1996 Controlled Flood from Glen Canyon Dam Rebuilt Grand Canyon Sandbars

During a week-long operation in 1996, scientists coordinated with the U.S. Geological Survey to open Glen Canyon Dam and generate a controlled flood that reached flow rates of 45,000 cubic feet per second. The surge, lasting about seven days, was designed to transport sediment downstream and replenish sandbars that had deteriorated after the dam trapped most of the river’s sand in Lake Powell. Monitoring showed that the flood wave redistributed material onto riverbanks and existing bars, providing temporary habitat and camping space for river users.

While the release did not permanently restore the canyon’s historic flood regime, it demonstrated that dam operations could be leveraged for ecological benefit. Later releases have applied lessons from this trial to improve sediment movement and sandbar longevity.