News Release

UF engineer: new method predicts severity of hurricane-driven waves

Peer-Reviewed Publication

University of Florida

GAINESVILLE, Fla. --- As Hurricane Alberto churns in the open Atlantic, a University of Florida coastal engineering professor says he has developed a new method to more accurately estimate the severity of waves near shore during hurricanes.

Michel Ochi, a UF professor of civil and coastal engineering, said the results of his method, which is based on wind speed, will help engineers design more hurricane-ready buildings near and on shore. It will also help government officials make more effective rules and regulations regarding coastal development, such as where to forbid or allow development along the beach, Ochi said.

"My methodology advances our ability to come up with a prediction for sea severity at the time of the time of hurricane landfall," said Ochi, who developed the method as part of a recently completed study funded by Florida Sea Grant. "The results may help in the management decision-making for government planners and insurance companies."

When evaluating the condition of the sea near shore at hurricane landing, experts consider three contributing factors: storm surge, tide and waves. Prediction of storm surge and tide have been studied extensively, but the experts had long used a simple method to predict wave conditions. Ochi's method, by contrast, accounts for numerous factors, including how waves change when they move from deep to shallow water, the effects of water depth and the wave breaking process.

The method highlights the importance of the slope of the ocean bottom near shore in depths of 8 meters or less, with steeper slopes tending to result in bigger waves.

With a depth of 8 meters only 500 meters offshore, Panama City appears most vulnerable to severe hurricane-driven waves of any Florida city, the results of the study show. Less vulnerable are Miami, where depths reach 8 meters about 3 kilometers offshore, Tampa, where 8-meter depths lie 4 kilometers offshore and Cedar Key, where depths hit 8 meters about 30 kilometers offshore.

Ochi emphasized, however, that although it is often overlooked, tide level at hurricane landing can greatly influence sea condition, making these generalizations problematic. "The sea condition when a hurricane hits Miami at high tide may be worse than if one hits Panama City at low tide," he said. "Thus, officials must evaluate sea condition at the time of hurricane landing on a case by case basis."

Craig Fugate, chief of preparadness and response for the Florida Division of Emergency Management, said Ochi's study highlights the need for planners to take anticipated wave action into account when preparing for hurricanes. Part of the reason damage in the Panhandle was so significant during Hurricane Opal in 1996 was the strength of the waves generated by the storm, he said.

"I think it probably brings some attention to the fact that in coastal development, the storm surge may not be the only hazard you're facing -- you also have to look at wave action," Fugate said.

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Florida Sea Grant, headquartered at UF, is a partnership program of the State University System and the National Ocean and Atmospheric Administration. Its mission is to foster a sustainable coastal economy and environment through education, extension and research.

Source: Michel Ochi, ochi@coastal.ufl.edu


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