Events & Media

Presents

A PhD Dissertation Defense

"Fluvial Processes Affecting the Texture of a Gravel Bed
with an Emphasis on Salmon Spawning Habitat"

Matthew Armand Meyers
PhD Candidate
Bren School

Wednesday, May 24, 2017
10:00 a.m.
Bren Hall 1424

Faculty Advisor: Tom Dunne
Committee Members: Derek Booth, James Frew, Ed Keller

Abstract
The coarse texture of a gravel bed is maintained by flow strengths capable of moving (i.e., entraining) the gravel and removing fine sediments, thereby providing loose substrate that enhances its ability to conduct flow (i.e., its hydraulic conductivity). I examine these processes using field measurements to explain the variability in (i) the rate of change in the proportion of a gravel size fraction entrained as a function of flow strength and (ii) the rate of decrease in hydraulic conductivity as a function of the cumulative transport of fine sediment that depends on flow level. Two approaches are demonstrated to provide the flow strength capable of entraining the least resistant through the most resistant grains, thereby providing new methods to measure the flow strength that is capable of entraining a given fraction of the bed. Using artificially constructed salmon nests, the hydraulic conductivity of sediment mixtures is demonstrated to depend on fine sediment bed load transport as a function of flow rate. This work provides additional understandings of the relationship between flow and bed texture maintenance processes and useful tools for managing gravel bed rivers.

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