Main Street flooding drone pic

Main Street in Conway, looking towards downtown Conway, after the Waccamaw River and Crabtree Swamp flooded the area in the aftermath of Hurricane Florence. 

Wayne Wardien watched the water climb to his front steps during the great flood of 2015.
A year later, he pulled up strips of new bamboo flooring ahead of Hurricane Matthew’s flood, the first to breach the Socastee home where the Minnesota transplant has lived for nearly a quarter century.
But last month was the worst. As Hurricane Florence crept over the Carolinas, the storm’s agonizingly slow downpours led to flooding across both states. It sent four feet of the Intracoastal Waterway into Wardien's house.
“Whoever heard of a damn hurricane moving at two miles an hour?” he said.
That’s exactly the question a Coastal Carolina University professor wants to study. Len Pietrafesa, who heads Coastal Carolina University’s Hurricane Genesis and Outlook Project (HUGO), is pursuing a federal grant to research how large, drenching storms cause disastrous inland flooding. Think Hurricane Joaquin in 2015, Matthew in 2016, Harvey last year and Florence last month.
“Why is there so much flooding with these new storms?” said Pietrafesa, a physicist and research scholar at Coastal . “It’s not just the precipitation.”
Pietrafesa does have a theory — one he’s been talking about for nearly 20 years. 
In 2000, he gave a talk to forecasters from the National Weather Service.
At the time, he chaired the National Oceanic and Atmospheric Administration’s (NOAA) Science Advisory Board. He’d been asked to speak about Hurricane Floyd, which had caused devastating flooding in the Carolinas the previous year.
Floyd ultimately killed 74 people, including dozens in eastern North Carolina.
Shortly before he gave his speech, Pietrafesa read a report NOAA had recently published. That document focused on Floyd, but it never mentioned Hurricane Dennis, which preceded Floyd by a few weeks. Dennis was a drenching storm that sat off the coast for days. The hurricane caused the Pamlico and Neuse rivers to overflow.
That flooding interested Pietrafesa, who found that water from hurricanes had historically been deadlier in North Carolina than high winds.
Specifically, Pietrafesa was intrigued by the way rivers flooded. Rather than accepting the traditional wisdom that surge from a storm caused a flood, he noticed something he hadn’t seen mentioned in other research.
He was increasingly seeing larger, slow-moving hurricanes that fed off the warm water coming from the Gulf Stream.
“It’s the size,” he said. “Not so much the intensity, but the size of the storms. The winds aren’t necessarily stronger, but the windfields are wider. … So they cover more in the horizontal plane.”
His theory is that as these massive, creeping storms approach the East Coast, each builds a wall of water. When that water arrives at the mouths of rivers, it creates a natural dam. At the same time, the storm dumps rain over the same areas as it makes its slog inland. Unable to relieve themselves, the rivers quickly gush over their banks.
“You get explosive lateral flooding,” Pietrafesa said. “When [the river] can’t go up anymore, it can only go out. And because the coastal plains are so flat, it doesn’t take four to five hours to flood a city. It can take 20 minutes to an hour. … because the rivers can’t rise anymore. They can only go out.”
Local officials often insist that the area has historically seen two types of flooding — flash flooding that comes from heavy rains overwhelming drainage systems and river flooding that stems from floodwaters flowing down from North Carolina and sending the Waccamaw and Little Pee Dee rivers over their banks.
“These are things we can actually design for,” Horry County Councilman Johnny Vaught said at a recent council meeting, referring to flash flooding. “But when the good Lord sends all that river water towards us and all that kind of thing, that’s not something we can control.”
But in Pietrafesa’s theory, a lethargic, massive hurricane can create a hybrid flood where a storm’s slog through an area simultaneously causes flash flooding while keeping the rivers overflowing.
With Florence, he pointed to the Cape Fear River in North Carolina as an example.
“You back the systems up,” he said. “You literally just put a cork in and you back them up. That process has never been studied.”
Pietrafesa's peers didn’t show much interest in his idea 18 years ago, and he hasn’t seen any research since that looks at this particular theory of flooding.
But he said it’s important to understand how these storms work and the potential impacts along the Grand Strand.
“It literally connects the mouths of the harbors, the estuaries and the rivers to the heads of the rivers,” he said. “You’ve got to study everything in between. It’s a whole system.”
His colleague at Coastal, Paul Gayes, agrees that the way communities understand and prepare for hurricanes must change. Gayes is a marine science professor and the director of Coastal’s Burroughs & Chapin Center for Marine and Wetland Studies. 
“Climate has been a really challenging concept,” he said. “Because it’s always this long-term thing and we have the immediacy of many, many problems that are expensive and rather important. So it’s been something that’s been easy to kind of push back and make a secondary or tertiary concern. But I think [with] what’s been happening in the last couple years, I think people are seeing things that are different from the way the systems worked in the past. And I think there’s a lot of data that supports this.”
He points to NOAA figures showing that since 1980 there have been 238 weather events in the United States that caused at least $1 billion in costs/damage. Last year, weather-related impacts to the United States exceeded $300 billion — a new high that amounts to about 25 percent of the country’s discretionary budget.
Gayes concedes that population and development factor into those numbers. More people and infrastructure mean more is at risk. But that doesn’t explain everything.
“The fact is, if you look at the data over the last 30 years, it’s clearly been jumping up the last five to 10,” he said. “It’s really hard to say that this isn’t a change in the system.”
But how should officials respond? For starters, Gayes said, the way storms are classified should change.
Rather than focus on wind speed, which is what Saffir–Simpson scaleuses to categorize hurricanes, he said broader impacts should be considered.
“That doesn’t totally describe what you’re going to experience,” Gayes said. “Category 4 is a wind velocity only. … In and of itself, that word is not very descriptive. The winds aren’t the only thing. It’s the surge and the rainfall and all that. So there’s a need for more complete information and that information can be really complex. And how do you get that information that’s complex and communicate it well? That’s one of the challenges that’s out there. I think that’s what we’re really trying to focus on.”
Another concern for Gayes is the process for flood planning. Typically historical data is used to make projections for future disasters.
“It’s based on the past behavior and the last 100 years,” he said. “If the system’s changed, then the past behavior is no longer as good an indicator of the future. And that’s where we have a huge vulnerability and exposure. … We’re almost challenged now to have to go into more of a physics-based model. We almost have to understand how the system’s really being driven on a scale from global down to local.”
But the response should involve more than just an academic understanding of the problems, Gayes said. Recent storms have shown the need for public officials to view climate issues through the prism of economic, energy and national security policies. That could mean different ways of handling beach renourishment or zoning.
“It’s an opportunity,” he said. “There’s a willingness to, if not recognize, begin to consider the possibility that the status quo approach to these problems is not going to be viable long term.”
How local, state and federal officials respond to these changes remains to be seen. They are, however, acknowledging that continuing to rebuild flooded communities and hoping for the best is unwise.
“We’re not going to keep doing this,” said U.S. Sen. Lindsey Graham as he toured Wardien’s Socastee neighborhood last week. “It’s not fair to people. It’s dangerous. And it’s time to make some good, hard decisions for the people who come after us. People argue about climate change. I can tell you: something’s going on out there. These storms are getting more fierce. They’re more frequent. The water’s getting warmer. … There is no magic answer, but I do promise you, along with everybody else here, that the hard decisions we’ve ignored can’t be ignored anymore.”

Contact Charles D. Perry at 843-488-7236


I'm the editor of and the Carolina Forest Chronicle, a weekly newspaper in Horry County, South Carolina. I cover county government, the justice system and agriculture. Know of a story that needs to be covered? Call me at 843-488-7236.

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