Крушение плотины Келли Барнс: трагедия Токоа-Фолс

Kelly Barnes Dam was an earthen embankment dam on Toccoa Creek in Stephens County, Georgia, United States, just outside the city of Toccoa. Heavy rainfall caused it to collapse on November 6, 1977, and the resulting flood killed 39 people and caused $2.8 million in damage. The dam was never rebuilt. A memorial to the dead stands downstream, by Toccoa Falls on the campus of Toccoa Falls College.

In 1899, a rock crib dam was built by E. P. Simpson on Toccoa Creek to create a reservoir for a small hydroelectric power plant that began operating that same year. The plant, now a historical site on the Toccoa Falls College campus called the Old Toccoa Falls Power Plant, produced 200 kW for the town of Toccoa, Georgia. The power plant was transferred in 1933 to the Toccoa Falls Institute, which decided to develop a more stable electric power source and built an earthen embankment dam over the original rock crib dam between 1939 and 1940. After World War II, the dam was again raised, creating Barnes Lake, a reservoir. The modifications provided power for Toccoa Falls Institute until 1957, when the power production was stopped, and the lake was thereafter used only for recreation.

The dam was modified several times, ultimately measuring 38 feet (12 m) high, 400 feet (122 m) long and 20 feet (6 m) wide at its crest. The dam had two uncontrolled earthen spillways. The main spillway was 380 feet (116 m) long, wide and located on the left side of the structure. A low point on the right side and away from the dam could also be used as a secondary spillway when the reservoir levels became too high. The embankment dam was located about 2000 feet (610 m) upstream from the Toccoa Falls and mostly consisted of residual soils and silt. The dam sat on a foundation of silt and stable biotite gneiss (rock). Within the dam embankment were two masonry structures. One helped support a pipe that was used as a low level spillway. The other contained a penstock (pipe) for the hydroelectricity power plant. Neither was being used at the time of the flood.

On November 6, 1977, at 1:30 am, the Kelly Barnes Dam failed after four days of heavy rain: had fallen from November 2 to 5—half of that between 6 pm and midnight on November 5. The rain swelled Barnes Lake, which normally held of water, to an estimated of water. A total of 200 feet (61 m) of the dam failed, causing a peak of maximum discharge to burst downstream. The flood killed 39 people The cost of the damage was $2.8 million. After the flood, Georgia's Governor George Busbee called for an immediate investigation, which was carried out by a Federal Investigative Board of the United States Geological Survey. Their report was released December 21, 1977, with no specific causes cited for the failure. The investigators had no engineering plans for the dam and records of construction on the dam were based on witnesses, pictures, and newspaper articles. The investigation did, however, cite several possible or probable causes. The failure of the dam's slope may have contributed to weakness in the structure, particularly in the heavy rain. A collapse of the low level spillway could have also exacerbated this problem. A 1973 photo showed a 12 feet (4 m), 30 feet (9 m) slide had occurred on the downstream face of the dam, which may have also contributed or foreshadowed the dam failure. Overall, the dam itself was in poor condition and lacked a sufficient design.