"The tenth anniversary of the Taum Sauk dam failure serves as a reminder of the very real need for constant vigilance in dam safety," says Lori Spragens, Executive Director of the Association of State Dam Safety Officials (ASDSO) in the US.

In the early morning hours of 14 December 2005, the Taum Sauk upper reservoir dam failed, sending a destructive wall of water through Johnson’s Shut-Ins State Park, one of Missouri’s most popular recreational areas. Fortunately no one was killed by the torrent.

Situated on top of Proffit Mountain in southeast Missouri, the Taum Sauk upper reservoir was one of two reservoirs comprising a pumped storage facility owned and operated by Ameren Missouri. The upper dam failed when instrumentation that regulated water flow into the upper reservoir malfunctioned, causing excess water to be pumped into the reservoir until it overtopped.

As the 0.22km2 reservoir washed over the dam, a 207m wide section of the earthen embankment failed suddenly, releasing a 12-15m high wall of water down the mountainside, stripping vegetation and soil down to the bedrock. The floodwaters inundated State Highway N, pushed vehicles from the road, ripped apart the occupied home of the state park superintendent, and covered the empty state park campground with up to 12m of water. The combination of water and sediment caused significant property and environmental damages to the park and limited recreational uses of the Black River for months.

“This dam failure is a prime example of a disaster that could have been much worse. Had it not occurred in the winter, dozens of campers would likely have been killed; likewise, had it not occurred in the early morning hours, additional vehicles would likely have been on the highway that flooded," said Spragens.

While the people caught in the flood have recovered from their injuries, Johnson’s Shut-Ins State Park suffered permanent environmental damages. In a settlement reached nearly two years after the failure, the dam owner agreed to pay US$177.35M to the State of Missouri for loss of tourism revenues and damages to park lands and natural resources.

Ameren incurred additional expenses rebuilding the dam, which now incorporates multiple redundant systems to ensure that a repeat of the overtopping event never occurs.

“Dam maintenance and upgrades cost a lot," said Spragens, "but they are much less expensive than clean up, repairs, and restitution following a dam failure."