Date of Award

Summer 8-18-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Kimberly Huguenard

Second Committee Member

Lauren Ross

Third Committee Member

Neil Fisher

Abstract

Coastal erosion presents a growing issue to shorelines around the world and is especially harmful to Maine, a region where sea-level rise is higher than the global average. Green and hybrid coastal defense strategies are being implemented around the country to provide sustainable, habitat-friendly solutions to erosion control. Maine is a hotspot for commercial aquaculture, with an estimated $13.6 million economic impact. This study looks to bridge the gap between Maine aquaculture and the living shorelines initiative, by determining the wave attenuating properties of submerged oyster cages. The project will be able to inform local oyster farmers, resource planners, and engineers on the potential for submerged oyster farms to attenuate wave energy. This study aims to explore the idea of a working waterfront, where coastal resilience and sustainability are tied in with economic opportunity, all while encouraging the protection of habitats and water resources. This study utilizes field observations from several SOFAR Spotter Buoys deployed for 28 days that were positioned before and after a long line of bottom lying oyster cages to measure wave decay in a protected inlet of Casco Bay in the Gulf of Maine. These observations were combined with water level data from a HOBO water level logger to assess the effect of tidal fluctuations. A computational fluid dynamic model complemented the field observations, which allowed for the characterization of the longitudinal wave decay along the farm. The wave attenuation mechanism was determined, as well as the wave-induced setup in mean water levels. The CFD model is a cut section of a long line of bottom-lying oysters, using DualSPHysics, a smooth particle hydrodynamic model. Wave decay of up to 80% for ~4 second waves was seen over 30 m of oyster cages, where less-steep waves and shorter waves were attenuated more. Added mass drag dominated wave attenuation compared to friction, supported by KC (Keulegan Carpenter Number) values

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