Characterization and Prediction of Hyporheic Flow Induced by Bars in Gravel Streams
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Authors
Button, Avneet
Date
Type
thesis
Language
eng
Keyword
Hyporheic , Gravel Stream , Gravel Bar , Darcy's Law
Alternative Title
Abstract
Hyporheic flows induced by bars in gravel streams are vital to the overall health of a river
but can also be the primary mechanism for contamination to fish habitats. It is therefore of
primordial importance to characterize such hyporheic flows under varying hydraulic and
morphological conditions, and develop methods and tools for their prediction. This thesis
is intended as a contribution to these ends.
The work involves an extensive series of laboratory experiments, guided by a
dimensional analysis of the phenomenon under consideration, and revealing a possible
dependency of vhyp /k on Δ/Λ and Δ/hav. Hyporheic flows were visualized in a gravel bar
and underlying substrate constructed in a 21 m long flume under nine different test cases
(combination of varying free surface flow depths (18, 15 and 12 cm) and bar lengths (1.0,
1.6 and 2.5 m)). Dye injections were recorded and processed to reveal hyporheic flow paths
and velocities. Hyporheic flows upstream and downstream of the bar top traveled
longitudinally, converged at the flow divide line and upwelled into the stream flow at the
flow divide line. For any given bar, smaller free surface flow depths produced hyporheic
flows that penetrated deeper into the gravel and emerged into the stream flow further
downstream. Hyporheic flow was always turbulent with the 1.0 and 1.6 m long bars
producing similar hyporheic flow velocities that were approximately 30% higher than those
produced by the 2.5 m long bar. The present analysis shows that for any given value of
Δ/Λ, vhyp /k varies with Δ/hav by first increasing from 0 to a maximum at Δ/hav ≈ 0.45, and
then decreasing.
Although Darcy’s equation is only valid for laminar flows, a simple model based
on this equation was developed for determining hyporheic flows through a gravel bar with
the goal of investigating if Darcy’s equation can provide any reasonable approximation of
hyporheic flow. The computational grid represents the gravel bar and underlying substrate
of the laboratory experiments. The model produced hyporheic flow paths which were in
good agreement with the laboratory experiments. However, the hyporheic flow velocities
were greatly underestimated. In spite of this, the model offers a quick and computationally
simple method for preliminary assessments in practical applications.
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Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.