In Gulfport, Fla., an artsy waterfront city of about 12,000, downed trees and piles of debris line streets that were once neatly flanked by modest pastel homes. Construction crews are a common sight.

Residents are still recovering from Hurricanes Helene, which battered Florida’s Gulf Coast a year ago, and Milton, which hit less than two weeks later. Many have been ordered to completely rebuild damaged homes instead of repair them, upending their lives and changing the small-town feel of a place that was unique in the condo-packed state.

In communities participating in the federal flood insurance program, any home that has been “substantially damaged” must be rebuilt to the latest flood-resistant standards or demolished.

The rule is meant to make cities and towns along the water more resilient. But in Gulfport and other storm-torn coastal communities, it has forced thousands of hard decisions throughout the past year. The cost of compliance was simply too high for some residents, so they sold, often at a loss.

“The locals are disappearing,” said Nancy Poucher, 70, an artist who bought a mustard-colored bungalow in Gulfport with her husband for their retirement. The house flooded badly during Helene, and the cost of rebuilding to code was too high.

These decisions are accelerating what one Florida lawmaker has called “the great reset” of the state’s waterfront after several ferocious hurricane seasons. The colorful cottages that had dotted many towns along the Gulf Coast are giving way to hulking, storm-hardened homes.

“People moved here because they liked the old Florida character,” said April Thanos, the vice mayor of Gulfport. “Whether you call them McMansions or not, the homes that are going to be built are going to be elevated, and larger. It will change things.”

That is what happened in the Lower Keys after Hurricane Irma in 2017, and in Fort Myers Beach after Hurricane Ian in 2022. Only the wealthy may be able to afford to rebuild in compliance, but it is increasingly the only way to live on the coast in the era of global warming.

The troubles in Gulfport stem from a national system that touches more than 20,000 communities enrolled in the National Flood Insurance Program, which the Federal Emergency Management Agency manages. The program offers flood insurance to communities that enforce certain rules — including the one that requires any home found to have “substantial damage” from a storm or flood to be rebuilt to modern code.

Under the rule, “substantial damage” means the cost of repairing the home would exceed half its market value, as determined by local officials.

According to a FEMA document explaining the policy, setting the threshold at 50 percent was “a compromise between two extremes” — balancing homeowners’ abilities to repair or upgrade properties with the need to protect flood-prone areas.

Although the rule has existed for decades, its reach is growing as climate change fuels more powerful and volatile storms. Hurricane Helene, the worst in a century for the Tampa Bay area, flooded Gulfport and surrounding communities that had long avoided such devastation.

FEMA has estimated that buildings constructed to floodplain management standards sustain, on average, 80 percent less damage during floods. Florida’s history with hurricanes highlights the value of these regulations, said Shelton Weeks, a real estate professor at Florida Gulf Coast University.

“When you look at the new properties that were built to current code and were elevated, they’re very resilient,” Dr. Weeks said. “The problem is just the cost.”

Florida officials estimate that thousands of structures sustained significant damage during the back-to-back hurricanes last fall. Helene made landfall about 200 miles north of Gulfport in late September as a powerful Category 4 storm, generating a storm surge that reached all the way to the Tampa Bay region.

Two weeks later, Milton rapidly intensified and hit the state as a Category 3 storm, causing additional deaths and widespread flooding.

Demolitions, often triggered by determinations of substantial damage, have surged in some counties that were hit. In Pinellas County, where Gulfport is, officials have processed about 250 demolition permits for homes in unincorporated areas since October — about four times the number issued during the same period last year. Many additional demolitions have taken place in coastal towns, including 32 in Gulfport.

The sheer scale of the destruction has prompted renewed scrutiny of the rule, with some Florida lawmakers now calling for changes. Representative Anna Paulina Luna, a Republican whose district includes most of Pinellas County, has pushed to waive the rule, calling it an “overreach” by the federal government.

FEMA did not respond to questions about whether the new administration might reconsider or eliminate the requirement. President Trump has reduced the agency’s staff this year and threatened to dismantle it altogether.

In Gulfport, known for its colorful homes, quirky shops and bohemian charm, about 100 homes were deemed substantially damaged. Residents were given a deadline of June 1, the start of hurricane season, to decide what to do with their homes, though some are still fighting the damage determination, according to Mayor Karen Love.

“They’re feeling outrage,” she said.

Stacey Purcell, 63, a real estate agent, said she had heard a steady stream of stories from people trying to sell homes that they cannot afford to rebuild to the higher standards. She started a campaign called “Gulfport Bounces Back,” handing out mini beach balls from the porch of her office, to raise morale.

Diane Hannem, 72, was able to return to her storm-damaged home. She said that throughout three decades of living in Gulfport, she had always felt safe in her house, which was built across from the marina in 1952.

When Helene’s storm surge hit, three and a half feet of water filled her garage. Nine inches of water swelled antique wood furniture and destroyed her vintage Schwinn bicycle, books, clothes and record collection. Her washing machine was afloat.

After the city determined that her home had been substantially damaged, Ms. Hannem faced a difficult decision: rebuild or walk away. Elevating the home was financially out of reach. She stayed in a motel for months, and then rented an apartment while deciding what to do next.

In the end, she was able to restore her home without elevating it, after a reassessment found the damage did not exceed half its market value. After almost a year away, she moved back in just in time for her birthday.

“I’m rolling the dice and hoping we don’t have this kind of situation again,” she said.

Ms. Poucher, the artist who decided to sell her home, said she would have stayed if not for the stringent rebuilding requirements. Her bungalow, with native flowers blooming outside, took in over a foot of water during Helene and suffered wind damage during Milton.

But the cost of elevating the home — estimated at over $100,000 — was beyond reach. Her insurance payout fell short, and she did not receive money from Elevate Florida, a state program that helps residents raise their homes.

She and her husband listed the land for sale and explored more affordable options, including homes outside the state. For several months, they stayed with friends in town. Each day, her husband told her, “I miss bringing you your tea in your hammock.”

Over the summer, they sold the property to a developer for about half of what they estimated it was worth before the storms. It was still enough to purchase another home in Gulfport, this time outside the flood zone.

Ms. Poucher said she knew her old home was in a flood zone when she bought it. “I joked that we would probably be dead by the time the sea level would rise up to where our house was,” she said. Despite her sadness at losing it, she said she’s relieved to know she’s safer from floods.

She now leads a group that paints portraits of homes for residents who have had to demolish or sell them. They have created eight so far and plan to continue once the weather cools down.

A friend surprised her with a painting of her own bungalow. It brought her to tears.