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Hurricane Helene dumped trillions of gallons of water hundreds of miles inland, devastating communities nestled in mountains far from the threat of storm surge or sea level rise. But that distance can conceal a history of flooding in a region where water races into populated towns tucked into steep valleys.
“We almost always associate flood risk with hurricanes and coastal storm surge in Florida, Louisiana and Texas,” said Jeremy Porter, head of climate implication research at First Street, a company that analyzes climate risk. “We don’t think of western North Carolina and the Appalachian mountains as an area that has significant flood risk.”
More than 160 people have died across six Southeastern states. The flood waters carved up roads, knocked out cell service and pushed debris and mud into towns.
Parts of the Blue Ridge Mountains where fall colors are just starting to peek through were hit especially hard. In tourist-friendly Asheville, officials warned that it might take weeks to restore drinking water. Brownish orange mud stands out on river banks, a reminder of how high rivers swelled.
Hurricanes moving inland with heavy rainstorms have created disaster before. In 2004, for example, four people were killed in western North Carolina from a debris flow caused by as much of a foot (30.5 centimeters) of rain that fell from Hurricane Ivan.
It’s difficult to quickly determine the exact role climate change played in specific disasters like Hurricane Helene although one quick analysis found it likely increased rainfall totals in some areas.
Scientists say global warming is helping some big hurricanes become wetter.
Plus, a warmer atmosphere can hold more water, fueling intense rainstorms, although mountainous Appalachian terrain complicates the interaction between weather events and climate change, according to Jim Smith, a hydrologist at Princeton University.
Dave Marshall, executive pastor at First Baptist Church in Hendersonville, North Carolina, said he was “totally shocked” by the storm’s destruction that overwhelmed local services. On Tuesday he was overseeing a busy donation center that offered essentials such as propane and food, remarking that he had expected some rain and maybe a day or two without power.
“Nobody was prepared,” Marshall said. “We are shocked and devastated. Everybody knows a friend or family member that has lost a loved one.”
Porter, the climate risk researcher, said the Federal Emergency Management Agency’s flood maps used to determine the riskiest areas where certain homeowners are required to purchase flood insurance have their limitations. He said the maps consider a specific range of flooding and underestimate flood risk in some areas — and that the problem is especially pronounced in parts of Appalachia.
“It’s happening more and more often that we’re seeing these heavy precipitation events occur, exactly the type of events that this region is susceptible to,” Porter said, adding that flood zones on FEMA maps aren’t capturing these changing conditions.
FEMA recently updated how it prices flood insurance to factor in more types of flooding to accurately base cost on flood risk. The agency says flood maps are not meant to predict what areas will flood. Instead, they help define the riskiest areas for planning and insurance needs, FEMA said.
“Flooding events do not follow lines on a map. Where it can rain, it can flood,” said Daniel Llargues, a FEMA spokesperson.
Before Helene, federal forecasters told residents in western North Carolina flooding from the hurricane could be “one of the most significant weather events to happen” since 1916. That year, a pair of hurricanes within a week killed at least 80 people, and the community of Altapass received more than 20 inches of rain (50.8 centimeters) in a 24-hour span.
“This is not a big surprise,” said Smith. “But what happened in Helene happened in 1916.”
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Phillis reported from St. Louis.
