Remember all the second-guessing of the Corps of Engineers' actions during the 2009 floods? Lots of people were complaining about how the Corps kept releasing water during the floods, possibly worsening the floods downstream? We covered those complaints thoroughly and so its only fair to tell the other side when it comes out:

An investigation in Vinings has exonerated the Corps at Buford Dam and put the blame on Georgia Power. Apparently the problem was with Georgia Power’s Morgan Falls dam:

“It had rained constantly for 10 days. Then, out of nowhere, there’s this 22-foot spike. It hit us as though it were a tidal wave. It wasn’t a minor surge. It spiked 22 to 29 feet depending on how far down the basin you were.”

“That’s a function of somebody opening a dam,” he said.

.... Flooded neighbors first blamed the Buford dam at Lake Lanier.

Corps of Engineers data show that Buford reduced its releases to the Chattahoochee on Sept. 20. But it never cut them entirely, even as the river buried highways in metro Atlanta and despite the fact that Lake Lanier was not yet full.

Corps spokesman Patrick Robbins, in Mobile, Ala., said the dam released only enough water to produce the electricity needed to run the dam itself.

He said the Corps never cuts flow entirely, because it needs to protect water quality between the dam and the next feeder creek downstream.

Corps data also show that Buford Dam held back enormous amounts of water during the flood and that its releases were small, compared to the volume of water that eventually poured into metro Atlanta.

That’s what turned attention to Georgia Power’s Morgan Falls.

Morgan Falls sits just southwest of Roswell, several miles upstream from Vinings. Built more than a century ago to produce power, the dam began playing a role in regulating the river more than 30 years ago, after Buford Dam was built in 1958.

Buford’s releases cause huge fluctuations in water flow.

Morgan Falls smooths out the surges, holding back and then releasing the water coming downstream to create a steady flow past Atlanta’s Peachtree Creek.

That flow dilutes treated sewage from Atlanta.

September’s rains far exceeded Morgan Falls’ capacity to control the river, Georgia Power says.

The fiercest rain from September’s storms hit metro Atlanta late on Sunday the 20th and early Monday the 21st.

United State Geological Survey stream gauge data show the river’s flow picking up volume steadily as it headed south, then jumping sharply at Vinings like the end of a snapped bedsheet.

Between shortly after midnight on Sept. 21 and 7 p.m. that night, the flow coming into Morgan Falls grew from 5,000 cubic feet per second to 31,000 cubic feet per second. Georgia Power opened eight spillways between 6:30 a.m. and 5:30 p.m. that day.

“Some of the operators who’ve been here a long time say they never remember that many gates open,” said company senior engineer Fred Cox.

The flow at Vinings climbed in tandem with the opened gates.

It quadrupled, from 5,000 to 20,000 cubic feet per second that morning, then doubled again between noon and 9 p.m. that night, at 41,000 cubic feet per second.