Dam Failure Case Study: Glen Canyon Dam (Arizona, 1983)

In the summer of 1983, Glen Canyon Dam and its reservoir, Lake Powell, experienced higher-than-normal inflows. Despite National Weather Service forecasts predicting high spring runoff, Lake Powell was maintained at near 100% capacity, leaving very little storage capacity to attenuate the high inflow rates. On June 2, Glen Canyon Dam began releasing flows through the left spillway. On June 6, the dam’s operators heard vibrations coming from the spillway tunnel and observed material being discharged from the outlet. The configuration of the dam’s two spillways had left them vulnerable to damage from cavitation due to the very high velocities within the spillway tunnels. There was a very real concern that erosion of the spillway tunnels could undermine the dam’s foundation and cause the entire dam to fail. Over the following weeks, the dam’s operators regulated discharges through the damaged spillways in order to prevent uncontrolled discharge or even overtopping of the dam. Throughout the whole ordeal, the operators knew that damage to the spillways was continuing, but unsure of the rate or extent of the damage. Ultimately, the operators were successful in passing the high flows and the spillways at Glen Canyon Dam were repaired and retrofitted to prevent cavitation from reoccurring in the future.