Geotechnical Observations of Dams Failed During the 2015 Historic Flooding in South Carolina

This paper presents a description of post-flood reconnaissance and geotechnical investigation of four earthen dams that were breached or damaged following an extreme flooding event in South Carolina in 2015. As a result of unprecedented rainfall and flooding that occurred during a five-day period at the beginning of October in 2015, a total of 51 earthen dams failed and nearly 200 were damaged. Many of these dams failed due to overtopping that led to a breach of the dam. Among the four dams investigated, full breach was observed at three dams; two of which were overtopped, and one was not. The fourth dam was not breached but was severely damaged. For each of these dams, the paper documents background information, pre-flood conditions, post-flood field observations and measurements, and laboratory testing results of collected soil samples. Impacts of vegetation on the dams and the effects of dam failure on critical infrastructure are also presented. The detailed descriptions and geotechnical investigations of the dam failures presented herein serve as case histories that can be used for dam breach modeling and risk assessment of dam failure.