DAM BREACHES INITIATED BY THE OCTOBER 2015 RAIN EVENT

The October 2015 rainfall event in South Carolina became the second largest disaster in South Carolina since hurricane Hugo in 1989. South Carolina residents were faced with washed out bridges, roads, failed dams, flooded neighborhoods and catastrophic economic losses. Due to the storm the state of SC will remain focused on long term recovery issues for the next few years. One of the major problems that the state encountered was the failure of many of the dams across the region as the record rainfalls resulted in river flooding and overtopping and undermining many dams. As the state of South Carolina started to inspect and classify dam failure, it was discovered that the state lists of dams did not correlate with the federal lists. The identification of redundant dams between the original DHEC and NID dam lists provided valuable information to state and local agencies that are responsible for inspecting, maintaining and managing dams throughout the state. The ability to determine which dams were redundant between the lists could save these agencies the time, resources and money associated with dam inspection across the state.

Students at the College of Charleston, were able to verify and validate the lists of dams for the state agencies to help create a single list of all unique dams in the State. An initial list of 4,780 dam points across the State was culled to a more manageable 2,506 dams. As of December 1, 2015 the state of South Carolina has assessed all 652 Class 1 and Class 2 dams and have issued emergency orders covering 76 dams and identified 167 additional dams as being damaged and in need of repairs or requiring maintenance.

The study provides case study information highlighting why dams failed during the record-breaking October 2015 flooding event. Information on influences to dam infrastructure, such as land use type above and below the dam, surrounding watersheds, and underlying soils, highlight patterns associated with higher hazard dams. This analysis is crucial for developing effective dam management and maintenance practices, as well as educating South Carolina locals about dam safety and their exposure to risk during high flooding events.