Kelly Barnes Dam Failure

Toccoa, GeorgiaNovember 6, 1977

Kelly Barnes Dam Failure

• Failed about 1:30 am on November 6, 1977• 39 people were killed• Damages were estimated at $2.8 Million• President Jimmy Carter, at request of Georgia Governor

George Busbee, authorized the Corps of Engineers make technical evaluation of dam and cause of failure

• Assessment team included U.S Army Corps of Engineers, USGS, U.S. Soil Conservation Service, National Weather Service

• Failure was to become the catalyst for the states establishing dam safety programs for private dams

The Site• Dam and lake were located up a

valley about 2000 feet upstream of Toccoa Falls in Toccoa, Georgia

• Valley stream bed was about 40’ wide

• The Falls were about 100 feet high

• Immediately below the Falls was the campus of Toccoa Falls Bible College

• The top of dam was at about elevation 1140 and the campus was about 850 – a difference of almost 300 feet

History of the Dam • A rock crib dam was built about 1899• Used to power a small hydroelectric plant at base of the falls• In 1937 Toccoa Falls Bible Institute built an earth dam over the crib

dam for a more reliable power source• After WWII, earth dam was again raised• Over time additional pipes/penstocks were installed in the dam

and down the valley to the power plant• Served as a power source until 1957• After 1957 the lake continued to be used as a recreation source• The dam remained virtually unchanged until failure and no

evidence was found of any inspection or maintenance program for the dam.

Dam Configuration Just Before Failure

• Dam was about 38 feet high – top elevation about 1140 msl• Dam was about 400 feet long , only about 200 feet of which was

over 20 feet high• Crest width varied but averaged about 20 feet• Normal pool of about 42 acres ( 410 acre feet – 18 million cubic

feet of water)• Full pool was about 630 acre feet ( 27 million cubic feet of water)• An earth spillway beyond the left abutment and a “low spot” in the

reservoir rim on right of dam provided flood control• There was apparently no intake structure for normal pool control• Downstream slopes were steep ( 1v on 1 h in places) and had many

large trees

Conditions Prior to Failure on November 6, 1977

• Between October 25-26 the area experienced about 3 ½ - 4 ½ inches of rainfall

• More rain began on November 2 and by November 5 the area had received about 2 ½ inches of additional rain

• On the evening of November 5-6, there were high winds in the area and one small tornado in the region

• The National Weather Service estimated that the total rainfall between November2 and November 6 was about 7”

Dam Failed at about 1:30 am on November 6, 1977

GA HWY 17 Bridge Mobile home washed away

Impacts of failure

Impacts of Failure

Falls after the failure – note rubble Dorm flooded to second floor

Likely Cross Section

• Dam contained remnants of old construction – crib dam

• Pipes for penstocks embedded in dam – some dating to early 1900’s

• Dam section was homogeneous – no filter zones

• Slopes were irregular• Tree roots penetrated dam

Photos of Failure

Lakebed looking downstream Breach looking Upstream

Plan of Failure

Photos of Failure

Breach Breach looking upstream

Views of Breach

Left side of Breach Right Side of Breach- note remnants of

rubble, crib dam, pipes, root penetration

Photos (cont.)

Spillway in Left Abutment Ride Home

Obvious Deficiencies in Dam That May Have Contributed to Failure

• Mature trees on dam with deep root penetration

• Buried and deteriorating metal pipes in dam• Steep slopes• Lack of any inspection or maintenance

Possible Failure Scenarios

• Slide or slope failure leading to crest breach or “piping”

• Tree blowing over leading to “piping”• “Piping” along one of the abandoned metal

pipes in the dam• Overtopping• Combinations of the above

Results of the Failure• Before failure, Corps personnel in Atlanta lobbied for a state dam

safety law for private dams – legislature did not support. • After failure – Federal government mandated states set up dam

safety laws or the federal government would do so. • Federal Government mandated an inventory of private dams and

provided assistance until states could develop capability and necessary legislation.

• During the late 1970’s and early 1980’s, nearly all states adopted dam safety laws

• Thought there was some minor regulation of dams in Virginia during the 70’s and 80’s , the Virginia Dam Safety Program was made into law in 1989.