A 4500-Year Record of Large Floods on the Colorado River in the Grand Canyon, Arizona

A sequence of flood deposits left by the Colorado River in the Grand Canyon, Arizona, provides evidence of at least 15 floods with peak discharges greater than 5500 m³sec⁻¹ over the last 4500 yr. Ten floods during the last 2000-2300 yr had discharges greater than 6800 m³sec⁻¹. One flood, 1600-1200 yr ago, had a discharge exceeding 14,000 m³sec-1, a flow rate more than twice the largest gaged flood. This record of flooding is one of the longest for a major U.S. river, and, combined with the gaged record of twentieth century floods, allows determination of the frequency and history of large floods that have affected key aspects of Colorado River geomorphology.