October 20, 2014
During summer monsoon rains in Arizona many desert areas experience sheetwash. The impact of raindrops on a bare desert surface can easily disturb small sand sized particles, as shown in the insert. Each impact moves the grains in a back and forth motion with little if any net direction. However, on even a subtle slope the small movements of the particles and water will result in a downslope movement -- sheetwash. Without vegetation to hold the soil and absorb water, bare surfaces such as these are susceptible to higher rates of erosion as well as to flooding.