The official map laid it out for more than 200 homes within the community of Mexico Beach, Florida: the federal government had characterized their flooding risks as minimal, despite their near-beachfront locations.

That meant for them there were no requirements to buy flood insurance, and local residents say many did not.

When Hurricane Michael and its 155-mile-per-hour winds slammed into the town on Oct. 10, with a storm surge of perhaps 19 feet, the result was devastation. An analysis by coastal geologists from Western Carolina University has found that 70 percent of the homes were demolished. Another 10 percent were severely damaged.

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Mexico Beach turns out to be a vivid example of how FEMA's flood maps—part of the troubled National Flood Insurance Program—are failing millions of Americans who own property in low-lying areas along coastal zones, rivers or streams. The problems are made worse as more people build in risky areas and as FEMA fails to factor in how global warming is changing the climate.

"There is tremendous uncertainty in the accuracy of the mapping of these areas," said Andy Coburn, the associate director of the Program for the Study of Developed Shorelines at Western Carolina University. "It almost provides a false sense of security in terms of allowing people to understand what their flood vulnerability is."

Hurricane Michael struck Mexico Beach, Florida, with 155-mile-per-hour winds and a storm surge of as much as 19 feet. It destroyed or severely damaged about 80 percent of the homes. Newer construction, particularly homes built for hurricane conditions and on higher ground, tended to fare better. Credit: Joe Raedle/Getty Images

Scientists have shown that the frequency of the most intense tropical storms is increasing and that global warming caused by the heat-trapping gases humans release from activities like burning fossil fuels can exacerbate extreme weather and contribute to sea level rise that worsens storm surges. A warmer atmosphere also holds more moisture, so storms can dump more rain.

Mexico Beach is on the Gulf of Mexico in Bay County, which last revised its Federal Emergency Management Agency flood maps in 2009, based on a maximum storm surge of 10 feet. County officials are working on revisions but declined to be interviewed. A spokeswoman referred questions to FEMA.

"An individual storm, particularly a major storm like Hurricane Michael, may cause flooding in areas beyond the high-hazard areas" identified on FEMA flood maps, FEMA said in a written response.

Real-Life Consequences When Flood Maps Miss the Mark

The accuracy of FEMA's flood maps has been called into question before. The maps are used in the 22,000 communities that participate in the National Flood Insurance Program to determine which coastal or inland properties must have flood insurance and to set rates.

They cover shorelines and low-lying areas near rivers and streams, and a Department of Homeland Security Inspector General's report last year found that many maps may not reflect actual flood risk or are out of date.

"Without accurate floodplain identification and mapping processes, management, and oversight, FEMA cannot provide members of the public with a reliable rendering of their true flood vulnerability or ensure that (National Flood Insurance Program) rates reflect the real risk of flooding," the report concluded.

Mexico Beach illustrates the real-life consequences of mapping that misses the mark.

"We were fortunate enough to listen to our insurance agent, so we have a (flood) insurance policy," said Susan Whiten, whose home in a nearby coastal community was also in the same minimal risk zone, called "X," and suffered extensive damage from the storm surge. Living out of a camper now, Whiten said she knows a lot of people in Mexico Beach, and many did not have flood insurance.

"They didn't think they'd need it because they were in the X zone," said Whiten, who runs a plumbing business with her husband, Bud.

Bud Whiten surveys the damage after Hurricane Michael struck Mexico Beach, Florida. Credit: John Moran

Mexico Beach, with a population of about 1,200, was largely destroyed by Hurricane Michael. Many of its homes were older, stucco-covered cinder block homes built on concrete slabs, dating to the 1950s. A lot of its residents lived there year-round and worked in the community in seasonal jobs, serving food or drinks in bars and restaurants, or on fishing boats, Whiten said.

"The sad thing is for a lot of these folks, they won't be able to rebuild because of the construction costs," said architect Fred Etchen, who owns a construction and property management business near Mexico Beach.

Rebuilding would be hard enough for many people, even with insurance, but newer building codes that require stronger materials and elevating living quarters on pilings could price many residents out of the market, fundamentally changing the community, Etchen said.

"It's going to be a different world," he said.

Mexico Beach, Before and After the Hurricane

The Western Carolina University team closely tracks how hurricanes affect developed coastal areas in the Southeast. Coastal geologists Blair Tormey and Katie Peek decided to compare the destruction with the FEMA flood maps after they saw an aerial video of Mexico Beach after the Hurricane.

They looked at Google Earth images to determine what the community looked like before, and at the flood risk maps. The minimal-risk zone, X, represents areas where the odds of flooding would be remote, less than 0.2 percent chance of occurring in any year, or what's commonly known as a 500-year flood. Those homes ranged from about 6 to 17 feet above sea level, Tormey said, with some as close as a lot or two away from the shoreline.

Some homeowners returned to Mexico Beach to find little more than their home's foundations remaining. Credit: John Moran

Using information from the U.S. Geological Survey, the team estimated that the storm surge in Mexico Beach must have as reached as much as 19 feet above average sea level, likely a record for Florida. Waves would have added several more feet, they said. The National Weather Service, which measures storm surge from ground level instead, has not yet confirmed its measurements.

Hurricane Michael wiped out much of the city's infrastructure, as well. Credit: John Moran

"We saw some homes that survived," Peek said. "They looked brand new or had deep pilings and expensive construction."

Tormey asked: "Is the price of living at the beach now, in order to stay at the oceanfront, you have to have a fortress and a lot of money?"

But with sea level rise, the shoreline is still moving landward, so just rebuilding stronger isn't necessarily the answer either, he said.

That the maps were so inaccurate suggests they need to be revised again, with more of the area in zones requiring flood insurance, the researchers said.

FEMA, in its written response to InsideClimate News, said it would collect information about Hurricane Michael to incorporate into future mapping.

Millions More Americans Are Exposed

FEMA said it had spent $200 million in recent years updating the maps, including those for coastal areas.

"With the high concentrations of people and economic activity along our nation's coasts, it is vital that residents and businesses in these communities have accurate flood hazard information, know their flood risk, and take steps to reduce the risk to their lives and property," the agency said.

The hurricane and storm surge knocked some homes off their raised foundations. Credit: Joe Raedle/Getty Images

But a study published in February showed that the FEMA maps are missing the mark for tens of millions of Americans. More than 40 million Americans are exposed to serious flood risk at the 100-year-flood or 1 percent level, roughly three times more than appear on FEMA's flood maps, the study in the scientific journal Environmental Research Letters concluded.

With continued development in low-lying areas and climate change, the situation will only get worse, that study found. It identified Florida as a hotspot, with $714 billion in flood-prone properties at risk.

And late last year, the Inspector General's report found that only 42 percent of the FEMA maps were up to date. A report by Bloomberg found some of the maps to be as old as from the 1970s.

The Inspector General's Office blamed the inadequate mapping on a lack of uniform, centralized policies, failure to properly oversee contractors doing the technical work and poor financial management. The Western Carolina University team said there are problems in some areas with poor information about land-surface elevations, and there can be local political pressures to keep properties out of high-risk flood zones because of their insurance requirements.

FEMA's Maps Fail to Reflect Climate Change

Working with local communities, the maps are created by looking at ground elevations and the area's history of storms and flooding.

The National Flood Insurance Program, which includes the FEMA flood maps and insurance payouts—sometime for properties that are repeatedly damaged because of their low-lying locations—is $20.5 billion in debt. That's even after Congress in 2017 cancelled $16 billion of the program's debt so FEMA could pay claims after the destruction from Hurricanes Harvey, Irma and Maria that year. In July, Congress reauthorized the program, but only through Nov. 30.

Yet even as scientists learn more about hurricanes and climate change, FEMA flood-risk mapping does not take into account how global warming is changing the climate, including how sea level is rising.

Much of Mexico Beach, Florida, was left in rubble after Hurricane Michael stuck. That included areas considered to be minimal risk in FEMA's flood maps. Credit: Joe Raedle/Getty Images

It's a mistake to only look back in time, said Larry A. Larson, an engineer and the director emeritus/senior policy advisor for the Association of State Floodplain Managers.

"We know that storms are getting more intense now, especially in the last ten years," Larson said. "What FEMA does not yet do, and flood maps do not yet do, is reflect what they expect future conditions to be."

FEMA did not answer why it fails to consider climate change in developing its flood maps.

Instead, the agency said people can find information on how "flood risks may change in the future" from local and regional planners, state agencies and other federal agencies.

But by ignoring climate change, Larson said, "the day you issue the maps, they're obsolete."

Top photo: Mexico Beach after Hurricane Michael. Credit: Hector Retamal/AFP/Getty Images