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
Steamboats of the Colorado River to make only two trips with forty tons in that time. Trips farther up river to the vicinity of Fort Mohave took at least twice as long. The same difficulty plagued the "Colorado" carrying cargo between the estuary and Arizona City. By the fall of 1863 there was a backlog of twelve hundred tons of freight at Arizona City or in ships anchored in the estuary waiting to be brought up river. Between ten and fifty tons of ore waiting to be brought down to the estuary at each of the landings up river above Arizona City. Some of this