Year of Award

2015

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Geosciences

Department or School/College

Department of Geosciences

Committee Chair

Andrew Wilcox

Commitee Members

Lisa Eby, Marco Maneta

Keywords

confluences, tracers, RFID, PIT tags, sediment routing, dispersion

Subject Categories

Geomorphology | Hydrology

Abstract

Sediment routing in gravel-bed rivers refers to the intermittent transport and storage of bedload particles, where short-duration steps are separated by periods of inactivity. Channel morphology governs sediment routing, but morphologic effects on routing in headwater systems are not well understood compared to lowland systems. RFID tracers are a valuable tool that can be employed to characterize routing processes in headwater channels through individual particle tracking. I present research on coarse sediment transport and dispersion through confluences using sediment tracers in the East Fork Bitterroot River basin, MT. I investigate the following questions: (1) How do sediment routing patterns through headwater confluences compare to those in low-gradient gravel bed river systems? (2) How does routing through confluences compare with theory and field analysis regarding dispersive behavior in non-confluence channel morphologies? I address these questions with tracer displacement data, topographic surveys, and flow measurements through two coarse-bedded headwater confluences. Within the confluence zone, transport occurs along scour hole margins in narrow, efficient transport corridors. Bedload transport is size-dependent in the plane-bed control reach, but not for tracers moving through the confluence zone. At the reach scale, data suggest that particle dispersion is enhanced through confluences relative to non-confluence channels. These results suggest that geomorphically-significant confluences may influence the dispersive evolution of bedload particles across headwater basins.

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© Copyright 2015 Kurt Imhoff