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
Course of the Colorado River Topock Marsh in Topock Gorge and widens into Lake Havasu, formed by Parker Dam. Lake Havasu provides recreation as well as the home of the retired U.K. London Bridge in Lake Havasu City, Arizona, now the New London Bridge. Near Parker Dam are the first two major diversions of the lower Colorado: the Colorado River Aqueduct, which travels west to Los Angeles and San Diego, California; and the Central Arizona Project, which sends water east towards Phoenix and Tucson, Arizona. The intermittent Bill Williams River joins the Colorado from the east in Lake Havasu, just above Parker Dam. The river