'Water is what's killing people': Hurricanes could cause catastrophic flooding in Florida
WEST PALM BEACH, Fla. – Could portions of the Florida peninsula get drenched by catastrophic flooding like Hurricanes Harvey and Florence unleashed the last two years in Texas and the Carolinas?
Yes – and not in the ways you might expect, National Weather Service meteorologists warn.
“We all know the flooding that resulted from Harvey. We've seen the pictures. But it's a tale that could be told easily here in any of the cities of Florida: a Miami, a Tampa, a Pensacola, a Jacksonville. It doesn't matter," said Jason Beaman, NWS warning coordination meteorologist in Mobile, Alabama.
"The same result could be here as it was in Houston," he said.
Beaman helped deliver a presentation Thursday during the Governor's Hurricane Conference at the Palm Beach County Convention Center.
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Floodwater forecasts and warnings are rising to the forefront among emergency managers across the Southeast. When people close their eyes and envision a hurricane, most will conjure wind-related images, National Hurricane Center Director Ken Graham said.
"Water is what's killing people," Graham said during the conference. He cited these statistics:
• 83% of U.S. tropical cyclone fatalities the past three years were water-related (excluding Hurricane Maria in Puerto Rico).
• Only 4% of water-related deaths were spawned by storm surge. Inland flooding accounted for the other 96%.
• More than half of those water-related deaths were vehicle-related.
Just the past two years, Hurricanes Harvey, Florence and Lane shattered state rainfall records in Texas (61 inches), North Carolina (36 inches), South Carolina (24 inches) and Hawaii (52 inches).
"Twenty-two people lost their lives in Hurricane Florence. Seventeen of those were related to water – and 16 were in vehicles," Graham said.
NOAA’s Geophysical Fluid Dynamics Laboratory reports that tropical cyclone rainfall rates will likely increase in the future because of human-caused global warming. Computer models show rainfall rate increases of 10% to 15% within about 60 miles of a storm in a scenario where global temperatures increase 2 degrees.
If a record-breaking-rainfall storm makes landfall at a key Sunshine State city, Beaman said the worst flooding could occur elsewhere. He pointed out Harvey made landfall near Corpus Christi – but the flooding epicenter was roughly 100 miles to the northeast, near Houston.
What's more, he said the Saffir-Simpson Hurricane Wind Scale has no bearing on flooding potential. Florence weakened from a Category 4 major hurricane to a weaker Category 1 storm before saturating the Carolinas.
Florida factors that determine localized flood levels include topography, the speed the hurricane is moving, rate of rainfall per hour, high tides, and whether the soil is already saturated.
Dan Noah is NWS warning coordination meteorologist in the Tampa Bay area. He said computer modeling shows a rainfall of 13 inches within 12 hours could push the Alafia River near Tampa to the 31-foot level if the soil was already saturated. That's 12 feet above the "major flood stage."
"That’s 10 extra feet of water inside a home that was flooded at 21 feet. Water is heavy. Moving water is dangerous," Noah said.
Despite technological advances, forecasters are many years away from developing a “total water” river forecast, said Al Sandrik, NWS warning coordination meteorologist in Jacksonville.
Sandrik also said Florida's relentless residential and commercial development is a major flooding factor.
"When a lot of people start moving in, you start changing those terrain features. Where you remember it flooded the last time, 15 years ago, well now maybe there's a new shopping center that's gone up. And now, you've got more impervious ground around that area for a parking lot," Sandrik said.
"Then you have a retention pond in there – but retention ponds are only meant to collect so much water," he said.
Follow Rick Neale on Twitter: @RickNeale1
This article originally appeared on Florida Today: 'Water is what's killing people': Hurricanes could cause catastrophic flooding in Florida
