Flash floods foreshadow a threatening reality in New York City

A severe storm dumped more than 7 inches of rain in less than 24 hours over parts of New York City on Friday, turning streets into fast-moving rivers and grinding subway travel to a halt as water cascaded into underground transit stations.

The storm, which hit just two years after flooding from the remnants of Hurricane Ida battered the five boroughs and killed at least 13 people in the city, laid bare how vulnerable the Big Apple’s aging infrastructure is to extreme weather events that are intensified by climate change. And more than a decade after Hurricane Sandy forced officials to rethink the meaning of climate resilience in New York City, it appears there’s still much to be done.

Heavy rainfall of up to 2.5 inches per hour were reported in some of the hardest-hit places. A number of roads were closed, cars were submerged and several city buses were trapped as a result of flash flooding. Subways, regional rail lines and air travel was suspended or severely delayed, and at least one school in Brooklyn was evacuated during the storm.

“The reality staring city leaders in the face, including in places like New York, is that the climate is getting more extreme, more unpredictable and requiring more investment,” said Joseph Kane, a fellow who focuses on infrastructure at the Brookings Institute, a nonprofit think tank. “Usually, it’s too little too late.” 

Steve Bowen, chief science officer for Gallagher Re, a global reinsurance broker, said extreme weather events like this are exposing how quickly risks are shifting in cities like New York as climate change intensifies rainfall and existing infrastructure gives out. 

A warmer atmosphere can hold — and deliver — more moisture, which can make storms more intense, Bowen said.

“The bottom line is that we have infrastructure in New York, infrastructure all across the U.S. and frankly in many, many parts of the world that is just simply not capable of withstanding the climate that we’re seeing today and certainly not the climate that is yet to come in the future,” Bowen said. 

Around 23 million people across New York, New Jersey and Connecticut were under flood watches on Friday. New York Gov. Kathy Hochul declared a state of emergency for New York City, Long Island and the Hudson Valley, calling the storm a “life-threatening rainfall event.”

New York City Mayor Eric Adams, who also issued a separate state of emergency, faced backlash for being slow to address the public and for not doing enough early on to warn residents about the seriousness of the situation.

Zachary Iscol, New York City’s emergency management commissioner, said that Friday was the city’s wettest day since Hurricane Ida. 

Hurricane Sandy, in October 2012, was supposed to have been a wake-up call to New York officials about climate and weather risks.

Sandy made landfall as a post-tropical cyclone near Atlantic City, and caused a catastrophic storm surge along the coast of New York and New Jersey. The storm cut power to 2 million New Yorkers and killed 43 city residents, according to the city comptroller’s office. Nearly 70,000 housing units were damaged or destroyed. The storm caused about $19 billion in damage to New York City. 

Not enough progress has been made in hardening New York to its climate risks since, according to the city comptroller’s office.  

“Nearly a decade after Superstorm Sandy and six months after Hurricane Ida, we have not done enough to prepare for future storms,” Louise Yeung, the comptroller’s chief climate officer, told the city council in April 2022. “Meanwhile, our decades-old infrastructure continues to age.”

A report from the comptroller’s office found that the city had spent only 73% of the $15 billion in federal grant funding given to the city after Hurricane Sandy as of June 2022. Most of the city’s own capital contributions to resilience projects had gone unused. 

Progress has been “plodding,” the report said. 

This flash-flooding incident and Hurricane Ida have added new concern, Yeung said in an interview. Many of the investments the city made after Hurricane Sandy — like constructing floodwalls, berms and levees — are geared to managing coastal flooding and sea level rise, not extreme precipitation. 

“Heavy rainstorms like the one we are seeing today are becoming our new normal as climate change intensifies,” Yeung said, adding that it’s a problem that requires different investments like expanding green infrastructure, upgrading the storm sewer system and investing in better real-time emergency communication that is prepared for localized flash flooding. 

“We are not fixing things at the pace our climate is changing and that’s going to continue to be a challenge every time we get one of these rain storms or hurricanes,” Yeung said in an interview. 

In Hurricane Ida, 11 people died after flash flooding overwhelmed and trapped them in their basement apartments, most of which aren’t legal residences or known to the city. The comptroller’s office found tens of thousands of basements were at risk of flooding and suggested the city register basement dwellings, require safety inspections and take steps to protect occupants, like installing valves that prevent sewer water from rising into cellars.

Mona Hemmati, a postdoctoral research scientist at Columbia Climate School in New York City, said the storm serves as a reminder of the vulnerabilities faced by coastal communities and how those vulnerabilities are compounded by climate change.

In densely populated cities like New York, flooding risks are heightened because of the built environment and lack of green spaces.

“There are huge amounts of impermeable surfaces in highly urbanized areas, which means water cannot seep underground, which creates a lot of runoff and urban flooding,” she said.

Hemmati added that the city’s stormwater management systems are outdated and were not designed to handle the level of runoff that is now a reality.

But Hemmati said the city deserved some credit for prioritizing climate resilience in rebuilding efforts after Superstorm Sandy, which included upgrading floodgates, fortifying shorelines and developing citywide models to study runoff flows in different climate scenarios. Other infrastructure projects, such as hardening storm barriers and the city’s subway system, will take more time — and money.

“I don’t expect every problem can be solved in just a couple of years, but it is getting better,” she said. “It is the right track, but it’s not enough, for sure.”

Hemmati said that in addition to state and local efforts, members of the public can also contribute to building climate resilience in their communities.

“Climate issues aren’t just happening at the government level,” she said. “With all these hazards — rainfall, flooding, wildfires, extreme heat — people should educate themselves about the risks.”

Bowen, from Gallagher Re, said most New Yorkers do not carry flood insurance on their properties, which puts their communities at risk. 

“I’m assuming that when we start to see some of the damage totals coming out of this, that a significant portion is just going to end up being uninsured,” Bowen said. “It’s just the latest data point that something’s gonna have to change.”

And the potential government shutdown, if prolonged, could present challenges as New Yorkers try to get back on their feet.

The National Flood Insurance Program’s authorization will lapse on Oct. 1 unless Congress takes action before then. The lapse will limit the program’s ability to borrow from the U.S. Treasury to pay out claims after a flood. The program will pay out claims from its reserves until it runs out of money, or Congress acts, according to the Congressional Research Service. 

The majority of employees at the Federal Emergency Management Agency are likely to be exempt from the shutdown, but other basic federal government functions could be slowed.