Charleston is experiencing significant coastal flooding from rising tide and rising sea levels

Between 1953 and 2000, Charleston experienced minor flooding an average of eight times per year, according to the National Weather Service. Over the past decade, this number has quintupled to more than 41 instances per year.

Monday’s event was classified as a major flood, a threshold reached only six times between 1953 and 2000 but which has yet occurred eight times in the past two years, according to the weather agency.

“On the satellite, you could see the tide coming in,” said Neil Dixon, NWS meteorologist in Charleston. This is the first time he has witnessed such a thing.

“It was really striking to see some of the swampy areas filling up with water,” he noted. “We reached the coastal flood criteria in minutes [after noon]. Lots of water got in.

Pockets of flooding also concentrated in Westside and Harleston Village, including north of the Medical District and along the Ashley River.

The floods were not limited to the city. Many beaches suffered erosion and rip currents, with water levels just over two feet above normal.

September to November marks a key overlap of factors – including Earth’s proximity to the sun and the position of major weather systems – that now make harmful flooding routine. The fall location of an area of ​​high pressure near Bermuda, around which air circulates clockwise, helps increase onshore winds, while tides are often more dramatic at fall anyway.

The current flood is the result of a trifecta of influences.

“The main drivers of the tide are astronomical forces,” Dixon said. “We just had a new moon and a perigee where the moon passes close to Earth, so those are going to be quite high [tides] anyway.”

The offshore anticyclone also plays a decisive role.

“Then we have this area of ​​ridge, surface high pressure that provided these gusty northeast winds,” Dixon explained. “It’s a known wind direction for high tides. It has been quite persistent towards the northeast for several days, accumulating water along our coast.

Past tropical weather patterns also played a role, as did a pair of tropical systems. The remnants of Hurricane Sally brought heavy rains to the Carolina Piedmont and Virginia Tide, much of which entered river basins and spilled into the sea.

“We have fresh water that is piped [to sea]”, Dixon said. “It’s from Sally. [storm] moved through the western Carolinas and dumped heavy rain. It’s sort of in the drainage area of ​​northern Georgia and western South Carolina. This water is carried by rivers, so we also see some influence of fresh water.

Hurricane Teddy, meanwhile, spent the first part of the week sailing north of Bermuda as it underwent an extratropical transition and targeted the Canadian Maritimes. Waves of 50 feet are likely over waters south of Nova Scotia. These rough seas heightened splash fears and further aggravated coastal flooding across the Carolinas.

“Some waves from Teddy at high tide came up the beach and through the dunes,” Dixon said.

But the biggest contributor to recent coastal flooding has been rising sea levels, leading to regular flooding of coastal areas. Since 1950, the Charleston average the water level has risen about 11 inches. This skewed the odds of flooding towards a disproportionate likelihood, especially for high-end events.

It’s like being a young child and having trouble reaching the kitchen counter. Even if they jump, they may not get there. But over time, the child grows up, and suddenly reaching the counter is not such an impressive feat. Eventually it becomes routine – much like the King Tide floods in the southeast.

In Charleston, major flooding has been 18 times more frequent since 2015 than before, and that number will only increase as seas continue to swell.

“Since the ’90s, there’s been a pretty noticeable upward trend in these events,” Dixon said. “Rising sea levels, some development issues and development closer and closer to water” all play a role, he said.

While such flooding on a sunny day is a nuisance, as sea levels continue to rise and hurricanes grow stronger, the risk of a devastating storm surge causing even more severe flooding along the East Coast is growing.

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