More than 84,000 buildings worth over $129 billion lie in flood zones in New York City, according to an analysis released by the Office of New York City Comptroller Scott Stringer on the two-year anniversary of Hurricane Sandy.
"It's easy to think that Sandy was a 'once-in-a-lifetime event,'" Stringer told VICE News, "but climate science tells us that rises in sea level and more frequent severe weather will put lives, property, and communities at increased risk."
The report examined new flood maps from the Federal Emergency Management Agency (FEMA), which extend the areas of the city that are at-risk from a flood that occurs once in a hundred years, meaning areas that have a one percent chance of flooding each year. That area now includes an additional 60,000 structures that were not identified as at-risk in FEMA's 2010 maps.
The value of properties located within areas now identified as at-risk of severe flooding has increased 120 percent since 2010, according to the report.
The biggest spike occurred in Brooklyn, where the value of at-risk properties jumped nearly 200 percent, from $12 billion to $36 billion. Manhattan saw an increase of 120 percent, while the Bronx, the city's northernmost borough, saw the smallest increase of 36 percent.
"When we talk about events like Sandy, I think sea level is really the big elephant in the room," Adam Sobel told VICE News. Sobel is an atmospheric scientist at Columbia University and author of Storm Surge, a book about Hurricane Sandy and climate change.
Storm surge occurs largely due to storm winds pushing ocean waters to shore. As global warming causes sea levels to rise — New York has already seen a foot increase since 1900 — less intense storms are needed to create a level of storm surge that threatens coastal property — and lives.
'Yes, it's a problem, and everybody knows it's a problem. Including FEMA.'
When Sandy hit, waters around New York City were five feet above a typical low tide. The storm pushed water levels up another nine feet, meaning a total of 14 feet of water surged above the city's usual low-tide.
"People that are born now could see Sandy levels of flooding every other year because of rising sea levels," Kim Knowlton, a scientist at the Natural Resources Defense Council (NRDC), told VICE News. "A storm even less powerful than Sandy could cause that amount of flooding in the city. We really need to take this into account."
In April, NRDC released a report stating that nearly 65 percent of the area flooded during Sandy was not listed on FEMA's flood maps. And though FEMA's maps detail only areas at risk from a 100-year storm, the report also found that FEMA is using outdated data that doesn't fully account for future effects of climate change on flooding, including leaving out sea-level rise that has occurred in the last 10 years.
The New York City Panel on Climate Change has predicted sea-level rise of between 11 and 31 inches by 2050.
The new FEMA maps are expected to take effect in 2016, and have in some cases dire consequences for homeowners, who now find themselves in flood zones and in need of flood insurance. Stringer's report identified 28,000 homes that could see their insurance premiums rise astronomically, from $429 a year to between $5,000 and $10,000 annually.
The Comptroller's analysis also criticized FEMA's mapping process for failing to take into account tax-payer funded resiliency efforts, like sea walls along Battery Park City or water permeable street surfaces, which over time should reduce flood risk.
"FEMA must regularly revisit and revise flood maps to chart the effects of an encroaching tide and take resiliency measures into account to mitigate increases in insurance premiums," Stringer told VICE News.
While the exact rates of future sea level rise are difficult to pin down, Sobel says, FEMA already incorporates some level of uncertainty into its risk assessments, and leaving sea level rise out of the mix is "overly optimistic."
"I think FEMA knows this, but they haven't decided how to deal with it," Sobel told VICE News. "Yes, it's a problem, and everybody knows it's a problem. Including FEMA."
Follow Laura Dattaro on Twitter: @ldattaro