Modeling potential impacts of a breach for a high hazard dam, Elizabethtown, Kentucky, USA

• A hypothetical dam breach analysis of an earthen dam is undertaken.
• Peak breach discharge generated at 1034 m3/sec.
• Maximum flood depths of 2.4 m were estimated.
• Total inundated area impacted 388 buildings and 1725 people.

The USA contains over 87,000 dams of which 17% are classified as being of high hazard potential. Many of these high hazard dams do not have an Emergency Action Plan (EAP) in place, a key part of which includes an inundation map to identify the downstream areas impacted by a potential dam breach. The objective of this study was to conduct a hypothetical dam breach analysis for such a high hazard dam located in Elizabethtown, Kentucky. A hypothetical dam breach was modeled using the Simplified Dam Break model (SMPDBK) that incorporates actual dam measurements and hypothetical breach information based on previous studies of similar dams. Post-processing in ArcGIS produced an inundation map in which flood impacted areas were delineated based on the progression of the peak flood discharge over time. Results indicated that a peak breach discharge of 1034 m3/sec would reach the city limits 2.87 h after the initial breach impacting 388 structures and 1725 people. Key evacuation points and locations of greatest vulnerability were identified based on flood arrival timing and access to evacuation points. This research demonstrates how a combination of dam breach modeling procedures and GIS post-processing can produce an accurate peak outflow breach and subsequent flood inundation map, both key features of an Emergency Action Plan.