Inland flooding could be the worst part of Florence

Florence could pose threat days after landfall

NEW ORLEANS (WVUE) - The surge and wind make headlines, but as people flee the coast ahead of Florence, evacuees and officials need to pay close attention to avoid the biggest tropical killer.

The most dangerous part of this storm may not make itself known for days.

Jeff Graschel is a National Ocean Atmospheric Administration hydrologist with the Lower Mississippi River Forecast Center.

“Right now they are calling for 20 to 30 inches of rainfall with upwards of some higher, 40-inch rainfalls.”

Last year, Harvey dropped nearly double that along the Texas and southwest Louisiana coasts, but this is different territory.

“The hills and topography will make the flash flooding even worse,” Graschel said.

Even as Graschel covers the Mississippi River Basin, some of the water from Florence could end up in the Mississippi as a river in western North Carolina actually drains into the Tennessee river that moves into the Ohio. While Graschel doesn’t think it will make a significant impact in the Mississippi, it could be noticed.

He also says the while water ponds in our flat terrain, gravity can multiply the effects of so much water.

“You can imagine 10 or 20 inches of rainfall falling down a mountainside or a hillside," Graschel said. "It’s going to move very quickly down into the areas where you potentially could have cities and homes impacted.”

Ken Graham is the director of the National Hurricane Center.

“We’re getting pretty confident that we are going to have this system slow down,” He said Wednesday morning, emphasizing that he wants to make sure people understand all the risks. “When you slow down like that, the rainfall is going to be, in some cases, record rainfall.”

Graschel hopes North Carolina remembers another "F" storm almost 20 years ago.

“In North Carolina back in 1999, Floyd kind of did the same thing," he said. "We had a pretty significant hurricane system that came in and then dumped copious amount of rainfall.”

The National Guard and Coast Guard pulled people from rooftops in nearly 1,700 rescues. Fresh water flooding caused most of the 51 deaths in North Carolina.

“They’ve had some experience with that and stuff, but certainly if the numbers that they are projecting at 30, 40 inches - that’s even larger than what they had with Floyd,” Graschel said.

High surge will also prevent rivers from draining properly, so even far inland Florence requires alert. It could be two to three days of rain before the river begins to rise, and one of the reasons this type of flooding is so deadly is because it can be well removed - both in distance and time - from the main hurricane landfall.

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