The Fluvial Geomorphology of the Upper Animas River Basin, Colorado

Abstract

Recent research identifies mountain environments as especially important for monitoring environmental changes related to both global climate fluctuations and human activities. This dissertation contributes to the numerous studies on human-Earth relationships and addresses a lack of detailed knowledge of spatial relationships in small mountainous headwater basins. The specific research questions addressed herein include: Are the fluvial processes within the watershed representative of the fluvial forms? Can existing morphology classification schemes predict channel form from collected raw data? How do the sediments within the headwater streams reflect change through space? Data collected in the field from streams within the Upper Animas River basin combined with statistical techniques and the use of geographic information science software allowed for the determination of a basin-scale view of the fluvial forms and processes at work in this small mountain watershed. A multivariate analysis of historical mining effects on fluvial forms revealed a statistically significant relationship between mining activities and channel entrenchment. An investigation of the utility of existing channel classification systems detailed the difficulty of classifying the morphology of headwater streams and suggested that existing schemes should only be used in this basin with caution. Data on the river sediment landscape were calculated and mapped in order to investigate downstream spatial patterns. Analyses determined a weak relationship between channel roughness, sediment size, and sediment shape as compared to drainage area due perhaps to the unique nature of mountain streams and the extreme influence of coupled hillslope-fluvial processes. Overall the rivers of this basin are thought to be in a non-equilibrium state.