10 years later: Experts say devastating floods could happen again

FILE: Clarkdale Elementary School floods

ATLANTA — Flooding experts believe the devastating floods that hit metro Atlanta in 2009 could happen again.

Kent Frantz, service hydrologist for the NWS, told Severe Weather Team 2 meteorologist Katie Walls that after living through that experience, he doesn't discount anything.

In a 24-hour period on Sept, 20-21, 2009, more than ten inches of rain fell in parts of Douglas, Paulding, Cobb, Carroll and Gwinnett Counties.  The greatest amount was 21 inches near Douglasville.  The ground was already saturated with five to seven inches of rain that had fallen earlier that week.

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"I do think extreme events will continue to happen and could happen again in the same locations," Frantz said.

The flooding caused numerous gauges to fail, including one at Sweetwater Creek.  The National Weather Service has since installed new high water staff gauges.

Frantz said the chances of getting 10 inches of rain in one day is one in 10,000. Still, daily thunderstorms in North Georgia can produce up to three inches on any given afternoon.  Even that small amount can cause flash flooding.

"On a routine basis, a lot of the flash flooding we do have is because of the rapid runoff from poor drainage areas of streets, or areas that are not natural anymore.  They've been altered in some way," Frantz said.

Dr. Brian Stone is a professor of City and Regional Planning at Georgia Tech.  He said Metro Atlanta has been one of the most rapidly growing metropolitan areas for the last 20 years.

Growth is good, but not for the area's trees or urban flooding.  Stone told Channel 2 Action News there's a direct connection between the lack of trees and increased storm water runoff.  He says it's because the trees soak up the water.

"Independent of increasing the amount of concrete and asphalt, just losing those trees reduces the ability to absorb that rainfall," said Stone.

"We don't always need to fully clear-cut a sight when we develop it," Stone said. "It can cost a little more up front, but it costs a lot less over time to deal with the various runoff issues."