But most of it is due to better modeling methods developed in the past 30 years, said Orton of the Stevens Institute of Technology, as well as better computers and better scientific understanding of ocean physics.
The maps offer a far more optimistic view than the picture that actually emerged when the city was hit by Sandy. The storm caused an estimated $50 billion in economic danages, with New York bearing about a third of the losses.
The roughly 9-foot storm surge and 70 mile-per-hour winds submerged large areas of Queens, Brooklyn, Staten Island and New Jersey that aren't included in FEMA's new flood zones. The destruction more closely resembled maps published five years ago in a report called "Nation Under Siege," which set out to show the permanent flooding New York City could experience if sea levels continue to increase from global warming.
FEMA officials said they are aware that storms are becoming more frequent and more intense from climate change, and that the flood zones could change as a result. The agency rushed to release the redrawn maps last week because despite possible flaws, they're more precise than the 1986 maps and are needed for the Sandy recovery process.
The maps are preliminary and can't be used to enforce new building laws until approved by the New York City Council and government officials in surrounding areas.
Property owners in high-risk zones could be required to elevate their buildings an average of three to six feet on poles or take other action to protect their structures from flooding. Building owners who don't comply with the new flood guidelines could face sharp increases in insurance premiums. FEMA officials estimate that annual insurance rates for single-family homes that don't meet the guidelines could jump from $1,400 to an estimated $9,500 a year, according to media reports.
Orton said FEMA should make it clear to property owners that the new maps don't anticipate future problems caused by climate change.
"If you're planning for 50 years in the future, which is at least how long houses can last, it wouldn't hurt to anticipate a few more feet of sea level rise and build appropriately," he said.
Lauren Passalacqua, a spokesperson for New York City Mayor Michael Bloomberg, told InsideClimate News the maps are a good basis for rebuilding, but that the city is "also working to develop maps that project future climate change scenarios, including flooding risks, to further inform our citywide resiliency plan."
Dan Watson, a spokesperson for FEMA, said the agency plans to update its flood maps across the country roughly every five years from here on out. "In 2003, FEMA began receiving a regular appropriation to both modernize and update the science behind flood insurance rate maps," he said. "The continued funding allows us to maintain the mapping of flood risk as a top priority."
FEMA researchers will at least have to consider incorporating future climate impacts, per the new law.
New York State Governor Andrew Cuomo isn't waiting for FEMA to determine whether, and by how much, climate factors will expand the flood zones.
He announced late last month that he wants to immediately spend as much as $400 million buying up homes ruined by Hurricane Sandy, including those located outside the new flood zones. The program would demolish the structures and leave the land empty to serve as a buffer for the next big storm. The plan still needs to be approved by federal officials and could face tremendous opposition from affected communities.
"At one point, you have to say maybe Mother Nature doesn't want you here. Maybe she's trying to tell you something," Cuomo told the Daily News.