15 million U.S. homes are at risk of flooding — 70% higher than FEMA estimates

Think the risk of your home filling up with floodwater, magnified these days by climate change, is only an issue near the coasts and rivers? New research detailing nearly every corner of the U.S. shows otherwise. 

Researchers from Brooklyn-based nonprofit First Street teamed with more than 80 experts in real estate, insurance and academia to compile an unprecedented flood database extensively augmenting existing federal information. For the first time, the general public can look up nearly every individual address nationwide to assess the risk of a property flooding as it exists today and — crucially for homeowners — how that threat is likely to change over the next 30 years. 

The database already make one thing clear: Many more Americans are in danger than previously known. Some 14.6 million properties are at immediate risk of flooding nationally — 6 million more than the federal government previously calculated. By the year 2050, that figure is projected to top 16 million, according to First Street.

Never before mapped

In some parts of the country, including in non-coastal states, the flood assessment is being compiled for the first time. That's because the Federal Emergency Management Agency, which maps flood risk, lacks the budget and other resources to map every square inch of the country, and instead concentrates on the most vulnerable areas.

Where FEMA's maps are available — in about 87% of the country — First Street's data also offers far more granular information that what was available. That enables more rigorous risk estimates by insurers, property owners and house-hunters, First Street researchers said.

That has implications across housing and commercial properties, from homebuyers and sellers to mortgage lenders, realtors and even municipalities that rely on property taxes to fund their budgets — many of which are trying to gauge flood risks exacerbated by climate change.

A FEMA spokesperson said the agency was "encouraged" by the First Street project, and noted that it complements federal data. "Specifically, the accuracy of the flood data necessary for making decisions regarding floodplain management or life and safety during a flooding event is different than the level of accuracy necessary to inform someone's decision to acquire flood insurance or take an action to reduce their individual flood risk," the spokesperson said.

Has your house been flooded?

First Street is making it possible for anyone to look up the flood risk for individual properties through the website FloodFactor.com. The online service will give a 1-to-10  score for each property to indicate how vulnerable it is to flooding. The real estate website realtor.com also plans to offer First Street's data as part of the information available to homebuyers at an unspecified date. 

That means the cost of flood insurance and the home's predicted value may emerge earlier in the home-buying process, rather than surprising buyers or sellers at the last minute, Danielle Hale, realtor.com's chief economist, told CBS MoneyWatch.

"A lot of homebuyers may be surprised at the types of properties that would be in flood zones," Hale said. "So they can have a conversation early and think about what their risk level is" and make decisions "earlier rather than later in the transaction, when no one really wants to be surprised."

Before the First Street project, there was no public database to find out how likely a specific property is to flood — or even if it has been flooded in the past. Nearly half of U.S. states allow home sellers to hide information about previous flooding from buyers. And while federal maps are used to calculate government disaster aid, more detailed information is often compiled by private financial companies, like insurers or hedge funds, and kept private.

Rising risk

First Street found millions more properties around the U.S. that are at risk of flooding risk than what FEMA maps indicate. In the most extreme cases – in Utah and Washington, D.C. — the analysis revealed five times as many at-risk properties than shown on FEMA's existing maps.

Just three states overall — Arizona, New Jersey and Louisiana — have a lower count of properties currently with substantial flooding risk in First Street's model compared with government data, according to the report. But using the nonprofit's projections, more properties in those states show higher risk through 2050 as waters are expected to rise.

"If you're FEMA and you have limited money, you're going to create and deploy resources that will have the biggest impact for the biggest financial risk in the country," Matthew Eby, First Street's executive director, told CBS MoneyWatch. "And even though your mission is to do the whole country, you just can't" because of budget and other constraints.

One of those constraints: Fully updating FEMA's flood maps could cost as much as $11 billion, according to a January study from the Association of State Floodplain Managers, which also noted that only one-third of the nation's rivers and streams, and half of its shoreline, have flood information mapped out through FEMA. 

Meanwhile, a June 25 U.S. Government Accountability Office report found that FEMA's flood insurance program is more than $20 billion in debt to the Treasury and "continues to put taxpayers at financial risk." 

FEMA has long sought more government funding to more precisely model the risks of flooding on life and property. The agency also recently said it wants states and municipalities to do a better job of quantifying risk so FEMA can be better prepared to help.

The First Street model

First Street draws on info from 55 previous hurricanes, tropical storms, nor'easters and "major inland flooding events" to create its model for future flooding using hard-to-find data. The model also uses current tidal, storm surge, rainfall and river-line flooding data to calculate risk for individual homes and small businesses.

Not surprisingly, coastal states are particularly vulnerable — more than 1 in 5 properties in Florida and Louisiana is a flood risk today. But the threat is also apparent much farther inland. In landlocked West Virginia, for example, nearly half of the properties in some counties are in danger of flooding. In Montana and Idaho, nearly 1 in 6 properties is at risk.

First Street initially looked at 12 inland states and found that 3.6 million homes are at risk for flooding under its own definitions. That is triple the 1.2 million homes at risk as calculated by FEMA.

Add to that increasingly destructive weather, like hurricanes, and properties could lose value with each extreme event, said Linda Shi, an assistant professor at Cornell University's department of city and regional planning who focuses on urban and environmental governance. Shi is among dozens of academic teams using First Street data for research.

A "goldmine" of data for researchers

The detailed data has big implications for states and municipalities themselves, which rely on tax revenue for their budgets. If properties lose value or residents move away due to flooding, that could mean less revenue at a time when budgets are hurting because of coronavirus.

For researchers who study public infrastructure financing, the database is a "goldmine," not only because of its detail but also because the data are more updated than what the federal government is able to provide, said Douglas Noonan, a professor at Indiana University's O'Neill School of Public and Environmental Affairs, who is among the academics working with First Street's data. 

That's become increasingly important in terms of the economic health of a region, he said. First Street's data could be "hugely valuable because we then know where flood damage has occurred. Looking at a state disaster declaration doesn't tell us much about what's on the ground," Noonan told CBS MoneyWatch.

Local banks already avoid flood-prone areas

The private sector is already taking note. Banks are already increasingly dumping mortgages in coastal areas, a 2019 study foundy. And local banks — those most familiar with individual properties — are selling off mortgages for homes susceptible to flood risk the fastest, according to a recent report by Tulane University's Jesse Keenan and Harvard's Jacob T. Bradt. That leads the way to what they call "bluelining."

When lenders stop writing mortgages for a given geographic area, infrastructure — roads, schools, bridges, services — also degrades, said Keenan, an expert on the impact of climate change on real estate. 

"That only accelerates the current disinvestment that we're starting to see along the coast because of climate change," he added. 

"Double-edged sword"

Some researchers question the release of such detailed data about individual homes — potentially threatening the biggest investment many Americans have made — at a time when the nation lacks a coherent plan to deal with rising seas and increased flooding.

On one level, Keenan said, people should be aware that their home may lose much — or even all — of its value over the life of a 30-year mortgage. But he also called it a "double-edged sword."

"That's a public service in a way," Keenan said. "But the downside is that there's a lot of intervening things that can happen in terms of localized adaptations," including interventions that save or preserve a specific area and that projections don't account for.

Rachel Cleetus, policy director for the climate and energy program at the Union of Concerned Scientists, co-authored a 2018 report that found millions of households could be at risk of chronic flooding by the end of the century — and that most homeowners were unaware of their risks. 

She, too, has mixed feelings about making individual data public because it shifts responsibility to homeowners for problems that they didn't create, and that the government has been slow to solve. 

When it comes to climate change, Cleetus said in a January interview with CBS MoneyWatch: "[R]isk disclosure is a necessary prerequisite, but that's not enough. It's also not enough to tell people's flood risk in specific places. What are their options? They've made an investment that, to most of us, is the single biggest investment that we'll ever make. And to see that decline would be devastating. We have to have policies in place, whether it's home buyouts, managed retreats" or other policies.

"Remember federally backed mortgages? We were on the hook," she added. An uncontrolled collapse of the mortgage market, as buyers flee flood-prone properties, could be much worse than the last housing bust, she said.