Date of Award:

5-2016

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Department name when degree awarded

Watershed Science

Committee Chair(s)

Patrick Belmont

Committee

Patrick Belmont

Committee

Peter Wilcock

Committee

Charles Hawkins

Abstract

Erosion, transport and deposition of fine sediment (clay, silt and fine sand) influence the form and function of river systems. Excess suspended sediment degrades stream ecosystems and is implicated as a leading cause of water quality and aquatic life impairment. Therefore, understanding the factors that control fine sediment transport patterns is an interesting topic for basic science and one that has important management and policy implications.

In this study, we sought to understand how attributes of the landscape and channel network might control the shape, steepness and vertical offset of the relationship between river discharge and suspended sediment. Watershed and channel attributes included in our analysis were high-resolution topography, geology, soil erodibility, climate, and land use. Our results indicated that land use within the watershed most controlled sediment concentrations at low and moderate flows, with higher percentages of agriculture and lower forest cover associated with higher sediment concentrations. Conversely, the steepness, or rate-of-change, of the discharge-suspended solids relationships was dominantly affected by the topography and landforms near the channel. Rivers with high sediment concentrations at high water discharge were those with steep channel gradients and with bluffs and tall banks near the channel, which are likely important sediment sources. These results support previous findings that sediment load reduction at high flows may be best achieved by management approaches aimed at reducing the magnitude and frequency of high flows and controlling erosion from near-channel sediment sources, rather than additional regulations on land use aimed at reducing erosion from upland soils.

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