Pastor Aaron Trigg was at home when the water arrived in Rainelle. It had been raining hard all day, filling the creeks and rivers that run through southern West Virginia. In the past, such intense downpours would last only a few hours, but this storm brought wave after wave of torrential rain.

"You could hear the water up in the mountains just crashing trees," Trigg remembers.

Rainelle is a small town in a steep valley. When the creek near downtown jumped its banks on the evening of June 23, 2016, the water immediately flooded into every home on Trigg's block.

Trigg's house was one-story tall, so there was nowhere to escape. He took shelter on the second floor of his neighbor's house and waited as the water kept rising. As it got dark, he could hear people screaming for help. He wondered if he would survive the night. "I did a lot of praying that night," he says. "Not so much for myself, but for the people I could hear."

Trigg was rescued by boat the next morning. The home he and his wife lived in was destroyed, as were almost all of the other homes on their block. In all, at least 23 people died in the 2016 West Virginia floods, and an estimated 1,500 homes and businesses were ruined.

Rainelle is one of hundreds of small towns where climate-driven flooding potentially poses an existential threat. Sea level rise and heavier rainstorms driven by global warming are sending more water into residential neighborhoods from the Gulf Coast to New England to Appalachia to the Pacific Northwest. And new data make it clear that many households and communities cannot afford the mounting costs.

More than 4 million houses and small apartment buildings across the contiguous U.S. have substantial risk of expensive flood damage, according to data released by the First Street Foundation, a nonprofit research organization that studies flood risk and housing. The cost of flood damage to homes nationwide will increase by more than 50% in the next 30 years, the First Street Foundation estimates.

"These properties are going to face a significant economic loss over this 30-year period, and it's something they're just not built to defend against," says Matthew Eby, executive director of the First Street Foundation.

Residences at risk for expensive flood damage are concentrated on the coasts and in Appalachia. But there are hotspots across the country, including parts of the West that are increasingly threatened by wildfires as well.

Poorer people stand to lose the most to flooding as the climate changes, and the federal government is ill-prepared to address the problem through the current federal flood insurance program.

A looming insurance disaster

The federal government provides the vast majority of residential flood insurance in the U.S. Most policies are underpriced relative to the actual cost of flood damage.

The new data show that flood insurance rates would need to more than quadruple to keep up with the costs of climate-driven flooding. The Federal Emergency Management Agency is already preparing to raise insurance premiums in many places later this year in an effort to save the National Flood Insurance Program, which has accrued more than $36 billion in debt.

FEMA warns that the First Street Foundation's analysis is only an estimate and that FEMA didn't provide the research group with details about the new flood insurance pricing plan, known as Risk Rating 2.0.

"Any entity claiming that they can provide insight or comparison to the Risk Rating 2.0 initiative, including premium amounts, is misinformed and setting public expectations that are not based in fact," writes David Maurstad, the senior executive of the National Flood Insurance Program, in an email to NPR. "While entities are free to suggest or estimate their opinion of what flood insurance premiums should be, they are offering exactly that — an opinion — and they do not have insight into the Risk Rating 2.0 initiative."

For homeowners who are currently underpaying for flood insurance, FEMA says it plans to raise rates by up to 18% each year until the price is accurate, according to a January report by the Congressional Research Service. The agency will begin rolling out the new pricing in October.

As the cost of insurance goes up, many people who need flood insurance will likely be unable to afford it, leaving them to face lasting damage. Research has found that disasters can erode family stability and exacerbate mental and physical ailments when people don't have the money they need to repair their homes.

"If you don't have the finances you need to recover, then families have to make really difficult trade-offs, like maybe forgo spending on medical expenses because otherwise you don't have a safe home," says Carolyn Kousky, the executive director of the Wharton Risk Management and Decision Processes Center at the University of Pennsylvania.

When large numbers of people don't have insurance or savings after a disaster, the effects can ripple through the community. Towns like Rainelle are a bellwether for that future. Here, flood insurance is already unaffordable for many residents, and climate-driven flood damage has already exceeded local resources. About a third of Rainelle residents live below the poverty line, and the cost of repairing the 2016 flood damage was insurmountable for many families.

Trigg's displaced congregants would call him, hopeless, in the months after the flood. "A lot of people in Rainelle were poor, and they didn't have any insurance. They didn't have any way to have any backup plan," he says.

With no money for repairs, many people took what they could salvage and left Rainelle for good. "It affected the spirit of the town," Trigg says. Nearly five years later, a lot of homes are gone or only partially repaired. Trigg says all but one of the families on his block left. The city government saw a 10% decrease in water utility customers, a proxy for population loss.

"It's shocking," says John Wyatt, a member of the Rainelle City Council.

Still, Wyatt is an optimist of sorts when it comes to the town's future. He's running for mayor, and he imagines Rainelle hosting an Appalachian music festival and attracting hiking tourists. "This town has so much to offer," he says. But if there's another big flood, he adds, "I can't see our town surviving."

Paying for the damage

Flood damage is also skyrocketing in wealthier parts of the country. But the financial calculus there is different, because homeowners can afford flood insurance — at least up to a point. And municipal governments are able to invest in expensive flood mitigation projects.

In Alexandria, Va., flash floods after rainstorms and high tide flooding have damaged dozens of homes and affected hundreds of residents in recent years, according to the city government. Climate change is largely to blame for the rapid increase in damage in the waterfront suburb of Washington, D.C.

The First Street Foundation data suggest that in one particularly hard-hit area of a neighborhood called Del Ray, the cost of flood damage will increase by 76% in the next three decades.

The city has responded to that threat by creating a flood mitigation "strike team," which has proposed spending nearly $500 million for stormwater management over the next 10 years.

"We've got to make some investments in the size of the infrastructure, the pipes," says Yon Lambert, the director of Alexandria's Department of Transportation and Environmental Services.

The city is also planning to dramatically increase its budget for stormwater maintenance: When debris and silt clog drainage pipes and culverts, it can lead to flooding on the streets above. "When we look 10 to 15 years out, we see a city that is more resilient to these climate change-induced rainfall events," Lambert says. He is confident that the city's plan will lead to significantly less flooding.

Still, many homeowners in Alexandria, where the median household income is just over $100,000, are concerned about the rising cost of flood damage and insurance. And they're emotionally exhausted by what feels like endless flooding.

Diana and her husband moved into their house in Del Ray in 2018. Three months later, they had 5 feet of water in their basement and a small lake in their backyard. Since then, the house has flooded three more times — once in 2019 and twice last year.

"It's terrifying," says Diana, who didn't want her last name used because she thinks that talking publicly about flood damage could hurt the value of her home. "After so many repeated floods it's traumatizing."

The floods have been a big financial burden. Diana and her husband spent tens of thousands of dollars raising the backyard by a foot, putting in a new drain, installing new sump pumps in the basement and sealing the walls of their house. When you include belongings they've lost to flood damage, Diana estimates that the flooding has cost their family more than $50,000 over the past three years.

That's on top of the flood insurance policy they bought after the first flood, which runs more than $1,000 per year. If they didn't have insurance, their out-of-pocket costs would have been even higher.

They've considered moving, but so far they've decided to stay and hope the city can fix some drainage problems quickly. "I absolutely don't see how a single-income family would be able to sustain even one flood," Diana says.

Indeed, other homeowners in the area tell NPR that they know people who have moved away as the financial and emotional costs of flood damage have increased. The local government is aware that flood damage could drive people away, and Lambert says that's one reason the city is being aggressive about fixing the problem. The city is even planning to help some residents pay to flood-proof their houses, since bigger drainage projects will take years to complete.

That's a safety net that is unavailable to residents of poorer towns. In Rainelle, Councilman Wyatt says the city doesn't have the money to repave roads downtown that were damaged by the 2016 flood, let alone help homeowners rebuild.

Getting a better deal

Overhauling the National Flood Insurance Program could offer some relief to towns like Rainelle. Reforms could help low-income residents pay for flood insurance or require that some amount of flood coverage be included in all home insurance policies.

Congress has considered such changes, as well as new requirements that flood risk be disclosed to homeowners and renters before they move in. But so far the efforts have stalled. Elected officials of both parties fear that their constituents could pay a lot more for flood insurance than they expected when they bought their homes.

Yet the current flood insurance system is already unfair to many homeowners. Although most federal flood insurance is underpriced, some policies are more underpriced than others, which ends up helping more affluent people.

The new data show, for the first time, where the federal government is subsidizing flood risk the most. For example, a family might pay less than $1,000 each year for their flood insurance even though the annual cost of flood damage to their house is expected to be $3,000. The bigger the gap, the better the deal.

Nationwide, people are getting the best deals on flood insurance in communities where the median income is higher. Those places include wealthy neighborhoods in Sarasota, Fla., Charleston, S.C., and exclusive suburbs of Chicago, Houston, Los Angeles and New York.

Kousky, of the University of Pennsylvania, says one reason for that disparity might be that flood insurance premiums don't currently take into account how expensive the house is. "The end result is that low valued homes are paying too much, and high valued homes are paying too little," she says.

NPR also found that homeowners who are getting a better deal on flood insurance live in whiter neighborhoods.

In the mostly white, affluent suburb of New Castle, Del., flood insurance premiums cover less than a third of the expected cost of flood damage. And two hours south, in the even wealthier, majority-white beach towns of Rehoboth and Dewey, flood insurance premiums cover less than 4% of the expected cost of flood damage.

But for residents of the historically Black neighborhood of Southbridge in Wilmington, Del., it's a different story. They are subsidizing flood insurance for the rest of the country, including whiter areas in suburbs such as New Castle and the wealthy beach towns in southern Delaware.

In Southbridge, where flooding is already a big problem, the new data show that flood insurance premiums are appropriately priced to cover flood damage. If anything, residents are slightly overpaying.

Richard King, 59, is a cook and a lifelong resident of Southbridge. He recently took over as leader of its civic association, which has historically advocated for flood mitigation measures in the neighborhood.

King remembers his single mother struggling to find affordable flood insurance when he was growing up, and he says the cost of flood insurance is still a problem for many residents. There are other factors as well: Many houses in Southbridge are not required to have flood insurance because they are not in the official floodplain or because they were passed down through generations, as King's was, and no longer have mortgages.

Still, "[if it were] easy to access and more affordable, I think a majority of people here would jump on it," King says. "Because that's a big bill that a lot of people can't afford when your basement gets flooded and the damage is done. Because you got your heater and everything else down there. So all that is just about wiped out."

King is not surprised by NPR's findings that residents of Southbridge are getting a worse deal on flood insurance compared with residents of wealthier, whiter parts of the state. "We're the prey," he says. "We're the prey, so they take advantage of us."

Fixing one problem, creating another

The details of who wins and who loses when it comes to flood insurance could be useful for Congress and FEMA as they address climate risks. President Biden has said that helping Americans adapt to a hotter Earth in an equitable way is one of his priorities.

When FEMA begins to raise flood insurance rates later this year, it plans to begin factoring home value into its calculations so that people who own more expensive homes pay monthly premiums that reflect their actual risk of flood damage. Those changes could help address the current race and income disparities in the cost of flood insurance.

FEMA's changes could also help reverse a decades-long trend of overdevelopment in floodplains. Artificially cheap federal flood insurance has incentivized developers and residents to build in places that are more and more likely to be underwater.

But new flood insurance prices would also create a massive affordability crisis, the Congressional Research Service report notes.

FEMA doesn't have the power to fix the affordability problem it is creating. Matt Eby of the First Street Foundation says it's up to Congress to pass legislation to help people afford flood insurance. "This is only going to be a bigger problem in the future," Eby says.