Austell faces rising danger at juncture of 5 creeks

Austell faces rising danger at juncture of 5 creeks

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090922 Atlanta: Some homes in this subdivision in Cobb County near Austell were high and dry, but gave their owners no way to get past the flood waters September 22, 2009 . Brant Sanderlin, bsanderlin@ajc.com

When the floodwaters finally receded in Austell, city leaders, the federal government and a giant rail yard in the crook of two creeks all took the heat from angry victims.

The small city's mayor had answers.

"We had 20 inches of rain, and there's nothing you can do about it," said Mayor Joe Jerkins, adding that government had done all it could and the rail yard "had absolutely nothing to do with the rain that we had."

The words will sound familiar to Austell residents who squeezed into civic meetings last fall, seeking an explanation for September's epic floods.

But they were spoken more than four years ago. Austell's creeks have made a mockery of flood prevention policy for decades.

One of September's hardest-hit cities, Austell sits at the juncture of five creeks and in the bull's-eye of a suburban building boom. Rainwater that once soaked into fields or forests now washes off parking lots and roofs, then heads — it seems — to Austell.

An Atlanta Journal-Constitution analysis published Feb. 21 found a dramatic link between the increase in man-made, nonabsorbent, "impervious" surfaces in the metro region and the size and speed of floods. Regional shortcomings in storm water planning aggravated the problem, the AJC found. Those flaws included splintered, jurisdiction-by-jurisdiction planning that ignored downstream impact and federal flood maps that didn't keep up with that development.

Austell, with 6,300 residents, plans for flood prevention as well as, or better than, most communities in the region.

But it suffers from the region's shortcomings, too. Combined with its natural vulnerability to floods, those flaws have made Austell the New Orleans of the region, said attorney Don Stack, who has represented hundreds of homeowners with development-related flooding problems.

"You've got the natural features of the river, a rail yard that changed the hydrology, development that shouldn't have been developed."

The region's piecemeal flood planning, for instance, gives Austell no say in upstream development.

The already flood-prone city sits on the low end of a suburban drainage basin where the kind of hard surfaces that make creeks rise higher and faster increased by more than 50 percent over a decade, the AJC found.

Inside Austell's borders, the city also allowed, or was forced to accept, development that appeared to defy common sense.

Private property rights and litigation, or the threat of it, helped put development in areas that conventional wisdom said would flood.

The 8-year-old, 450-acre Norfolk Southern Intermodal rail yard is one example, with its acres of pavement nestled in the flood-friendly juncture of the Powder Springs and Sweetwater creeks.

Another is Mulberry Creek, a 2003 subdivision downstream from the intermodal.

 

Problem known since 1964

Austell's tendency to flood has been recognized since at least 1964, the first year the city asked the U.S. Army Corps of Engineers for help.

Between 1964 and 1995, the corps studied Austell four times. Its conclusion: The city is built in a bad place.

Austell has been described as the catch basin for Paulding, Cobb and Cherokee counties.

The biggest of its five creeks, the Sweetwater, flows in from Paulding, one of the nation's fastest-growing counties.

The other four creeks bunch into the Sweetwater from the north just as it flattens out and winds through Austell. In a big rain, water can get into Austell but it can't get out.

The corps' studies offered four potential solutions, but deemed none worth the cost. Even the cheapest — dredging and cleaning out the creek — failed the dollar-to-dollar cost-benefit test then needed to get federal help, said corps spokesman Patrick Robbins.

 

1990 back-to-back floods

The final corps studies followed two back-to-back floods in 1990, both of a size hydrology experts consider rare.

A 100-year flood is so big that hydrologists give it one chance in 100 of happening any given year. It's the benchmark for national flood policy.

The Sweetwater almost reached the 100-year mark in February 1990, then hit it the next month, said Mayor Jerkins, who called in the corps in response. "I have lived here all my life, and in 1990 was the highest I have ever seen the water rise," he would tell residents 15 years later, after an even bigger flood.

That was in 2005, when the Sweetwater rose "3 foot and 2 inches higher than in 1990," Jerkins said. He called it a 500-year flood, although the U.S. Geological Survey says it didn't quite hit that. The 500-year flood has a 0.2 percent annual chance.

While Jerkins blamed rain, other city officials wondered.

"The 500-year floods have caught us all by surprise," city Councilwoman Beverly Boyd said. "It could be growth. But it's not just ours. If it was just ours, we wouldn't have much of a problem because we haven't grown that much."

Four years later, the Sweetwater outdid itself again. The USGS couldn't rate September's flood, except to say it was much bigger than a 500-year event.

 

Building boom upstream

A lot changed in the Sweetwater's drainage basin during the years when its floods got worse.

Since the last corps study, areas upstream of Austell issued 175,000 new home permits, according to a federal database.

Homes and the roads, driveways and shopping centers that serve them mean more rain-repelling surfaces on ground that once soaked up rain.

Planners required drainage systems, but only recently began taking cumulative downstream effects into account.

In some creek basins, such as Powder Springs Creek upstream of Austell, man-made surface area grew by 50 percent or more in the past decade. Streams through such areas are "flashier" — peaking faster and higher after rains — than in the past, the AJC analysis shows.

The analysis found a tipping point: Once hard surfaces cover 30 percent of a creek basin, each addition of pavement has an increasingly bigger impact on streams.

Austell sits in the pincers of two problematic creek basins. In addition to the jump in hard surfaces in the Powder Springs Creek area, the Olley Creek basin has passed the 30 percent tipping point.

As development continued upstream, Austell grew, too — although modestly. The city issued 1,050 residential building permits between the corps studies in 1995 and 2008, the federal database said.

Austell also added developments — like the Norfolk Southern Intermodal in 2001 and Mulberry Creek subdivision in 2003 — in areas residents said would flood.

 

Outcries unheeded

The intermodal is where the railroad transfers cargo containers between trains and trucks.

Austell, Powder Springs, Lithia Springs, East Point, Cobb County, the Cobb Chamber of Commerce, the Atlanta Regional Commission, the state Senate and, for a time, the U.S. Environmental Protection Agency all tried to stop it.

The railroad prevailed. Its federal lawsuit against Austell brought a landmark decision exempting such facilities from local zoning.

The 450-acre intermodal stretches southeast along Powder Springs Creek to its juncture with the Sweetwater. The area had flooded before, as a local environmentalist wrote the corps in 1997.

"Someone, somewhere, in the halls of officialdom at the railroad mistakenly thinks that trucks and trains are capable of floating," wrote the late Pamela Blockey-O'Brien. The facility is "at the lower end of the 245 square mile drainage basin of Sweetwater Creek and the area floods."

"Massively."

The railroad built four huge ponds and new wetlands to control runoff. The system exceeded local and state standards, didn't change the 100-year flood plain and let water into creeks more slowly than undeveloped land, company studies said.

The state-of-the-art-plus system is typical of Norfolk Southern projects, said spokeswoman Susan Terpay.

But Stack, the lawyer, said the intermodal likely changed creek behavior in ways public policy doesn't grasp. Storm water policy addresses the rate of runoff, but not total volume.

The intermodal increased total runoff and that matters, he said: "If I'm going down the highway at 80 miles per hour, it makes a difference whether I do that for two minutes or two hours, in terms of how much ground I cover."

The intermodal also meant that "water that used to move in sheets, in a widespread area, ended up being focused into four discharge points. What should have been spreading out was concentrated," he said.

No one knows what the intermodal or building upstream did to the Sweetwater. A comprehensive study hasn't been done in years. City public works director Randy Bowen said a new one is needed. "We are actively trying to get a restudy of Sweetwater Creek," he said.

The Cobb County Commission agreed last week to do that study.

 

Extreme, yet typifying

Austell's situation may be extreme, but it exemplifies problems that face storm water planners across the region.

Development has outpaced the tools, such as flood maps, used to measure the impact of lots of rain. Local control means communities can't affect or even understand what upstream building does to their creeks.

And property owners have rights.

That's what led to Austell's 2002 approval of the Mulberry Creek subdivision, which sits on an old horse farm partially inside Sweetwater Creek's 100-year flood plain line.

Neighbors and city officials warned of flooding. Councilman and subdivision opponent Bo Traylor said water had been as high as a man's head there: "It was common knowledge that the area floods," he said last fall.

City officials say they OK'd the 25-house subdivision because they believed the property owner could sue and win. "If they met our development standards, then they have a right to develop," said Community Service Director Jim Graham.

Development laws try to balance public safety and private property rights. Austell does that by allowing building in the 100-year flood plain only if lots are raised up out of it. The lowest floor must be 3 feet above the line.

It's a common standard, although not endorsed by everyone, since built-up flood plain moves water elsewhere. Douglas County bans building in the flood plain. The region's water district encourages other options, too.

The standard requires reliable flood plain data, which is in short supply.

Even the newest Federal Emergency Management Agency flood risk maps, released in December 2008, are based partly on Sweetwater Creek hydrology studies that are 24 years old.

Mulberry Creek flooded in 2005 and again last fall, when 19 of 25 houses were damaged.

Both floods far exceeded the official 100-year mark.

 

A train wreck

The Sept. 21 flood was a hydrological train wreck for Austell.

According to USGS, 18 inches to 22 inches of rain fell on Paulding, west Cobb and Douglas counties Sept. 18 to Sept. 22. The soaked ground repelled rain into creeks almost like pavement.

A Norfolk Southern gauge recorded 9 inches in four days. A monitor just upstream saw 11 inches in 24 hours. Typical Atlanta rainfall is 50 inches in a year.

Flooding near the intermodal was dramatic. At an intersection near its tip, water reached a stoplight. Workers at a neighboring recycled paper company, Caraustar Industries, saw water on intermodal tracks rise to an overhead bridge.

The water swamped Caraustar from an unusual direction, Chief Financial Officer Ron Domanico said. The Sweetwater skipped a bend and charged across Caraustar's property instead, pushing over a power pole, hurling 17 tractor trailers into a park and jamming another five under a bridge.

The water, it seemed, "was coming from the intermodal," Domanico said.

Data from Norfolk Southern's monitors, obtained under the state Open Records Act, tell a more confusing story.

As the rain fell, the intermodal's four detention ponds slowed the rain's path to the creeks as designed. They nevertheless sent lots of water — 2.9 million cubic feet on Saturday and 9.3 million cubic feet on Sunday — into the creek the weekend before the flood.

The Sweetwater's flow past the rail yard on a dry day last fall was about 71 cubic feet per second — or 6.2 million cubic feet a day.

On the Monday of the flood, the creek's flow was 9,785 cubic feet per second, which translates to a daily flow of 800 million cubic feet. As Jerkins later put it, the intermodal "wouldn't even have raised the water to the thickness of paper. The problem here was the rain."

But, what the rail yard added to the creek that day is a mystery. Two monitors were underwater and reporting nothing. Two others reported releases of 6 million cubic feet, although Norfolk Southern says it cut power to them that day: The reading may not be complete. By 1 p.m. that day, the creek was so high that it flowed backward into a rail yard retention pond.

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