Many Americans are buying homes in flood zones—and don't realize it
The Flood Insurance Rate Maps used by FEMA are based on antiquated data and obsolete models. As a result, the U.S. government downplays flood risks for homeowners across the country—but especially in mountainous regions like Appalachia.
When Hurricane Helene barreled up the Gulf of Mexico last month, people on the Florida and Louisiana coasts braced themselves for the extensive flooding heading their way. But residents of North Carolina and Tennessee were stunned when water rushed into their homes and businesses. To a lesser extent, some residents of Florida were similarly taken aback by flash flooding from Milton two weeks later. The inundations were unexpected because most of the properties were outside of the federal government’s officially designated flood zones.
For years, experts have criticized the maps created by the United States’ Federal Emergency Management Agency (FEMA), officially known as the Flood Insurance Rate Maps (FIRM), as woefully inadequate. The FIRM maps have extensive problems, from the data it includes and excludes to the limited assumptions around how the maps would be used.
As a result, across the U.S., “millions of homes should be labeled as high flood risks but aren’t,” says Susan Crawford, a senior fellow for sustainability and climate at the Carnegie Endowment for International Peace.
FEMA’s maps underplay risks everywhere, but especially in mountainous regions like rural North Carolina and Tennessee where Helene unleashed the most catastrophic flooding. When the research organization First Street developed its own national flood-risk assessments, “the place where we found the biggest discrepancies between our models and the FEMA flood models was Appalachia,” says Jeremy Porter, head of the group’s climate implications research.
Climate change has raised the stakes for insufficiently flagging flood-prone locations. Rising temperatures could increase heavy precipitation by 50 percent by the end of the century, according to the United Nations’ 2023 climate report. Warmer waters in the Gulf of Mexico made Helene’s rainfall 10 percent heavier—leading to more than 200 deaths across the southeast and causing billions of dollars in damage—and future storms may be worse.
(Why is flooding one of the biggest hurricane hazards?)
“We need a concerted, nationwide effort to have the best risk-assessment available. But right now, the federal government basically says, ‘Pick your own risk, decide what you think is coming to your neighborhood,’” Crawford says. (FEMA did not respond to a request by National Geographic for an interview.)
FEMA’s maps weren’t created to warn
FIRM’s shortfalls date to their creation in the 1960s, prompted by new laws passed to better protect and insure properties from flood. While federal maps for earthquake risks served to educate communities, these maps had a different objective—to encourage home ownership.
Water gauges provided the best historical data for oceans and major rivers, so mapmakers primarily focused on neighborhoods near these large bodies of water. FEMA labels those deemed at highest flooding potential as special flood hazard areas, and federal law mandates flood insurance for mortgage-backed properties there.
In Asheville and its surrounding towns in western North Carolina, only a small number of homes carry this designation, because they are close to the Swannanoa River.
Damage outside of areas categorized as high risk by FEMA is so common that more than three-quarters of the properties that flooded during August’s Hurricane Debby were beyond FEMA's designated flood zone, an analysis by First Street found. As with Helene, this storm also struck the Florida coast but went on to drop tremendous rainfall in states far inland.
Many of the maps are also decades old. FEMA has tried to update some areas, but when they do, communities often push back.
The process by which FEMA and the community must agree played out publicly after 2012’s Hurricane Sandy extensively flooded South Brooklyn, New York, an area not previously considered high risk. City officials feared FEMAs new maps would force more building owners to purchase insurance and would lower property values and therefore tax revenue, Porter says. After a lot of back and forth, “the final map looks nothing like what FEMA originally proposed,” with a much smaller area tagged a hazard, he says.
Property values do in fact decline when accurate risks are calculated. Some homes in South Florida’s Miami-Dade County lost an average of four percent of their value in 2009 following their added designation in a flood zone, another of Porter’s studies found.
(Experts weigh in on how to prepare for extreme weather.)
Accurate maps require a whole new approach
Even if FEMA could fix these issues, the problem goes much deeper, to the models upon which the maps are based, experts say. First, flooding from rainfall causes a lot of the property damage but is generally not taken into account unless it causes rivers to overtop their banks.
By fixating on large bodies of water, the models also ignore small waterways like streams, creeks, and tributaries. “With climate change, we’re seeing heavier rain events, and the small waterways are the areas most likely to flood from them,” Porter says.
What’s more, the maps largely ignore the residential and commercial development that has extensively occurred over the years. New buildings, parking lots, driveways, and sidewalks pave over soil and greenery, dramatically reducing the ground’s ability to absorb excess rainwater. “Water flows to rivers, not just away from them,” says Sam Brody, an environmental scientist and director of the Institute for a Disaster Resilient Texas (IDRT) at Texas A&M University. Water can flow underground, but in complexly built environments it will carve its path through neighborhoods.
Asheville’s population and resulting development exploded in recent decades, so flooding was inevitable, Brody says. “The rainfall of Helene was epic, but what the city did with its 25-year development train was load up the risk. No one talks about that,” he says.
In much of the country, land developers have especially disregarded how projects impact low-lying land in the vicinity. Due to historical prejudices and redlining, that land is often home to minority communities. That’s why Crawford considers flooding to be a social justice issue as well. After studying Charleston for her recent book, Charleston: Race, Water and the Storm to Come, she found these communities “have some of the worst flooding and inadequate drainage systems in the city.”
Developing better flood maps demands a different approach to modeling. Brody’s organization is already doing this in Texas. In 2017, Hurricane Harvey dropped over 30 inches of rain across Houston in less than a week, causing major flood damage and killing more than 60 people. After studying the storm’s fallout, the institute abandoned conventional, physics-based modeling and turned to statistical models using big data and artificial intelligence. For every parcel of land mapped so far (in 41 of the state’s 254 counties), the institute’s computers account for land development, impervious surfaces, home elevations, and many other factors in addition to historical flooding.
High-risk areas flagged by Texas’ system are termed damage plains rather than flood plains, and they extend for many miles beyond FEMA’s hazard zones. In fact, the new model determined that three times more structures in the Texas Gulf Coast are actually at high risk of getting inundated.
Is your home at risk?
In addition to checking your property on the FEMA maps, you can find the flood risk for your home using First Street’s Risk Factor website, and, in Texas, the IDRT website Buyers Aware. Understanding the flood risk of a home is especially vital for purchasers. (Zillow began integrating First Street’s data into listings last month.) Only some states require sellers to disclose whether they’re in a FEMA flood zone and even fewer, including Florida starting this year, mandate revealing that the home has previously flooded.
(Here’s how to stay safe in a flood.)
People in the FIRM’s special flood hazard areas should understand the almost-certain target on their home’s back. The designation indicates a one percent annual risk of a destructive “100-year flood.” That may not sound like much, but over the life of a 30-year mortgage, this translates to one-in-four odds.
FEMA recommends that everyone, not just those in these hazard areas, purchase flood insurance. (Most homeowners’ and renters’ policies don’t cover flooding unless there is a separate rider.) Some 92 percent of properties at true risk of flooding lacked flood insurance as of May 2023, the Congressional Budget Office estimates.
Insurance can be costly, especially after the National Flood Insurance Program hiked prices in 2021. But without insurance, homeowners are stuck with a whopping bill. As little as one inch of water entering your home produces $25,000 in damage, FEMA notes. First Street found that some $10 billion of the wreckage caused by Hurricane Debby occurred outside FEMA’s hazard zones and was likely mostly uninsured.
Without clarity on true flood risks, people will continue to move into flood-prone communities instead of to areas more likely to stay dry. Transitioning to lower-risk locations is especially important as climate change intensifies the expected flooding.
“Where should we plan to live as our world changes? And how can we plan for an incremental, orderly transition to that future? This is what we should be asking,” Crawford says. “As long as the vast majority of the public doesn’t understand the risk it faces, millions of Americans may be cast into misery when we could have been planning for this all along.”
