Why ‘storm surge’ is one of the biggest threats to Beaufort County during a hurricane

The National Weather Service wants you to understand storm surge. They have pictures

This video provides an explanation of storm surge. Storm surge is what officials use when determining who to evacuate, following the axiom "run from water, hide from wind".
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This video provides an explanation of storm surge. Storm surge is what officials use when determining who to evacuate, following the axiom "run from water, hide from wind".

Editor’s note: In a press conference Tuesday morning, South Carolina Gov. Henry McMaster lifted the mandatory evacuation for Beaufort, Jasper and Colleton counties. To read more, click here.

Hurricane Florence — a Category 4 storm predicted to make landfall in North Carolina on Thursday night or early Friday morning — may bring “life-threatening” storm surge with it, according to the storm surge unit of the National Hurricane Center.

According to the center, storm surge is one of the biggest threats during hurricanes.

“Storm surge — especially along the north and center of the storm — is the primary concern,” said Neil Dixon, a meteorologist at the National Weather Service in Charleston. “For Hilton Head, storm surge is a concern. And the impacts of the wind and rain of the storm could cause quite a bit of damage.”

“Storm surge” is water that pools before a storm and is different from the regular tides, Dixon said. Although, a high tide could add another 6 to 6.5 feet of water to a storm surge.

“Storm surge is produced by water being pushed toward the shore by the force of the winds moving cyclonically around the storm,” according to the National Hurricane Center’s website.

The potential storm surge depends on many factors, according to the center. One of those is the width and slope of the continental shelf.

“A shallow slope will potentially produce a greater storm surge than a steep shelf,” the center says. “For example, a Category 4 storm hitting the Louisiana coastline, which has a very wide and shallow continental shelf, may produce a 20-foot storm surge, while the same hurricane in a place like Miami Beach, Fla., where the continental shelf drops off very quickly, might see an 8- or 9-foot surge.”

Dixon said storm surge models for Hurricane Florence will not come out until a hurricane watch is issued, which is likely to happen Tuesday morning. But it has the potential to impact Beaufort County, even without directly hitting the area.

To see how storm surge might affect you, click here.

Dixon said in Tropical Storm Irma, which hit on Sept. 11, 2017, storm surge was recorded at 12.24 feet at Fort Pulaski, at the mouth of the Savannah river. For Hurricane Matthew, which hit Oct. 8, 2016, storm surge was 12.56 feet. Numbers specific to Hilton Head are not available.

Flooding from the storm surge was seen across the county during Irma.

Hilton Head also took a hit. Some communities were impacted more than others, such as Sea Pines and Wexford.

Harbour and Fripp Islands were also impacted.

Although Dixon could not provide estimates on how much storm surge the county could have with Florence, he could provide estimates for hurricanes in general.

The following storm surge estimates are based on a storm hitting Hilton Head directly, traveling northwest at 15 mph.

Category 1

Harbour Town: 7.3 feet

Some tidal creeks: 8.5-9 feet

Beaches: 4-5 feet

Category 2

Harbour Town: 11.1 feet

Some tidal creeks: 13 feet

Beaches: Between 9-10 feet

Category 3

Harbour Town: 15 feet

Some tidal creeks: Just under 17 feet

Beaches: 12-14 feet

Category 4

Harbour Town: 18.6 feet

Some tidal creeks: 20.7 feet

Beaches: 13-17 feet

Category 5

Harbour Town: 21.8 feet

Some tidal creeks: 24 feet

Beaches: 18-20 feet.

Dixon noted the entirety of Hilton Head Island would be covered in several feet of water with a Category 5 storm.