plan to protect the city’s entire 520 miles of shoreline. The legislation had 38 sponsors but has not moved in part to concerns over cost from the de Blasio administration.

Mitch Schwartz, a spokesman for Mr. de Blasio, said the administration supported the “intent” of the legislation but said that studying even one neighborhood for a plan of that size would cost millions of dollars. The City Council may move to pass the legislation before the mayor’s term ends in January.

A separate $10 billion plan from Mr. de Blasio to artificially extend the southern tip of Manhattan by 500 feet to create a berm well above sea levels that would protect from storm surges seems to still be in the preliminary phases more than two years after it was proposed, with community engagement underway, Mr. Schwartz said.

But Klaus Jacob, a special research scientist at Columbia University’s Earth Institute, suggested that the future of New York City lies elsewhere.

“New York City’s future will lie in its higher elevations, not in its lower elevations,” said Mr. Jacob.

The resiliency of the city’s subways — which suffered switch malfunctions, floods and systemwide shutdowns and slowdowns during the storm — has also been a long-term concern.

On Thursday, the president of the transit workers union, Tony Utano, said that the Metropolitan Transportation Authority needs to “redouble efforts to fortify the subway system against flooding,” including stopping “water from cascading into stations.” Service disruptions continued into Thursday afternoon.

Janno Lieber, the acting chair of the authority, blamed a large part of the problem on the nature of the city’s street drainage system, noting that there were numerous ways for water to flood into the subterranean tracks.

“The subway system is not a submarine,” he said.

Gov. Kathy C. Hochul — facing her first natural disaster since taking office last week — had warned of a strong storm, issuing a news release on Wednesday morning cautioning that some downstate areas could see “six or more inches of rain” as well as “flash flooding and dangerous travel conditions in several locations.”

On Thursday, the governor declared a state of emergency for the city and suburbs, saying she had spoken to President Biden and congressional leaders about the need for more money for infrastructure improvements.

She also defended the state’s response to the storm, but suggested that the M.T.A. and other entities could face questions about their performance. “Did we have enough warning? Did we let people know? Should we shut down subways earlier?” Ms. Hochul said.

She said that preparation for flash flooding in the city and elsewhere was not adequate, noting loss of life and property in basement properties. “It’s not waves off the ocean or the Sound,” she said. “It’s flash floods coming from the sky.”

Still, when the rain falls at a historic pace, city officials say there is little they can do to prevent widespread flooding, given the age and condition of much of the city’s infrastructure. Vincent Sapienza, the city’s environmental protection commissioner, acknowledged on Thursday that the city was ill-prepared for these sorts of events.

“Anything over two inches an hour, we’re going to have trouble with,” he said.

Luis Ferré-Sadurní contributed reporting.