Charleston is sinking while the sea is rising

CHARLESTON, S.C. — Like thousands of others moving to the Charleston region every year, Rick Siebold left his New Jersey home in search of paradise.

“When it came time to get away from the snow, I decided I’d make the move,” he said.

Now he spends much of his retirement fishing, walking, and enjoying the same things that make Charleston one of the top tourist destinations and the fastest-growing cities in the country: its beautifully preserved historic districts, sunny skies, and access to water.

Yet, Siebold is also well aware Charleston’s water comes with a major tradeoff, street flooding.

“It gets deep in some places, you have to leave your car and take your shoes off,” he said.

Sinking land and rising seas

According to Scott Harris, a geology professor at the College of Charleston, nuisance flooding has always been a part of Charleston’s geography, but it’s gotten worse in the past few decades due to two simultaneous issues.

The water is rising and the land is sinking.

“We have land issues, and we have ocean issues,” he said. “And some of that land sinks more than others.”

Ground compaction, or subsidence, is a natural process underway across the entire East Coast, but research out of Virginia Tech found Charleston is one of the fastest sinking cities in the country, with an average rate of around 4 millimeters a year or an inch every six to seven years.

It sounds small on its own, but as the water rises around it, Charleston’s Chief Resiliency Officer Dale Morris says it compounds the impact of the area’s other geological concerns.

“Sea level rise is going to make that even worse going forward,” he said.

Charleston has experienced 13 inches of sea level rise in the past 100 years and Morris said the city expects the water to rise another foot by 2050. With large portions of the peninsula less than eight feet below sea level, every inch counts.

“We have this really complex challenge of how do we stay here,” he said.

‘Water wants to go where water once was’

The best way to understand the city’s future risk is to look at its past. Significant portions of Charleston’s peninsula didn’t exist when settlers arrived more than 300 years ago.

After building up much of the high ground, those settlements expanded over the centuries and where they couldn’t find suitable land, Low Country Hazards Center Director Norman Levine said they made their own.

“All of the marsh and water features that are on the peninsula had to be filled in,” he said. “It all built up within the city then it started to move out into the suburbs, further and further with the development pressures.”

Now, Levine said, those fill areas are some of the fastest sinking spots in the city and the most vulnerable when the tide comes in or rains pour down.

“Water wants to go where water was before,” he said.

The city’s medical district, built entirely on fill, is of particular concern.

“[The buildings] are rooted in the deeper material so they’re very stable,” Harris said. “But the land is sinking around them.”

In 2023, Charleston saw 75 flood events. By 2045, NOAA predicts Charleston will see 180.

Keeping the water at bay

Morris said the city has worked to improve drainage in those vulnerable districts and the Low Country Hazard Center has developed tools to help locals track and predict daily flood threats. Levine said by looking at precipitation and tidal data, the Chucktown Floods portal can predict which streets might close by the end of the day.

“We have to plan our travels around our tides. That happens a lot here,” Harris said. “Every morning when I wake up before I come into work I turn on my apps, I look at Waze, I look at Google Maps just to see what’s going on in case I’m gonna have a ten-minute drive in to work or a three-hour drive in to work.”

Ultimately, Morris said the city is going to need a more permanent solution to manage the near daily threat of high water. The Charleston Peninsula Coastal Storm Risk Management Study determined a $1.3 billion, 12-foot storm surge wall could be the most cost-effective, long-term solution.

“So that it can help us manage storm surge and hopefully help us manage tides too,” he said.

As for Siebold, he said he believes his new home needs to do what it takes to keep people safe, but he said he chose to live by the water and understands the risks.

“Everybody seems to be prepared,” he said. “There’s no perfect place to live.”

If the city is going to do something as dramatic as building a sea wall, he said it has to be done without passing the cost onto taxpayers and without destroying what makes Charleston unique.

“It’s gotta be right,” he said. “It’s quite an undertaking.”

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