Houston evokes memories of 2009 Atlanta flood. Could it happen again?

7:03 p.m Wednesday, Aug. 30, 2017 Local
Earl Knight uses a shovel as an oar as rows down the still flooded Oglesby Road in Powder Springs with Cornell Daniels in September 2009. Bob Andres, bandres@ajc.com

Years later, a heavy rain triggers a flutter of panic inside Julie England, owner of Ty-Bolts in Austell.

Prolonged rainfall in 2009 caused massive flooding that damaged 20,000 homes and businesses — including her hardware supply store — and killed 10 people throughout metro Atlanta.

England knows it would take far more than an afternoon rainstorm to cause flooding on the scale that devastated her family business eight years ago, or Houston today. Still, the rain makes her nervous.

“It’s only by the grace of God that we’re still here,” England said. “I really feel for those people in Texas.”

Atlanta may be far from the coast, but like Houston, it is a sprawling city and its geography makes it uniquely vulnerable in other ways.

“The Southeast is the only place, frankly in the United States, that gets every type of storm or extreme weather event you could think of, from hurricanes to tornadoes to floods,” said Marshall Shepherd, the director of Atmospheric Studies at the University of Georgia. “That’s why it’s even more imperative for us to be completely prepared.”

Shepherd said studies clearly show that the heaviest rains that occur in a given year are on average heavier than they were in years past, and many cities haven’t caught up.

Today, with construction booming and weather extremes expected to get worse, experts say local governments need to take steps to mitigate flood risk.

“Engineers assume that the rainstorms of 2017 would look like the rainstorms of 1970, and that’s just not the case,” Shepherd said. “We certainly have to be prepared and develop an infrastructure that can withstand what I call 21st century rainstorms.”

Numerous factors contribute to flooding, including heavy rainfall, impervious surfaces like paved streets and buildings, poor drainage and construction in flood zones.

Flood risk in Georgia is determined jointly by the Federal Emergency Management Agency, or FEMA, and the Georgia Department of Natural Resources. Areas of risk included in the “flood insurance rate map” are commonly referred to as floodplain. Local governments are responsible for enforcing building codes in those areas, or buying up land to prevent it from being developed.

But just because a home or business is located outside the floodplain, doesn’t mean it isn’t at risk. In fact, according to FEMA, nearly a quarter of all flood insurance claims are from outside areas considered to be at a high risk of flooding. The agency encourages everyone to have flood insurance.

Engineer Brian Bledsoe heads UGA’s Institute for Resilient Infrastructure Systems. He said better communication is needed to correct widespread public misconceptions about flooding. For example, he said, many people don’t realize that a “100-year flood” has a more than one-in-four chance of occurring in a 30-year mortgage. A 500-year flood has a 15 percent chance of happening in a human lifetime.

“We have this false notion that these are extremely rare events when they’re actually more common than we want to believe,” Bledsoe said. “Rainfall is getting more intense and land use is changing — there’s more urbanization — so all those variables interact to affect flood risk.”

Flood maps have been updated across the metro region in recent years. DeKalb County has bought several properties where there has been repeat flooding and turned them into greenspace. Gwinnett County improved its standing with the National Flood Insurance Program.

Cobb County was among those worst hit by flooding in 2009. Since then, Cobb has purchased 77 homes in flood hazard areas and more than 125 acres of vacant floodplain. It constructed two storm water detention facilities – one on Mark Avenue and one at Chastain Meadows, both on the Noonday Creek watershed.

Some wonder if the county is doing enough, pointing to Houston as a warning against poor planning and overdevelopment. Experts say urban sprawl and lack of zoning have exacerbated the disaster in Texas.

West Cobb resident Keli Gambrill of People Looking After Neighborhoods said she was inspired to get involved in local government when construction next door caused her property to flood.

“As soon as they started disturbing the land and manufacturing the terrain, my backyard turned into a lake,” she said.

Gambrill said denser housing developments are replacing multi-acre single family homes, and questioned whether the retention ponds built to off-set them are working.

The city of Atlanta was not as severely affected by the 2009 floods, but faces many challenges when it comes to managing stormwater. Like many cities, it contains older neighborhoods and buildings constructed on creeks and watersheds. In parts of the city, a combined sewer system moves sewage and stormwater together. This type of system, which is no longer built, can overflow and cause flooding and contamination.

More than half of the stormwater infrastructure within Atlanta is on private property not maintained by the city.

Lately, Atlanta has started looking toward a comprehensive approach to flooding and other threats with the official formation of its Office of Resilience last month. Atlanta was recently selected for funding and support as one of “100 Resilient Cities,” a program pioneered by the Rockefeller Foundation. Resilience refers to a city’s ability to respond to short-term shocks (disasters like floods) and long-term stresses (traffic and housing).

City officials point to “green infrastructure,” like the Old Fourth Ward Park where the pond doubles as stormwater retention, and four miles of permeable roadways. This year, the city passed a floodplain management ordinance prohibiting construction in the 100-year floodplain.

“We have the dichotomy of drought and flooding, so that presents a particular set of challenges,” said Stephanie Stuckey, Atlanta’s chief resilience officer. “We have to deal with how we increase our water capacity in times of water shortage, which we’re doing through Bellwood Quarry, but at the same time having that excess capacity in times of heavy rainfall and flooding.”

Stuckey said her office is preparing to present a “resilience plan” for the city of Atlanta, including a stormwater action plan, on October 17.

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