Millions of Americans think they’re safe from flood waters. They aren’t.

A new, nationwide flood modeling tool released Monday paints a picture of the U.S. as a country woefully underprepared for damaging floods, now and in the future.

The federal government’s best efforts to predict where flooding will strike have underestimated the risk to nearly 6 million homes and commercial properties primarily in the nation’s interior, leaving them unprepared for potential devastation, the analysis shows.

Meanwhile, the model prepares residents of coastal states and cities for risks to come as their communities head toward a future of more intense storms and rising seas.

Experts say the analysis is the latest evidence of a decades-long bungling of flood planning and policy at multiple levels of government across the country. And it presents difficult new questions about who will pay billions of dollars to save communities from going underwater: homeowners, towns and cities, or the U.S. taxpayer?

“Who is going to pay and how we are going to pay, is the ultimate question,” said A.R. Siders, a professor at the University of Delaware’s Disaster Research Center.

The analysis was conducted by the First Street Foundation, a nonprofit organization that paired dozens of scientists and engineers with researchers from academic institutions including the University of California-Berkeley, George Mason University and Rutgers University. The team combined several existing models of sea level rise, riverine flooding and simulations of extreme weather events into a single, nationwide flood assessment model that examined risk in all states except Alaska and Hawaii.

While insurance and investment companies, such as Blackrock, have long used their own private models to make decisions, First Street will allow users of its Flood Factor site to view flood risks to individual properties and created a Flood Lab that allows academic researchers to further access data for research.

The group's modeling is “exactly what we need to be doing,” said Kerry Emmanuel, a professor of atmospheric science at MIT who serves on First Street’s advisory board.

“Until recently we didn’t have people putting all these little pieces together,” he said. “We had really good people working on that little piece of the problem and good people working on another little corner.”

First Street’s newly combined model found that about 14.6 million homes and other structures across the country currently face a 1% annual risk of flooding, representing about one out of every 10 such real estate parcels nationwide. But First Street calculated that current maps developed by the Federal Emergency Management Agency list just 8.7 million properties in the floodplain, a 40% undercount compared with what First Street found.

And the situation is getting worse. In addition to a present-day analysis, First Street’s modeling incorporated 2050 projections from the International Panel on Climate Change, the United Nations’ primary scientific body on the issue. The conclusion: Another 1.6 million properties will be at 1% annual risk of flooding by 2050.

The 1% threshold is the gold standard used by the federal government to assess which homeowners are required to purchase flood insurance. But experts say it’s also misleading, as it actually equates a 1-in-4 chance of flooding over the course of a 30-year mortgage. Local and county planners also use the threshold to determine which areas are safe to develop.

Many flood experts said the discrepancy between the two models wasn’t surprising, given the limitations baked into FEMA’s calculations. The federal agency is stretched thin, struggling to keep its flood maps up to date, particularly for inland areas perceived to be less vulnerable than the coasts, experts said. The agency also looks only at historical data to assess where flooding could strike next, leaving out current and future models that assess where else risk might exist or even be growing.

Grover Fugate, former executive director of Rhode Island’s Coastal Resources Management Council, said he butted heads with FEMA over floodplains during his nearly 35 years with the council. FEMA revamped its flood maps along the state’s coast in recent years and actually lowered storm-surge estimates by up to five feet where Fugate knew the opposite was true. His team took a closer look.

“We found that there were a series of mistakes with the FEMA maps that were alarming,” Fugate said.

Fugate said the agency hadn’t accurately accounted for the way winds would drive waves inland during massive storms, and also used a 50-year-old model to predict the way a storm surge would begin moving over the land.

The discrepancies led Fugate’s team to develop its own flood maps with what they felt were better models. As a result, his team found that FEMA had underestimated wave height during extreme storms by as much as 16 feet.

“We now use those in the state for our purposes,” Fugate said.

Eric Tate, a professor at the University of Iowa who early in his career built flood modeling tools as a FEMA contractor, agreed the agency’s maps can be outdated, miss lower-priority areas and at times become subject to political influence through a revision process.

“As a result of all of these, there’s a lack of uniformity nationwide,” said Tate, who plans to use First Street’s data in his research. “You have a map here that’s based on this set of data, and this way of analysis. And then you have another map somewhere else, and it’s different.”

FEMA’s maps and First Street’s model depict different kinds of risk and serve different purposes, said FEMA Press Secretary Lizzie Litzow.

The federal agency is charged by Congress with mapping current flood risk and its flood data is used for floodplain management and for life and safety during a flood event. It works with local and state government officials to gather information to prepare and update maps and allows local officials to submit additional data to ask for map revisions.

The agency sees First Street’s Flood Factor as a tool to inform a property owner’s decision to buy flood insurance or take steps to reduce individual flood risk, Litzow said.

FEMA’s maps remain the backbone of effective floodplain management, said David Maurstad, the agency’s deputy associate administrator for Insurance and mitigation. Local adoption of minimum standards based on the maps helped avoid $100 billion in losses over the past 40 years, he said.

FEMA’s regulatory maps depict the 1% chance annual event, but flood risks exist outside that flood plain, Litzow said. By the agency’s own accounting, 20% of flood claims come from properties outside high-risk flood zones.

Although people try to compare flood maps to actual events, Litzow said, it’s “not an apples-to-apples comparison.”

Still, First Street’s analysis, which used a uniform modeling system across the lower 48 states, helps expose the potential scale of missed risk. Many of the largest discrepancies are driven by states and cities not typically considered at high risk for flooding. In California, nearly 600,000 properties are at 1% annual risk for flooding under First Street’s model, but not under FEMA’s. That’s the largest gap of any state, driven by big jumps in cities like Los Angeles and Fresno.

Similar gaps exist in New York, Pennsylvania, Texas and Tennessee, driven by underappreciated risks in cities such as Philadelphia and Chattanooga.

Chicago leads among all cities: First Street calculates that nearly 76,000 additional properties there should be in the floodplain.

Officials with the Metropolitan Water Reclamation District of Greater Chicago weren’t surprised to learn of the discrepancy. FEMA’s models have difficulty with urban flooding and that's Chicago's biggest problem, said Rich Fisher, the district’s principal civil engineer.

The region has experienced several significant flood events during the past 20 years, including a national disaster declaration in 2013. Between 2007 and 2014, more than 90% of the insurance claims were for properties outside of the federally designated floodplain, Fisher said.

The implications of First Street’s findings stretch far beyond huge urban centers.

Under its calculations, no state is more at risk than West Virginia, where mountainous terrain has historically forced communities to crowd near rivers and creeks in deep valleys. In that state, nearly one out of every four properties reach the 1% risk threshold under First Street’s model, a higher proportion than in Florida and Louisiana and a significant jump from 1 in 10 properties under FEMA.

In June 2016, the risk became reality in West Virginia, when heavy rains led to flash flooding that killed 23 people in several counties.

But four years later, First Street’s analysis appears to show risks are still being missed in the state’s river towns.

In the tiny community of Rand, nestled tight against the Kanawha River about six miles southeast of Charleston, just 2 percent of homes currently fall within FEMA’s 100-year floodplain. That figure jumps to 93% under First Street’s model, one of the largest such increases of any community in the entire country.

“When I think about our towns and terrain, Rand isn’t alone,” said Angie Rosser, executive director of the nonprofit West Virginia Rivers. “Most of our areas where people live are right up against rivers and streams.”

Even more dramatic increases occur along the Gulf Coast in communities in Florida and Texas.

In Pine Manor, a neighborhood several miles south of Fort Myers, Florida, only 0.3% of properties now reside in FEMA’s 100-year floodplain. That jumps to 99.6% under First Street’s analysis. The nearby neighborhoods of Warm Mineral Springs and Whiskey Creek also see properties within the floodplain jump to nearly 100%.

Jim Beever, a scientist who retired earlier this year from a regional planning council that helped cities in Southwest Florida model floods, said FEMA maps have traditionally not paid much attention to storm surge in the area and are “very broad-brush.”

'CARFAX for homes'

In addition to releasing a report with its findings, First Street has created a “Flood Factor” tool that the company promotes as a way for homeowners and buyers to evaluate any given property’s risk for flooding. The tool also allows users to review whether the property flooded in the past, and receive wider statistics for their ZIP code, county, and state.

Some say the application has perhaps the greatest implications for any use of First Street’s model. While the tool likely won't immediately transform the real estate market, experts predict it will grow as Americans become more familiar with the tool and others like it.

“This sounds like a CARFAX for homes,” said Larry Bartlett, the property appraiser for Volusia County, Florida, home of Daytona Beach.

While Bartlett figures some will doubt the data, just like they doubt sea level rise, others, especially mortgage lenders, would find the updated information invaluable.

“If I was a lender, I’d want to know if the property I was lending money on stood a good chance of being underwater in 30 years,” Bartlett said. “If it gets to the point where people are relying on the data, it will definitely affect property values, but I don’t think we’re there yet.”

Others said that the current inability for prospective homebuyers to evaluate the true flood risk and history is a crucial problem nationwide.

“We have long been doing a poor job at communicating flood risk,” said Carolyn Kousky, executive director of the University of Pennsylvania’s Wharton Risk Center and a First Street advisory board member.

Determining whether a home sits in a floodplain or not is only the first step, Kousky said. Also important is how severe flooding may be, which can inform decisions such as whether or not a home should be elevated or what amount of insurance to purchase. Decisions are further complicated by the fact that with few exceptions, most prospective buyers cannot ascertain whether or not a home was previously flooded.

“Markets aren’t efficient if there’s not full information,” Kousky said, adding she hopes the new tool will help arm buyers with more information.

But several experts urged caution, noting all models have limitations.

William Sweet, an oceanographer with the National Oceanic and Atmospheric Administration, said the new model may be a “big step forward” in understanding risk. But no model is perfect, he said, and there are still gaps in the understanding of how likely certain weather events are to occur.

“We’ve only been well-positioned to monitor these things in the last 50 to 75 years,” Sweet said. “How do we make assumptions and assessments about today’s risk when we can’t really model and monitor all the components that go into calculating that risk?”

Chad Berginnis, executive director of the Association for State Floodplain Managers, further warned that nationwide models by their very nature miss nuances at the local level. Urban flooding is particularly difficult to pin down and often requires detailed and expensive analysis of stormwater infrastructure.

“There is not going to be a national model that is the panacea to answer all flood risk questions,” Berginnis said.

But for at least one potential buyer, the model rings true.

Kristina Johnson, 23, has flooding on her mind as she checks out homes in the Savannah, Georgia area.

Her Acura TSX flooded in September 2017, when she was forced to leave it behind while evacuating from Hurricane Irma. She left it parked at her apartment complex on the city's south side.

It was flooded to the steering wheel, Johnson said, and she had to get a new car.

"And that actually was not a flood zone," she said.

However, on First Street's list, the complex has seven apartments scored with a high flood risk. Johnson said she's keeping that experience in mind as she considers a new home.

'You’re not going to tell me I can’t live here.'

While determining a community’s flood risk is challenging, experts say equally as daunting is figuring out what to do next.

Decisions about building in flood zones are almost entirely made by local and county governments. Each face their own unique challenges, and many find it difficult to give up the short-term benefits of waterfront development because of the chance of a flood decades down the road.

Fugate, the former regional planner in Rhode Island, said an official in the town of South Kingston used to remind him that the first row of houses from the beach accounted for 20% of the municipal tax base. In coastal areas, waterfront property owners are also typically wealthy and hold political clout that enables them to push back on development limitations or financial penalties.

“The incentives are stacked against” local leadership to respond proactively, said Siders, from the University of Delaware.

But Tate said historically disadvantaged communities, not wealthy ones, face the greatest challenges from flooding. His recent research has found that the populations exposed to the highest levels of flood risk are disproportionately African American, Native American and residents of mobile homes.

The problem becomes exacerbated by the fact that many such communities don’t have the resources to pay for their own flood maps to better understand where risks exist.

“Many of these counties and communities that have lower capacity are also places where the economics aren’t as strong, or there’s a higher percentage of racial minorities,” Tate said.

Rand, in West Virginia, offers a real-world example. Census data shows the poverty rate there is 27%, more than double the national average. Black residents make up one third of the population, much higher than the 13% national figure.

In recent weeks, after heavy rains brought flooding to portions of Rand, local TV station WOWK reported that neighbors felt the state had failed to maintain drainage culverts, exacerbating the flooding. A local state delegate, Amanda Estop-Burton, created a Facebook post calling attention to the issue that was shared hundreds of times by local residents. Many commenters tied the issue to what they felt was a chronic underinvestment in the community.

In an interview, Kent Carper, a commissioner of Kanawha County where Rand resides, expressed skepticism when told about First Street’s model showing the town in the crosshairs for pervasive flooding. He’s distrustful of such predictions because of his experience with FEMA flood maps he believed to be inaccurate.

“I’ve never had a lot of confidence in these computer modeling programs,” Carper said. “90 percent of this stuff is generally driven by someone making money.”

But Carper is no stranger to the dangers of flooding. Six county residents died in the 2016 floods, after which Carper described the flooding as “Our Katrina” to the Wall Street Journal.

Carper said Rand has its own “difficult struggles,” and that placing such communities into floodplains can make affording insurance “impossible for people.” Carper highlighted other priorities, such as rebuilding critical infrastructure still damaged by the 2016 floods.

“We still have high school children that haven’t had a school building now for four years,” Carper said.

Rosser, with West Virginia Rivers, in many ways agreed. Her own home, situated an hour northwest of Rand, was flooded in 2016, despite not being within FEMA’s 1% floodplain. She said the community has yet to recover, with dilapidated houses standing abandoned after residents moved on.

She also feels trapped financially.

“My house is livable but I haven’t re-furnished it, because anytime it rains I still have in the back of my mind, ‘Is it going to happen again?’” Rosser said. “But nobody will buy my house.”

Even still, future flooding risk is low on the worry list for residents. Drinking water problems, aging sewer infrastructure, the ongoing opioid crisis, and a lack of access to broadband internet and jobs all loom large.

“It’s hard to look beyond the immediate basic needs to think about flood protection and resiliency,” Rosser said.

And unlike in coastal areas, retreat isn’t an option. There’s no building homes halfway up a mountain, Rosser says. Not that some would even want to.

“I talked to people here locally in 2016. They wanted no part of FEMA, because they were so scared they were going to be forced to move,” Rosser said. “You have land that has been in families for generations, and a very kind of independent, self-reliant culture here. It’s ‘You’re not going to tell me I can’t live here.’”

Who pays?

The problem with putting flood risk on the backburner is that someone has to pay for it, experts say. The economic harm driven by devalued real estate and insurance premiums is real, but so too are the costs of picking up the pieces after a flood hits.

“There’s always been this kind of tension between wanting to protect home values, but also wanting to be clear about risks and manage those risks effectively,” Kousky said. “Those price adjustments reflect a real underlying risk.”

And currently, U.S. taxpayers subsidize that risk, Kousky said. The federal government’s National Flood Insurance Program is the primary provider of flood insurance policies, which is required by law for any property with a federally-backed mortgage within the 100-year floodplain.

Kousky said the program has been underwater ever since Hurricane Katrina wiped out its coffers in 2005, followed by additional hits from Hurricanes Ike, Sandy, and Harvey. In 2017, Congress voted and President Donald Trump signed off on $16 billion in debt forgiveness for the program. The money theoretically should have been paid back to the federal government for use elsewhere.

FEMA has set aggressive targets for increasing insurance coverage and closing the insurance gap, Litzow said, and is making some progress working with state, local, and industry partners to help at-risk communities and promote flood insurance.

The agency “is constantly working to improve the production of the Flood Insurance Rate Maps within the context of changing conditions,” Maurstad said. “We’re exploring ways to leverage new technologies and provide flood information more efficiently, accurately, and consistently across the nation.”

Experts say there are no easy fixes, as each solution creates its own problem. Raising premiums can disproportionately hurt disadvantaged communities and drive people away from insurance. Requiring more disclosure about risks and past flooding can penalize those who are honest and reward those who aren’t.

“A fundamental piece of this is trying to decide from a public values perspective, how much catastrophic risk we want individual homeowners to bear, and how much we think should be socialized,” Kousky said.

Flooded future

Ticking away in the background is the reality that the situation is only getting worse.

Baking in future climate change projections, First Street’s model anticipates rapid growth in the number of at-risk properties in coastal cities, particularly along the Gulf Coast.

This year, First Street’s model shows about 48,000 properties in New Orleans are within the 100-year flood zone, or a little less than one-third of the city. By 2050, nearly 100,000 more will be added to the list, or 98% of the city. Elsewhere in the state, the communities of Chalmette and Meraux will see 99.9% of homes reach the 1% risk threshold.

In Florida, First Street projects Jacksonville will see 19,000 properties added to the floodplain. Around the same number will be added in Cape Coral, sandwiched between the Gulf of Mexico and the Caloosahatchee River. On the opposing banks of the Caloosahatchee, Pine Manor will have fallen entirely into the floodplain.

FEMA does have a Hazardous Mitigation Grant Program that buys out at-risk homes and relocates residents to higher ground. Siders said the program has purchased about 45,000 homes since first established in 1989. Although the number may seem large, it only amounts to about 30 homes per state per year.

Meanwhile, new development within floodplains continues in many communities across the country.

“We can’t figure how we’re going to pay for the homes that are already at risk, and now we’re adding more, and we’re adding more by the thousands,” Siders said. “That means we’re putting thousands of more families at risk, with no plan for how we’re going to pay to help them get out in the future.”

Contributing: USA TODAY data reporter Theresa Diffindal and Savannah Morning News reporter Mary Landers

This article originally appeared on USA TODAY: Real estate: Millions more homes risk a flood, might need insurance