In Florida, the rain stopped, but the flooding hasn’t. Why?

By Neelam Bohra

Days after the rain from Hurricane Ian stopped falling in Florida, flooding continued to threaten communities across the state on Sunday, from coastal areas like Daytona Beach to inland cities like St. Cloud.

The lingering danger was a result of a phenomenon called compound flooding: floods from storm surge block rivers, which are already cresting from heavy rainfall, from draining back into the ocean.

This can sometimes even create a temporary reversal in a river’s direction, bringing more water inland to communities that already have too much of it.

“It’s kind of like if you’re trying to drain a bathtub, but water is coming up through the drain, exacerbating the flooding,” said Felix Santiago-Collazo, an assistant professor at the University of Georgia who researches storm flooding.

As a result, some residents are finding their roads flooded days after thinking the worst was over. Mr. Santiago-Collazo said compound flooding has occurred more frequently over the years as hurricanes become stronger because of warmer ocean waters.

Water also takes time to move downstream. As it drains toward the ocean, flooding can occur along coastal areas as estuaries, where rivers meet the ocean, rise.

Maitane Olabarrieta, a coastal engineering researcher at the University of Florida, said the public should be better educated on the potential for compound flooding so communities that aren’t on known flood plains can prepare themselves during extreme weather events. But that does not mean there is an easy solution.

“It’s not clear to me how this could be prevented,” she said.

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