Streambank morphology and cattle grazing in two montane riparian areas in western New Mexico

Abstract

Streambank morphology plays an important role in the ecosystem functions of stream and riparian areas. Large gaps remain in our understanding of the effects of livestock grazing on southwestern stream channels. The purpose of this study was primarily to evaluate the effects of different grazing intensities and different seasons of use on streambank morphology in two montane riparian areas in western New Mexico. We did not find significant larger-scale changes to streambanks over the duration of the study. In contrast, we found many smaller-scale changes that had taken place following cattle grazing. Because the smaller-scale changes we observed were not associated with other indicators of streambank alteration such as bank collapse, widening of the active channel, plant community change, or other larger-scale changes, we conclude that the smaller-scale changes we observed were part of the normal geomorphological adjustments made by streambanks and did not ultimately contribute to lasting streambank morphological change. We also stress that care needs to be given to the selection of appropriate response variables when examining streambank change. Livestock can potentially have large impacts on streambanks, and understanding the effects of grazing on streambank morphology is important in order to make good management decisions.