With its 520 miles of coastline and thousands of acres of waterfront development, New York has more residents living in high-risk flood zones than any other city in the country. Hurricane Sandy, the devastating October 2012 storm, did $19 billion in damage to the city, and the pace of development along the water has only increased.
Now, after a year in which hurricanes ravaged Houston and the Caribbean, the Federal Emergency Management Agency is substantially redrawing New York’s flood maps for the first time in three decades. It is a painstaking process that will affect tens, if not hundreds, of thousands of people, determining how and where buildings can be constructed and the cost of flood insurance on everything from modest bungalows to luxury skyscrapers.
New York will be the first major metropolis to be remapped taking into account the realities of climate change, like rising sea levels and increasingly powerful storms.
The new models, for coastal areas stretching from Cape May to the Hudson Valley, will be used to shape the city’s future zoning, development and building standards to help it become more sustainable. As a result, FEMA and city officials say, New York could be an example for other places around the country.
But the maps will also be shaped by the history of New York, where 80 percent of properties were built before the current flood maps and requirements were in place, as opposed to 20 percent nationally, noted J. Andrew Martin, acting chief of FEMA’s risk analysis branch in New York. If those older buildings end up in high-risk zones, their owners could be required to buy flood insurance or make expensive modifications, adding costs that are beyond the reach of many working-class homeowners.
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The collision of science with political and economic realities means that the battle over how many more people will fall in the flood zones will be fought house by house, block by block, with millions of dollars at stake.
“It’s a game of inches,” said Elizabeth Malone, program manager of resiliency and insurance at Neighborhood Housing Services Brooklyn, a community group that counsels residents in flood-prone areas.
In New York, where more than 50,000 people are homeless, and where the mayor has pledged to create or preserve 200,000 units of affordable housing by the end of 2022, the FEMA maps could add further financial strain.
The city has already pushed back against FEMA. The agency proposed preliminary maps in 2013 — soon after Hurricane Sandy — that would have doubled both the area of flood zones and the number of people inside them. The city, in an unusual move, successfully challenged the scientific assumptions underlying the new maps.
In the coming weeks, formal discussions on the maps between New York City and the agency will likely begin.
There is no time to waste, said Mr. Martin, who has been on assignment in Puerto Rico in the wake of Hurricane Maria. “Sandy may not happen again like it did,” he said, “but there will be something very similar, and it’s not that far off.”
But the process will not be fast, and homeowners should be prepared to be in “limbo” for years, said Daniel A. Zarrilli, the city’s chief resilience officer and senior director for climate policy and programs. That may not be ideal, he said, but it is “better than it could have been had the city not worked to protect affordability and incorporate climate risks onto the maps. We don’t want to jack up insurance rates and cause a foreclosure crisis, and we want a smoother glide path to a better flood insurance program, and more accurate maps.”
An Affordability Challenge
The first time FEMA mapped the city was in 1983. Since then, only minor changes have been made. The agency was working on an update, as requested by the city, when Hurricane Sandy hit.
A month later, Mayor Michael R. Bloomberg underscored the urgency of that task in a speech at a downtown hotel by displaying a map with the current flood zone, followed by a second with the areas actually flooded by the hurricane.
The audience gasped at how far the flooding had exceeded the mapped zone.
In the highest-risk zones on a flood map, waves can go higher than three feet. In the next zone, an area has a 1 percent chance of flooding in any year, in what is called a 100-year flood. In a moderate-risk zone, an area has a 0.2 percent chance of flooding in any year, in what is called a 500-year flood.
Put another way, houses in a high-risk zone have a one-in-four chance of being flooded over the course of a 30-year mortgage, compared with a 10 percent risk of having a fire. Federal law requires anyone with a mortgage in the highest-risk areas to get flood insurance.
But being on the map is not a particularly reliable predictor that a home might get flooded: About 80 percent of people who suffered flood damage from Hurricane Sandy did not have flood insurance.
Indeed, the maps have been long been viewed as inexact. One recent federal report estimated there was a 40 percent “uncertainty of flood predictions.”
In 2015, in its highly technical 180-page challenge to FEMA’s proposed new maps, the city argued that the federal agency had overstated the base flood elevation — the height of flooding that might be expected in a 100-year flood — by two feet in some areas. FEMA also inflated the flood zone area by a third, the city claimed, “unnecessarily putting approximately 26,000 buildings and 170,000 residents” in higher-risk locations and “causing an affordability challenge.”
In March, at the city’s request, the RAND Corporation detailed the maps’ potential impact in Brooklyn, Queens and Staten Island. The report found that the proposed maps could “reduce property values, increase loan defaults, lower tax revenue, and create hardships for current residents.”