Storm surge maps predict widespread flooding in Savannah and Charleston

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Flooding prediction for Savannah, Georgia based on data by NOAA’s nowCOAST™. Photo by Travis Daub

Update, 1:39 p.m. EDT, 10/7: Hurricane Matthew has weakened to a Category 3, but it’s still causing massive storm surges. Its closest approach angled slightly north of original predictions, but areas like Cape Canaveral have recorded winds of 100 miles per hour this morning. In Florida, many streets in St. Augustine are flooded, and heavy rains are pounding Jacksonville. NOAA’s nowCOAST™ models still predict up to three feet of flooding in parts of Jacksonville, Savannah, Georgia and Charleston and South Carolina. The National Weather Service stated the storm’s forecast isn’t due to deviate, so the these predictions are likely to hold firm. Hundreds of thousands have fled the southeast coast.

Hurricane Matthew's arrival may trigger unprecedented flood damage in Florida, Georgia and the Carolinas due to storm surge and sea-level rise. Flood data by NOAA's nowCOAST™. Photo by Travis Daub


Hurricane Matthew is yet to make landfall in the U.S., but the battering has begun. Thousands lost power in Florida’s Miami-Dade, Broward and Palm Beach counties on Thursday, as the storm escalated to a Category 4. Matthew’s 140-mile-per-hour winds now march toward the coast, where Florida Gov. Rick Scott has issued evacuation orders for more than 1.5 million people in 14 counties. Similar coastal evacuations are set for Georgia, South Carolina and North Carolina, which are also in the storm’s path.

Over the next three days, forecasters predict strong winds and storm surges will cause most of the damage. Any storm over Category 3 (that’s sustained winds greater than 111 mile per hour) carries the potential for toppling homes and trees. Meteorologists predict the storm will maintain Category 3 or higher status until it strikes southern Georgia early Saturday morning.

But what about storm surge and flooding?

For an answer, we turned to nowCOAST™, a potential storm surge flooding map created by the National Oceanic and Atmospheric Administration. This model takes data from the National Weather Service and predicts the risk of coastal flooding caused by storm surge. It updates every hour or so, based on dozens of predictions of the storm’s path, and then displays a reasonable worst-case scenario.

In Florida, Daytona Beach and St Augustine are the most populated areas directly in the bullseye of the storm, said Benjamin Strauss, an environmental scientist with Climate Central, and these locations, plus Cape Canaveral and Jacksonville, may suffer some of the the worst flooding. There, the flooding forecasts range anywhere from six to 10 feet. But Strauss said the most severe flooding could occur inland.

St. Augustine and Daytona Beach, Florida reside in Hurricane Matthew's bullseye -- the location where the storm is due to hit at its strongest point. But severe flooding may hit inland rather than along the barrier beaches. Storm surge prediction data by NOAA's nowCOAST™. Photo by Travis Daub
St. Augustine and Daytona Beach, Florida reside in Hurricane Matthew's bullseye -- the location where the storm is due to hit at its strongest point. But severe flooding may hit inland rather than along the barrier beaches. Flood prediction data by NOAA's nowCOAST™. Photo by Travis Daub

St. Augustine and Daytona Beach, Florida reside in Hurricane Matthew’s bullseye — the location where the storm is due to hit at its strongest point. But severe flooding may hit inland rather than along the barrier beaches. Storm surge prediction data by NOAA’s nowCOAST™. Photo by Travis Daub

“When most people think of hurricane of flooding, they think of the beach,” Strauss said. “But beaches have a slope where water can drain. It’s the backside of the barrier island that’s lower and flatter.”

Such is the case for Cape Canaveral, where the Kennedy Space Center is bracing for damage to its $11 billion spaceport.

Strauss cautioned that people should not feel sheltered just because they can’t see the beach, especially in the downtowns of Jacksonville and St Augustine in Florida, Savannah, Georgia, and Charleston, South Carolina. Local surges can happen a good distance from the waves due to inlets or intercoastal waterways.

Hurricane Matthew’s arrival may trigger unprecedented flood damage in Florida, Georgia and the Carolinas due to storm surge and sea-level rise. Storm surge prediction data by NOAA’s nowCOAST™. Photo by Travis Daub“You’ve got situations where water squeezes into these inlets, and the surge can be amplified on a local basis,” Strauss said. “In St. Augustine, you see 10-foot-plus surge levels. Jacksonville would seem to be protected, but the models suggest some amplification of surge right around the inland waterways. The same is true in other places where there are little estuaries.”

Low-lying Cape Canaveral and Kennedy Space Center may be covered by more than nine feet of water due to Hurricane Matthew. Data by NOAA's nowCOAST™. Photo by Travis Daub

The nowCOAST model predicted low-lying Cape Canaveral and Kennedy Space Center could have been covered by more than 9 feet of water by Hurricane Matthew, but the storm stayed off the coast and early reports indicate flooding wasn’t quite so severe. Storm surge prediction data by NOAA’s nowCOAST™. Photo by Travis Daub

On Thursday’s NewsHour, FEMA Administrator Craig Fugate cautioned people to pay close attention to storm forecasts and evacuation warnings.

“There will be a point tonight where it’s too late, people cannot be rescued, they didn’t go in time, they’re going to run out of options,” Fugate told the NewsHour’s Gwen Ifill. “And, unfortunately, that means they may lose their lives. This is all about life safety. That’s why we’re so adamant about getting people to evacuate out of these areas.”

He echoed Strauss that people should not feel protected because they’re not located directly on the coast. Hurricane Hugo, he said, was an example of a storm that caused destructive flooding far inland.

“That’s why it’s important that people heed those evacuation orders, particularly around rivers and the tributaries like the St. John’s, the St. Mary’s, up through the Savannah River and all those basins, because water can travel far inland and cause flooding well away from the coast, if people aren’t aware of it,” Fugate said

Strauss, whose team at Climate Central specializes in sea-level rise, believes coastal destruction with Matthew could be worse than past storms, because of rising sea levels. Global warming has intensified storms over time, and even though ocean levels have only risen an inch or two since the last major hurricane struck the U.S. more than a decade ago, Strauss expects more severe destruction from flooding this time around. That’s because flood damage increases at a sharper rate than the depth of the flood, based on research done by the Army Corps of Engineers, he said.

“Think of how much more damage is done if the water ends up just below your electric socket or just above,” Strauss said. “It’s the difference between having to replace your electric system or not.”

An inch or two may seem a small margin, but Strauss said “you’re still talking about thousands of people who wouldn’t have been flooded.”

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