Early surveys of Hurricane Ian’s damage and data from flood sensors show that the massive cyclone’s storm surge — powerful floods of ocean water above normally dry land — rose one to two stories high across some 60 miles of Florida’s southwestern coastline and in some spots spread several miles inland.
Even though early fears of floodwaters surging up Tampa Bay did not come to pass, the findings appear to substantiate dire warnings from the National Weather Service that life-threatening and destructive storm surge would extend far from Ian’s unpredictable landfall point, which ended up on a barrier island near Cape Coral.
Well south of there, in Naples, Marco Island and Everglades City, surveys have shown that ocean waters rose more than seven feet, although damage was less significant, according to data compiled by the U.S. Geological Survey.
“It was a huge surge,” said Jeffry Evans, the meteorologist in charge of the National Weather Service’s Houston/Galveston forecast office, who traveled to Florida to gather the data.
Evans said he saw evidence in two-story condominiums of as much as 15 feet of water washing through northern Fort Myers Beach — a level he said doesn’t include the height of waves that pounded even higher.
About 40 miles away in Marco Island, surveys and data suggest floodwaters rose to 7.5 feet, probably as a result of the surge that Ian’s winds pushed along the shore as the storm churned through the Gulf of Mexico toward landfall, said Ronald Busciolano, a USGS hydrologist and the leader of the agency’s coastal storm team.
“It was a very large storm,” Busciolano said. “The surge was following it and coming up with it.”
Had Ian tracked even slightly farther to the north, “Tampa would have gotten hit much harder,” he said. “They got spared because they were on the north side of the storm.”
Brian LaMarre, the meteorologist in charge of the Weather Service’s Tampa Bay forecast office, said he hopes Ian’s impact prompts those who avoided its most severe conditions to remember what could have been — and, in the future, to pay attention not just to a storm’s expected track, but also areas facing storm surge and other threats, too.
“I think a lot of people here realize how close they came from a deadly, devastating, life-changing hurricane,” he said.
Official data on flooding by the storm surge is not expected for weeks, after more damage surveys have been conducted and the data is reviewed for errors and bias. National Hurricane Center officials said their thorough review of forecasts and observations of Ian would not be completed until the winter or spring.
But preliminary observations show what meteorologists had feared: that surge would be widespread and devastating in areas where Ian’s winds blew toward shore. Because tropical cyclones rotate counterclockwise in the Northern Hemisphere, that meant areas to the south of Ian’s eye were subject to its storm surge.
It was true even in the Florida Keys, which received only a glancing blow from the storm but still recorded water levels several feet above normal. In Key West, a USGS gauge installed ahead of Ian’s arrival showed a 4.5-foot rise in ocean levels.
In the Tampa Bay region, on the other hand, Ian’s more southerly track and its circulation meant that winds pushed water away from shore. A USGS gauge in Clearwater Beach showed a four-foot drop in water levels in what are known as blowout tides or negative storm surge.
The preliminary data comes from a combination of USGS gauges, flood sensors and observations gathered during damage surveys.
The latter involve combing the destruction for signs of water height that look like a bathtub ring. Measurements can come from observations of debris piled up on a shore or lines left on or in buildings by mud or floating seeds. They can appear most sharply in places like bathrooms, closets and inside cabinets, Evans said — places where water can flow in but where wave action is minimal.
That was, at times, hard to find in places like Fort Myers Beach, he said. In many cases, the storm gutted buildings of drywall and left little but debris in its path.
“The extent of the damage was some of the most extreme I’d ever seen,” Evans said.
Some high surge values on Fort Myers Beach from yesterday’s survey. Over 15 foot high still marks above ground on the second floor. Most areas between 10-12’ above MHHW. Complete inundation of the island. #HurricaneIan @JeffLindner1 @NWSTampaBay pic.twitter.com/Ba8WtvkW7p— Jeff Evans (@jeffryevans) October 11, 2022
USGS data analyzed so far shows the surge rose as high as 13.23 feet in Fort Myers Beach, a level that translated to more than nine feet of ocean water above normally dry ground in buildings that sit a few feet above sea level. More data will be collected and more surveys conducted over the next couple of weeks, Busciolano said.
The data also shows storm surge reached well inland in many areas. For example, an estimated nine-foot storm surge meant a foot or two of water spread miles inland in areas like Punta Rassa and Bonita Springs.
The topography in downtown Naples, on the other hand, prevented about eight feet of storm surge from penetrating more than a couple of blocks inland, Mark Bove, a meteorologist who participated in damage surveys and is the senior vice president for natural catastrophe solutions for the insurance company Munich Re US, said in an email.
Water levels rose more than seven feet in the Caloosahatchee River that separates Cape Coral and Fort Myers, as measured some 20 miles inland from the gulf. That is probably a product of heavy inland rainfall as well as the storm surge, Busciolano said.
“Water is going to want to find its level,” spilling into whatever low spots it can find, he said. “It’s going to keep pushing upstream … and gets further inland than you would think.”