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Overtopping performance of earthen dams during record flooding in Columbia, South Carolina




Crookston, B., author
Hepler, T. E., author
Colorado State University. Department of Engineering, publisher

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South Carolina experienced what has been described as a 1,000-year flood on October 4 and 5, 2015. Widespread rainfall from Hurricane Joaquin pounded the state's capital city, Columbia, with over 20 inches of rain recorded in many locations. As a result, over 70 miles of Interstate 95 had to be closed, in addition to local roads and bridges, and thousands of residents had to flee their homes. State-wide, 36 dams failed – 31 state-regulated, 1 federally-regulated (on Fort Jackson), and 4 unregulated. The South Carolina Department of Health and Environmental Control (DHEC) issued emergency orders on 75 additional dams in the state, with the vast majority of them privately-owned earthen dams. Sadly, there were 19 flood-related deaths, including a first responder whose work truck was swept away by the flood. Millions of dollars in property damages were incurred. This paper summarizes the historic storm and associated flooding of October 2015 in South Carolina, including the 74.5 mi2 Gills Creek Watershed in Richland County where 16 inches of rain was recorded in just 6 hours. It documents the overtopping performance of a number of earthen dams, including the overtopping failure and planned restoration of Gibson Pond Dam, as well as the satisfactory performance of Forest Lake Dam that had fabric-formed concrete overtopping protection on its crest and downstream slope. It is anticipated that the information presented in this paper would be of benefit and interest to those involved in dam safety.


Presented at the Protections 2016: 2nd international seminar on dam protection against overtopping: concrete dams, embankment dams, levees, tailings dams held on 7th-9th September, 2016, at Colorado State University in Fort Collins, Colorado, USA. The increasing demand for dam and levee safety and flood protection has motivated new research and advancements and a greater need for cost-effective measures in overtopping protection as a solution for overtopping concerns at levees and dams. This seminar will bring together leading experts from practice, research, development, and implementation for two days of knowledge exchange followed by a technical tour of the Colorado State University Hydraulic Laboratory with overtopping flume and wave simulator. This seminar will focus on: Critical issues related to levees and dams; New developments and advanced tools; Overtopping protection systems; System design and performance; Applications and innovative solutions; Case histories of overtopping events; Physical modeling techniques and recent studies; and Numerical modeling methods.
Includes bibliographical references.

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