GEOSYSTEM FAILURES FROM A 1000-YR FLOOD EVENT: DAMS

A series of disastrous dam failures caused significant damage to communities throughout South Carolina in October 2015. SC-DHEC reported 32 dams breached, with 19 of them located in Richland and Lexington Counties. Of those, at least 7 of them are classified as high-hazard-potential structures (C1) and 9 are classified as significant-hazard-potential structures (C2). South Carolina has at least 2,500 dams, of which 180 are classified as C1. Across the country, dams that comprise the flood-control infrastructure are aging and in many cases their structural health is deteriorating. Many of these dams are privately owned and often lack the attention and funding needed for maintenance, monitoring and upgrading. Overtopping, foundation defects, erosion, and structural failures are typical causes of dam failures. Earthen dams are not designed for overtopping and these soil structures fail quickly when erosional degradation produces a breach. The failure of dams in South Carolina during the extreme rainfall, which led to the catastrophic flooding of Columbia and surrounding areas, is a highly illustrative example of the consequences of dam failure.  

Results from a post-flood reconnaissance study aimed to collect perishable data from dams that failed during the extreme flooding in Columbia will be presented. The study included collection of extensive photographic evidence and documentation of descriptive information related to the failure; collection of soil samples, and field and laboratory geotechnical tests. These data form valuable sets of well-documented case histories that can be used in the future to support large-scale research for advancing our fundamental understanding of complex failure mechanisms in extreme scenarios.