Abstract
Rock particles in debris flows and other geophysical granular flows are reduced in size through abrasion and
fragmentation. A better understanding of the controls on particle wear in geophysical granular flows is needed
for inferring flow conditions from flow deposits, estimating the initial size of sediments entrained in the flow,
modeling flow dynamics, and mapping hazards. We used three rotating drums to create laboratory granular
flows. Drum diameters range from 0.2 to 4.0 m, with the largest drum able to accommodate up to 2 Mg of
debris, including boulders. We began the experiments with well-sorted, angular coarse particles in clear water.
After each 0.25 km of travel distance, we quantified the particle size distribution. Rates of coarse particle
wear, and production of fragments and fine particles scaled with the rate of energy expenditure per unit bed
area, or unit drum power. We used this power scaling to estimate the rate of particle breakdown in a debrisflow
dominated catchment in the Sierra Nevada, California.
