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Date of Award

Summer 2023

Document Type

Masters Thesis

Department or Program Affiliation

Geology

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Grossman, Eric E.

Second Advisor

Mitchell, Robert J. (Geologist)

Third Advisor

Ponton, Camilo

Abstract

Understanding nearshore sediment budgets and processes is important for evaluating coastal hazards, habitats, and contaminant fate to enable informed decisions in coastal planning and management. I aimed to evaluate the role of waves in resuspending and redistributing sediments and by proxy contaminants in the urban/estuarine Bellingham Bay, and better understand the transport and rate of fluvial sediment moving through the nearshore. I integrated analyses using camera-mounted sediment traps, seafloor grain-size data, short-lived radioisotopes, and other fluvial, physical oceanographic, and wind data. I paired cameras with sediment traps, to identify the timing and rate of sedimentation on the seafloor at hourly timescales. The camera imagery helped to differentiate the relative contribution of waves and direct dispersal of fluvial sediment. Resuspension of bed sediments by wind-waves accounted for most of sedimentation in traps across the nearshore zone. Using wind and wave measurements, bed shear estimates, and sedimentation observations, I identified threshold conditions for bed sediment resuspension at different settings of the Bay. Using a historical wind record and reconstructed wave records, I estimated that the threshold for bed mobilization was met for >1000 hours/year at delta sites exposed to prevailing storms. Along the more protected urban shoreline, the focus area of contaminant remediation projects, I found that bed mobilization thresholds were met for hundreds of hours/year. These findings have implications for contaminant availability, as my data suggested that sediment flux of resuspended material off the shallow seafloor was usually of much greater magnitude than the rate at which new sediment was deposited.

Type

Text

Keywords

sediment, sedimentation, time-lapse, delta, estuary, contaminants, waves, resuspension, puget, salish

Publisher

Western Washington University

OCLC Number

1394051093

Subject – LCSH

Sediment transport--Washington (State)--Bellingham Bay; Marine sediments--Washington (State)--Bellingham Bay; Sedimentation and deposition--Washington (State)--Bellingham Bay; Sedimentation analysis

Geographic Coverage

Bellingham Bay (Wash.)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

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