Dam Failure Case Studies from the 2015 South Carolina Flood

In October 2015 South Carolina experienced historic rainfall and flooding leading to dam failures statewide. The rainfall was estimated to be more severe than the 1/1000 annual exceedance probability storm in parts of the state and led to flooding that caused widespread damage. Following the flooding and resulting dam failures, dam safety officials in South Carolina issued emergency orders to dam owners, responded to dam failures, and inspected hundreds of dams statewide. Additionally, the state dam safety officials evaluated dams for hazard reclassification and supported dam safety recovery efforts. 

This paper will focus on a select number of dam failure case studies to illustrate the story of the 2015 South Carolina Flood, including its impact on the performance of many dams throughout the state and the rehabilitation efforts for affected structures. 

● Lexington Old Mill Pond Dam, Gibsons Pond Dam, and Barr Lake Dam: These three dams are located in series in the Twelve Mile Creek watershed. Dam safety concerns were noted in inspection reports, particularly for the Lexington Old Mill Pond Dam prior to the 2015 flood. Following their failures, all three dams have been rehabilitated. 

● Cary’s Lake Dam: This dam had a unique configuration with two auxiliary spillways, but this failed to provide enough spillway capacity during the flood, causing the dam to fail. The dam was ultimately rehabilitated with a spillway constructed in the breach location reusing elements of the remaining dam and spillways. 

These case studies will spotlight the immediate flood impacts, long-term recovery from the flood, and challenges following a major flood.