Risks to the Glen Canyon Dam that the resulting flood would scour the bottom few hundred feet of the Grand Canyon, overtop Hoover Dam, and cause severe damage all along the lower Colorado River. In the event of a complete dam failure with Lake Powell at high pool, about of water would surge out of Lake Powell at an initial depth of over . Downstream communities and perhaps every dam along the river, excluding possibly Hoover Dam, as well as riverside lowlands, would be inundated or severely damaged. Located downstream from Glen Canyon Dam are Hoover Dam forming Lake Mead, Davis Dam forming Lake Mohave, Parker
Indigenous peoples of the North American Southwest the border of Texas and Mexico. Several Spanish explorers described this culture which was related to or derivative from the Jornada Mogollon. Between 700 and 1550 CE, the Patayan culture inhabited parts of modern-day Arizona, California and Baja California, including areas near the Colorado River Valley, nearby uplands, and north to the vicinity of the Grand Canyon. The Fremont culture inhabited sites in what is now Utah and parts of Nevada, Idaho and Colorado from 700 to 1300 CE. Archaeologists use cultural labels such as Mogollon, Ancestral Pueblo peoples, Patayan, or Hohokam to denote cultural traditions within the prehistoric American