Dam Failure Case Study: Canyon Lake Dam (South Dakota, 1972)

DamFailures.Org is an ASDSO project that provides individual dam failure case studies and lessons learned as a resource for dam safety engineers, dam operators, owners, regulators, managers, academia and students to help prevent future incidents.

The Friday afternoon of June 9, 1972 was the beginning of a tragedy for Rapid City, South Dakota along the eastern slopes of the Black Hills mountain range. Scattered showers from the previous days had left the ground saturated while a low-level air mass flowing from the east forced moist air up the 7,000 foot-high mountain slopes. Typically, a fast moving air stream quickly pushes such moisture through the area, but on that Friday afternoon there was a slow, almost-stagnant air mass moving over the isolated mountain range. Rapid City (1972 population of approximately 43,000) didn’t anticipate either the magnitude of the storm or the breach of Canyon Lake Dam.