We used a before-and-after study design to examine effects of changes in cattle grazing practices on channel stability in Muddy Creek, an arroyo in the Colorado River headwaters. The changes in grazing practices were abrupt and focused on keeping cattle out of the riparian zone and increasing herd movement. We digitized 620 meander loop cutoff geometries within the alluvial valley bottom of Muddy Creek and used the meander loop cutoff rate as a broad measure of channel stability. Poisson regression modeling of meander loop cutoff rate indicated that the change in grazing practices caused a decline in meander loop cutoff rate that was on the scale of an order of magnitude and independent of other hydroclimatic and human-caused factors. The polygon data released here was used to define the area of interest for digitizing meander loop cutoff geometries.