From the Arizona Geology Blog:
On Saturday, Aug. 16, 2008, in the late afternoon and evening, the northern Arizona high country received heavy rainfall that resulted in partial flooding of Supai Canyon. Supai Canyon is a popular destination for hikers and campers due to the presence of majestic water falls in the area. Supai Village is the home of approximately 400 year round residents.
The Grand Canyon Regional Communications Center received information from Western Rivers Adventures that five unmanned rafts were observed floating down the Colorado River with personal floatation devices and other supplies still onboard. National Park Service employees believed the crafts belonged to a private boating party of 16 individuals. The entire party was located uninjured and stranded on a ledge at the confluence of Havasu Creek and the Colorado River.
At 6 a.m. Sunday morning, Coconino County Officials learned that the Redlands Earthen Dam broke, allowing a high volume of water to rush down Cataract Canyon in a westerly direction eventually feeding into Supai Canyon. Heavy flooding in Supai Canyon and the potential for additional flooding has necessitated the evacuation of an undetermined number of campers and approximately 400 full time residents.
Rescuers are attempting to locate visitors who were staying at the Supai Camp Ground located above Havasu Falls and escort them to a safe landing zone in Supai Village. Campers and full time residents will be flown to Hilltop by Arizona Department of Public Safety Helicopters and Arizona National Guard Black Hawk Helicopters. Evacuees will be bused to an American Red Cross shelter located at the Hualapai Tribal Gymnasium in Peach Springs Arizona.