| This research examines the influence of geomorphic processes on downstream hydraulic geometry relationships in the northern Sangre de Cristo Range, Colorado. Large calibre bed material delivered to stream channels by mass-wasting, past glacial and past glacio-fluvial processes profoundly affect stream dynamics and, therefore, downstream hydraulic geometry relationships.; A total of 96 stations are measured: 32 mass-wasting deposits, 32 on till deposits and 32 on outwash deposits. Field measurements include channel cross-section measurements, slope and bed material size and roundness. Derived data include bankfull width, mean depth, mean velocity and discharge, and sorting. Data from topographic maps include elevation, drainage basin area and stream length.; Downstream hydraulic geometry relationships are significantly related to bankfull discharge, but not to stream length. Bankfull mean depth has the highest rate of increase with bankfull discharge while bankfull width has the lowest rate of increase.; Analysis of bed material at each station suggests the following characteristics. First, sorting and roundness are significantly related to stream length but not to bankfull discharge. Second, particle size is generally significantly related to bankfull discharge, but not stream length. Finally, the coarsest fraction of the bed material is immobile at bankfull stage.; Downstream hydraulic geometry relationships are better explained by the addition of a particle size variable. In general, d{dollar}sb{lcub}95{rcub}{dollar} exerts the greatest influence on these relationships. Bankfull width consistently increases with particle size for all groups examined. Bankfull mean depth increases and bankfull mean velocity decreases with particle size for streams flowing over mass-wasting deposits and till deposits. As particle size increases, so does protrusion with flow.; Bed material characteristics are significantly different between material generated by mass-wasting, past glacial and past glacio-fluvial processes. Particle size is largest for mass-wasting generated material and smallest for outwash deposits. Outwash deposits are better sorted and more rounded compared to the other two groups.; In conclusion, streams in the study area have only limited influence over their channels. Their effectiveness is governed by their competency to entrain large calibre bed material derived from mass-wasting, and past glacial processes. |
