Teton Dam collapse. June 5, 1976. “Teton Dam near Rexburg, Idaho suddenly failed on first filling of the reservoir in 1976. To determine what impacts occurred in this upstream canyon reach (from the filling of Teton Reservoir and subsequent failure of Teton Dam), a geomorphology and river hydraulics study was completed by Reclamation during 1997-2000, more than 20 years after the dam failure. When Teton Dam failed, the reservoir was 270 feet deep (at the dam) and drained in less than six hours. The filling and the subsequent rapid draining of the reservoir triggered more than 200 landslides in the river canyon that was inundated by the former reservoir.”  “The failure of Teton Dam resulted in the loss of 11 lives and millions of dollars in property damage.”  Source:  U.S Bureau of Reclamation, “The Failure of Teton Dam.”

For more on the unstable geology at the Black Rock Dam site, click here.