Publication Date

8-2023

Date of Final Oral Examination (Defense)

April 2023

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Geophysics

Department

Geosciences

Supervisory Committee Chair

Jacob Anderson, Ph.D.

Supervisory Committee Member

James McNamara, Ph.D.

Supervisory Committee Member

Elowyn Yager, Ph.D.

Abstract

Rivers, streams, and tributaries play a critical role in the global water cycle and their dispersion of freshwater is essential for widespread human consumption, crop irrigation, waste management, and hydropower generation. Currently, there is a need for innovative, non-invasive, and low-cost methods of surface freshwater discharge gauging. With careful site selection, recording the acoustics produced by streamflow could be used reliably and inexpensively to infer changes in local discharge. An important knowledge gap currently preventing the use of acoustics for stream gauging is the unknown relationships by which stream sounds depend on discharge and stream morphology. To address this, I recorded and characterized sound and infrasound produced by morphologically unique features of the Boise River and Dry Creek in Southern Idaho across multi-year spans. Using a flume and a custom-made adjustable plunge-pool apparatus, I recorded acoustics produced by plunge-pool flow conditions at several scales of discharge and morphology to understand how channel and flow structure influence acoustic properties. While past research has evaluated the effects of discharge and flow structure on acoustic signals separately in either field or laboratory settings, this study investigates these variables jointly in natural, dam regulated, and laboratory fluvial settings. To elucidate the roles of discharge and flow structure on acoustic signals, this study examined sound from eight stream-gauged, morphologically diverse study sites, a discharge-variable morphologically constant flume plunge-pool, and a morphologically variable discharge-constant plunge-pool. Rising downstream depth at a plunge-pool strongly influences both acoustic power and frequency. The initial drop height of a plunging jet and the width of its receiving pool were found to clearly influence acoustic signals, while the width of a plunging jet may also play a role in acoustics. Using sound to infer discharge works well at step features with low width/depth ratios, at high width/depth ratio step features with negligibly changing morphologies, and sometimes works at riffle features and morphologically variable step features. At several field sites, we observed power to increase with flow until a certain discharge threshold, where it either does not change or decreases with rising discharge. With additional studies in morphologically diverse channels such as bedrock and cascade, acoustics may be used as a non-invasive, inexpensive, and accurate hydrometric tool to help fill global surface water gauging gaps.

DOI

https://doi.org/10.18122/td.2105.boisestate

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