CONYERS - It was decided floodplain maps for Rockdale County did not need to be altered following the devastating floods that submerged some residents a couple of weeks ago.
"There's a method to the madness," said Rockdale County flood plain manager Kent Asher.
No changes were needed because recent floods were not beyond a 500-year flood event, which is the most extreme case of flood flow.
Today's maps go to a 100-year floodplain, meaning the chance of a flood is 1 percent in any given year.
Working in the county's Geographical Information Systems division, Asher said they have done a future flood analysis, using a full build-out scenario. A full build-out scenario considers when less water is being absorbed and everything is built on the ground.
"This was a fluke (given) that the entire region was rained on prior to the event," Asher said. "And water follows the rules of physics in that it rolls down hill and we're downhill from where all that water was."
Asher explained maps are based on mathematics, the amount of anticipated water flow and the elevations.
"It was such a combination of things," Asher said. "It may not ever happen again in anyone else's lifetime."
Asher explained the 1994 floods were the last time there were two 100-year events.
"Again it's a probability," Asher said.
The latest Rockdale County flood plain maps were updated in 2001.
"We do not encourage any construction in the flood plain. We discourage it very strongly in the ordinance," Asher said. "We don't allow construction in the flood plain with some very minor exceptions."