EFFECT OF VEGETATION ESTABLISHMENT ON BANK STABILIZATION IN COLORADO RIVER TRIBUTARIES WITHIN GRAND CANYON NATIONAL PARK

Flash flooding is a common occurrence in the tributaries of the Colorado River and often have major impacts on tributary floodplains. Native plant and animal species have developed adaptations to the intensity of these floods and to exist in a dynamic equilibrium within the desert environment. In July and August of 2014 Shinumo Creek experienced two back to back flash floods that denuded the creek banks of vegetation and changed the dominant stream bed composition from coarse gravel to fine pebbles. The creek is now in a transitional phase with an unknown trajectory and final equilibrium state. Vegetation that establishes during this critical time will benefit the creek through bank stabilization, but could also have the adverse effect of reducing stream flow. Schenk and Tobin (2015, GSA abstract 331-10) found that the stream does not currently have the competency during regular flows to move the finer sediment that has settled in the stream, therefore the reestablishment of vegetation on the banks could further hamper the creek’s ability to return to its previous state. The purpose of this research is to explore the effect of vegetation removal on stream flow and related bed sediment flux following the flood. Observations from repeat photography (2015, 2016) show an increase in vegetation establishment at 9 sites within the riparian area of the creek. The influence of vegetation on flow was compared between Shinumo Creek (pre and post flood) and 5 other Colorado River tributaries (Little Colorado River, Bright Angel Creek, Kanab Creek, Paria River, and Havasu Creek) to determine changes in hydrograph trends related to riparian vegetation density.