Debris Flows in Grand Canyon National Park, Arizona: Magnitude, Frequency and Effects on the Colorado Riverby Theodore S. Melis, U.S. Geological Survey, Tucson, United States,
Robert H. Webb, U.S. Geological Survey, Tucson, United States,
Document Type: Proceeding Paper
Part of: Hydraulic Engineering
Debris flows are recurrent sediment-transport processes in 525 tributaries of the Colorado River in Grand Canyon. Arizona. Initiated by slope failures in bedrock and (or) colluvium during intense rainfall, Grand Canyon debris flows are high-magnitude, short-duration floods. Debris flows in these tributaries transport very large boulders into the river where they accumulate on debris fans and form rapids. The frequency of debris flows range from less than 1 per century to 10 or more per century in these tributaries. Before regulation by Glen Canyon Dam in 1963, high-magnitude floods on the Colorado River reworked debris fans by eroding all particles except large boulders. Because flow regulation has substantially decreased the river's competence, debris flows occurring after 1963 have increased accumulation of finer-grained sediments on debris fans and in rapids.
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