Georgia floods ‘epic,' officials say

By Mashaun D. Simon

The Atlanta Journal-Constitution

"Epic" is how officials are describing the floods that hit metro Atlanta earlier this week.

According to the U.S. Geological Survey (USGS), the floods were a "once in 500 years flood," meaning the odds of such a thing happening are less “than 0.2 percent in any given year.”

"It is epic!" said Brian McCallum, assistant director for the USGS Water Science Center in Georgia. “The USGS can reliably say just how bad these floods were.”

They are calling this a 500-year flood because of the likeliness of it occurring is so rare, said McCallum. "We could have another flood next year, or floods back-to-back and still be considered 500-year floods because of the probability."

The data was gathered from their “real-time stream-gauging network,” said the USGS.

Here's some data gathered from the Atlanta area:

* USGS crews measured the greatest flow ever recorded on Sweetwater Creek near Austell as 28,000 cubic feet per second.

* The Yellow River stream gauges in Gwinnett, DeKalb and Rockdale counties measured flows between the 1 percent chance (100-year) and 0.5 percent chance (200-year) flood magnitude.

* Flows caused by the rain at Peachtree Creek in Atlanta were only near the 10 percent chance (10-year) flood magnitude, but the backwater effects from the Chattahoochee River pushed water levels over the 0.2 percent chance (500-year) flood at the gauge location.

* On the Chattahoochee, USGS measured a 1 percent chance (100-year) flood at Vinings and Roswell.

Twenty gauges were damaged during the downpour.

“We expect that all but one gauge should be operational by the end of the day,” said McCallum. “Fixing the gauges is our priority now.”