Home Inspection in Seabrook Island, SC

Deveaux Bank was born from the sea, and to the sea it shall someday return.

The tiny sand bank is located off the southern tip of Seabrook Island, at the mouth of the North Edisto River. Deveaux is about 215 acres, according to the S.C. Department of Natural Resources.

Well, sometimes it is. Deveaux's size fluctuates, the department notes. Like South Carolina's other islands, Deveaux grows and shrinks as it accumulates and loses sand.

That lifecycle can offer important lessons for coastal South Carolina's future as rising seas, a changing climate and booming development increase pressure on the state's barrier islands.

South Carolina's islands run the gamut from small spits of land to massive barrier islands that host their own communities — think Hilton Head, Folly Beach or Pawley's Island. They provide habitat for sea turtles, migratory birds and other wildlife. Deveaux Bank, for example, is a critical stop-over point for migratory birds, and access to the island is off-limits to humans during the spring and summer shorebird nesting season.

The islands also protect communities further inland from hurricane storm surge, according to DNR — which is why they're often referred to as barrier islands.

They're formed by the southward movement of sand along South Carolina's coast and sculpted by wind and waves, according to DNR.

That sand easily can be washed away. Katie Luciano, a coastal geologist with DNR, calls the coast's smaller islands "ephemeral" because of their relatively short life cycles. Hurricanes can erode years of accumulation overnight, and even an above-average king tide can suck away a sizeable chunk of an island's land mass.

But rebirth is a possibility and appears to be a part of some islands' natural lifecycle, Luciano said.

"During (1979's) Hurricane David, Deveaux Bank essentially completely disappeared," she said, although the bank was reconstituted a few years later. Luciano said Deveaux appears to have a cyclical lifecycle of about 40-50 years.

"This is a feature that's been mappable since the mid-to-late 1800s," she said. "It has a really dynamic nature to it."

That lifecycle might soon be disrupted.

South Carolina is predicted to experience about a foot of sea level rise by 2050, according to estimates from the National Oceanic and Atmospheric Administration. That presents a huge problem for the barrier islands, which typically only sit a few feet above of the ocean.

As those base water levels rise, king tides are washing further inland. The higher-than-average high tides occur about half-a-dozen times a year in cycles that can last anywhere from a single day to nearly a week. They're infamous for flooding downtown Charleston's lowest roads and snarling rush hour traffic in the city.

Part of Luciano's job at the DNR is investigating how enhanced king tides, also known as Perigean spring tides, impact erosion on barrier islands. Her research is ongoing, but her preliminary insights could offer some lessons — namely that higher king tides are limiting the islands' ability to form healthy sand dunes and absorb stronger blows from hurricanes.

"I feel like storms really picked up in 2015, and we've been seeing an increase in higher spring tides," she said.

Charleston has experienced more than 600 flooding tides since January 2015, ranging from minor nuisance puddling to complete washouts, according to the National Weather Service's Coastal Flood Events Database. That federal database goes back more than a century, but 44 percent of all of the city's recorded flooding tides have occurred over the past 10 years — an indicator of the region's rising sea levels.

And nearly three-quarters of Charleston's major tidal flooding events, which severely inundate downtown and the region's other low-lying areas, have occurred in the last decade. Those major tides also can significantly erode local beaches.

That problem is further compounded by another issue — "coastal squeeze." That phenomenon occurs when an island (or, specifically, the sandy beach) gets stuck between a proverbial rock — rising seas — and a literal hard place — human development — and are slowly squeezed out of existence.

"In some of these places ... the sand is maybe getting to the beach, but it's not staying there," Luciano said. "And because it's not staying there, the dunes aren't forming, and the dunes are really indicative of a nice, healthy barrier island."