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September 20, 2012

Development of sediment budgets at multiple scales

Name: Susannah Erwin
Major: Watershed sciences
Department: WATS
Graduation date: Fall 2012 (PhD)
Title: Development of sediment budgets at multiple scales: Investigations into the influence of sediment supply on channel morphology

Channel morphology in alluvial rivers is determined by the flow of water and sediment, and the characteristics of the materials making up the channel boundary. Many modern river management problems depend upon our ability to predict channel behavior in response to changes in the delivery of water or sediment. Sediment delivery to a river may be altered by natural or human-caused changes, such as changes in land use in the watershed, construction and operations of dam, forest fires, or climate change. Understanding and predicting the effects of these alterations is important because changes in sediment supply and transport may alter river characteristics, impact riverine habitat, and affect aquatic organisms. Sediment budgets - an accounting of the sediment delivered to, transport through, and exported from a river network - are a fundamental tool used to understand how rivers respond to perturbations in sediment supply. Here, I developed sediment budgets at three different spatial and temporal scales in order to investigate the influence of sediment supply on channel form. In this dissertation I present (1) a large-scale field study of systemic change on the Snake River in Grand Teton National Park (GTNP); (2) an intermediate-scale field study on a section of the reconfigured Provo River in Heber Valley, UI, where gravel is actively accumulating; and (3) a small-scale, physical experiment of point bar response to changes in sediment influx. Together, these three studies highlight the inherent challenges and uncertainties encountered when developing sediment budgets. Additionally, the work furthers our understanding of how rivers respond to a change in the delivery of water or sediment.