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FL - Ian's historic Orlando rain has experts seeking ways to hold back floods

WINTER SPRINGS, Fla. — Lisa Roney was awake in the overnight hours watching the power of Tropical Storm Ian when the water started coming in the back door.

Her husband grabbed a shop vac while Roney, 62, guided rivers of water out the front door with a mop. Two soaked rugs and some soggy drywall later, Roney said they prevented the worst.

“We were desperate,” the retired professor said. “We knew we did not have flood insurance, so we just worked our asses off to save our house.”

Roney admits her backyard gets “swampy” in summer storms, but her house isn’t in a floodplain. She says the water that filled her house didn’t come from the rain; it came from a nearby retention pond that overflowed.

Ian’s record rainfall was rated as a 1,000-year rain event by National Oceanic and Atmospheric Administration standards, easily overwhelming Central Florida’s stormwater infrastructure and causing widespread flooding.

With climate change predicted to bring more such rain events in the future, with both greater frequency and intensity, scientists and engineers are calling for local governments to review their standards and start planning for the wetter world to come.

1,000-year storm

Hurricane Ian was downgraded to a tropical storm while still 40 miles south of Orlando in the early morning hours of Sept. 29. Yet it went on to drop a historic rainfall on Central Florida.

Orlando saw between 12 and 13 inches of rain, with some areas seeing as much as 16 inches, according to the National Weather Service in Melbourne. Winter Springs, where Roney lives, received 14.97 inches, the weather service reported.

In some places such as Lake Wales, where rainfall hit nearly 17 inches, the storm was categorized as a 1,000-year rain event, according to the National Oceanic and Atmospheric Administration.

Jeff Carney, director of the Florida Institute for Built Environment Resilience at UF, says that designation isn’t as impressive as it sounds. “I’ve lived through about three 1,000-year events in my life,” he said. “I’m not that old.”

The designation of storms by year doesn’t mean that these kinds of events only happen once in that many years. It is the likelihood of any storm reaching that strength and effect in any given year. Essentially, there was a 1-in-1,000 chance of Hurricane Ian causing the flooding it did.

Carney says these numbers can be useful for understanding the rarity and severity of storms, but that they don’t reflect an easy, mathematical definition.

“That number is clearly a rough estimate,” he said. “Just the science alone is probably very old.”

Yet these numbers guide the standards for stormwater infrastructure and other preventative measures for flooding.

In Orlando, the storm sewers are built to handle a 10-year storm for six hours, said city spokeswoman Ashley Papagni.

“All development within the City is required to meet the St. Johns River Water Management District stormwater management design criteria,” she said in an email.

In Seminole County, retention ponds such as the one Roney says overflowed into her home have to meet a 25-year, 24-hour design standard, according to the county’s comprehensive plan.

Increasing strength

The problem is the storms are getting stronger.

“Nowadays, a normal storm can probably reach a 25-year, 6-hour standard,” said Ni-Bin Chang, director of the Stormwater Management Academy at the University of Central Florida.

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