The effects of channel morphology on the mobility and dispersion of sediment in a small gravel-bed stream

The role of channel morphology in sediment transport is poorly understood due to the complexity of the interactions between morphology, sediment characteristics and flow. A better understanding of the ways in which channel morphology affects sediment transport at all scales and under varying flow conditions can improve predictions of channel behavior and provide insights for better stream restoration applications. This study aimed to capture the effects of morphology on bed mobility and sediment dispersion in a small gravel-bed stream through the use of a 10 year tracer dataset. The characterization of bed mobility and sediment dispersion conducted at three spatial scales (the reach, morphological unit and local scale), revealed the importance of scale when examining the role or morphology on sediment transport. East Creek was found to be in conditions of marginal sediment transport, remaining near the critical conditions for sediment mobilization the majority of the time, and falling within a low sediment transport regime common in small gravel-bed streams. Both bed mobility and tracer travel distances increased with increasing flow conditions, and measures of cumulative flow energy had stronger relations to both variables than peak discharge. Grain size was not found to play no role in bed mobility or travel distance in East Creek. At the reach scale, morphology did not affect bed mobility, and influenced the travel distance of tracers only during high flows, or when averaged over long time periods. Although burial rates were high, burial depths were shallow, and burial showed no relation to flow or mobility. At the morphological unit scale, differences were observed in the rate of increase of bed area under mobility with increasing flow between reaches and between morphological units. Finally, at the local scale, bed mobility was highly localized and sporadic. Results of this study allow for the description of the role of morphology on bed mobility and sediment dispersion in a low sediment transport regime and throughout various spatial and temporal scales. Further research opportunities include the exploration of the role of morphology on bed mobility and sediment dispersion in a variety of morphological and sediment transport settings.Arts, Faculty ofGeography, Department ofGraduat