FARMINGTON, W.Va. — In Senator Joe Manchin’s hometown, a flood-prone hamlet of about 200 homes that hugs a curve on a shallow creek, the rain is getting worse.

Those storms swell the river, called Buffalo Creek, inundating homes along its banks. They burst the streams that spill down the hills on either side of this former coal-mining town, pushing water into basements. They saturate the ground, seeping into Farmington’s aging pipes and overwhelming its sewage treatment system.

Climate change is warming the air, allowing it to hold more moisture, which causes more frequent and intense rainfall. And no state in the contiguous United States is more exposed to flood damage than West Virginia, according to data released last week.

From the porch of his riverfront house, Jim Hall, who is married to Mr. Manchin’s cousin, recounted how rescue workers got him and his wife out of their house with a rope during a flood in 2017. He described helping his neighbors, Mr. Manchin’s sister and brother-in-law, clear out their basement when a storm would come. He calls local officials when he smells raw sewage in the river.

“These last few years here in West Virginia, we’ve had unbelievable amounts of rain,” Mr. Hall said. “We’ve seriously considered not staying.”

Mr. Manchin, a Democrat whose vote is crucial to passing his party’s climate legislation, is opposed to its most important provision that would compel utilities to stop burning oil, coal and gas and instead use solar, wind and nuclear energy, which do not emit the carbon dioxide that is heating the planet. Last week, the senator made his opposition clear to the Biden administration, which is now scrambling to come up with alternatives he would accept.

Mr. Manchin has rejected any plan to move the country away from fossil fuels because he said it would harm West Virginia, a top producer of coal and gas. Mr. Manchin’s own finances are tied to coal: he founded a family coal brokerage that paid him half a million dollars in dividends last year.

But when it comes to climate, there’s also an economic toll from inaction.

The new data shows that Mr. Manchin’s constituents stand to suffer disproportionately as climate change intensifies. Unlike those in other flood-exposed states, most residents in mountainous West Virginia have little room to relocate from the waterways that increasingly threaten their safety.

Adding to the problem, West Virginia officials have struggled to better protect residents, despite a surge of federal money, experts say. They point to a reluctance among state officials to even talk about climate change, and to housing that is not built for the challenge, leaving West Virginia less able than other parts of the country to adapt.

The measure that Mr. Manchin opposes, a clean electricity program, may be the last chance for Congress to reduce planet-warming emissions before the effects of climate change become catastrophic.

A clean electricity program would reward utilities that switch from burning oil, gas and coal to using wind, solar and nuclear energy, and penalize those that don’t. It is designed to get 80 percent of the country’s electricity from clean sources by 2030, up from 40 percent now.

A spokeswoman for Mr. Manchin, Sam Runyon, said the senator “has long acknowledged the impacts of climate change in West Virginia. That is why he’s worked hard to find a path forward on important climate legislation that maintains American leadership in energy innovation and critical energy reliability.”

Others say that by blocking efforts to reduce coal and gas use, Mr. Manchin risks hurting his state.

“Not having a credible policy in the U.S. makes it nearly impossible to negotiate real change at a global scale,” said Evan Hansen, a Democratic state representative. “What that means is that West Virginians are going to continue to face greater and greater impacts from climate change.”

Schools, power stations and businesses at risk

The new flood data comes from the First Street Foundation, a nonprofit that uses more granular techniques to gauge flood risk than the Federal Emergency Management Agency.

First Street measures risk not only from rivers but also from smaller creeks and streams — the sort of waterways that expose towns like Farmington to so much flooding, yet are generally left off FEMA’s flood maps.

First Street calculated the portion of all kinds of infrastructure at risk of becoming inoperable because of a so-called 100-year flood — a flood that statistically has a 1 percent chance of happening in any given year. The group compared the results for every state except Alaska and Hawaii. In many cases, West Virginia topped the list.

Sixty-one percent of West Virginia’s power stations are at risk, the highest nationwide and more than twice the average. West Virginia also leads in the share of its roads at risk of inundation, at 46 percent.

The state also ranks highest for the share of fire stations (57 percent) and police stations (50 percent) exposed to a 100-year flood.

And West Virginia ties with Louisiana for the greatest share of schools (38 percent) and commercial properties (37 percent) at risk.

“The geography and topography of the state results in many homes, roads and pieces of critical infrastructure being built along rivers, around which we show extensive flooding,” said Michael Lopes, a spokesman for First Street.

But topography isn’t all that raises West Virginia’s flood risk. Surface mining for coal has removed soil and vegetation that once absorbed rain before it reached creeks and rivers, and has pushed rocks and dirt into those waterways, making them less able to contain large volumes of water.

“As the stream corridors fill up with sediment and debris, there’s simply less storage capacity,” said Nicolas Zegre, director of the West Virginia University Mountain Hydrology Laboratory. “It takes less water to spill over.”

Flood, repair, repeat

The effects of increased flooding can be seen where Mr. Manchin built his political career.

Just northeast of Farmington is Morgantown, where houses perch on narrow streets that wiggle down hillsides, intersecting at erratic angles. Mr. Manchin represented the city in the State Senate; it’s also home to West Virginia University, his alma mater.

In June, Morgantown got more than two inches of rain in less than an hour, according to Damien Davis, the city’s director of engineering and public works. It turned a main thoroughfare, Patteson Drive, into a river and reversed the flow of sewers, pushing waste into basements.

In July it happened again: The city got more than three inches of rain in an hour, Patteson became a river, and raw sewage rushed into basements.

“We had never experienced anything like that,” Mr. Davis said.

Muhammet Ariturk owns a small restaurant, Istanbul, on Patteson Drive. He blocked his doors, but his restaurant flooded both times. “We started trying to stop the water coming here, but we couldn’t,” he said.

A mile north, Mary Anne Marner lives in a white bungalow near a creek. The first flood sent sewage into her basement, ruining her husband’s recliner, among other damage.

“The sewage came up out of the bathtub and out of the toilet,” she said. Ms. Marner and her husband replaced the recliner. Then the basement flooded again, and out went the new recliner.

Kevin Law, the state climatologist, said research showed “an increase in extreme precipitation across West Virginia,” the result of a changing climate.

‘It puts nothing but fear in you’

Twenty miles southeast is Tunnelton, where Dave Biggins owns a convenience store in a building constructed on top of an underground creek. Until recently, the creek rarely rose high enough to damage the foundation — maybe once a decade, Mr. Biggins guessed.

Then, two years ago, the equipment space under his store flooded three times in a single year. That was nothing compared with last month, when the remnants of Hurricane Ida left his store in knee-deep water, causing as much as $80,000 in damage.

“After this, every time it says it’s going to rain pretty hard, it puts nothing but fear in you,” said Mr. Biggins, who lacks flood insurance.

East of Tunnelton is Terra Alta, one of the highest towns in Preston County. In September, heavy rains put three inches of water inside Terra Alta’s town hall and flooded a handful of basements in town, according to James Tasker, the mayor.

“It comes through the wall,” Mr. Tasker said. “It’s our drainage system, which we can’t afford to update.”

Half an hour south, Eric Bautista, the mayor of Rowlesburg, is trying to find money to rebuild the town’s outdated storm water system, which releases raw sewage into the Cheat River during downpours. “It’s a lousy system that is extra lousy when there’s any rain,” Mr. Bautista said.

The consequences reach beyond the county, according to Amanda Pitzer, executive director of Friends of the Cheat, an environmental nonprofit.

“This water goes to Pittsburgh,” Ms. Pitzer said, standing at the Cheat’s edge recently. “You have to think downstream.”

‘That’s the risk we’re willing to take’

After West Virginia was hit by particularly severe flooding in June 2016, it created a state resiliency office to help protect against future flooding.

But earlier this year, the head of that office left. He was replaced by his deputy, Robert Martin Jr., who during a hearing before state lawmakers last month compared the role to drinking from a fire hose.

He wants to update the state’s flood protection plan. “It hadn’t been looked at in around 20 years,” Mr. Martin said. “A lot of the things were really antiquated in it.”

Mr. Martin didn’t respond to requests for comment. The state declined to make any officials involved with disaster recovery or resilience work available for an interview.

Stephen Baldwin, a Democratic state senator whose district was devastated by the 2016 floods, said the state has moved too slowly. The sluggishness reflects the political taint attached to global warming, he said.

“Nobody wants to talk about the real driving factor here, which is the climate,” Mr. Baldwin said.

As flooding gets worse, West Virginia’s leaders, including Mr. Manchin, should stop viewing the state’s identity as tied to coal, said Jamie Shinn, a geography professor at West Virginia University who focuses on adapting to climate change.

“I don’t think he’s defending the future economy and viability of this state,” Dr. Shinn said. “The state has so much potential beyond fossil fuels.”

That point of view remains a tough sell for many West Virginians, despite repeated disasters.

“I’m a big advocate for using the natural resources that we have,” said Jim Hall, the Farmington resident and cousin-in-law of Mr. Manchin’s.

Forced to choose between burning less coal or suffering through worsening floods, he said worsening floods were the lesser danger.

“You can replace a house,” Mr. Hall said. “That’s the risk we’re willing to take.”