WAVE ENERGY REFLECTION AT A ROCKY COAST
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Authors
O'Brien, Kevin J.
Subjects
reflection
rocky shoreline
bottom friction
dissipation
rocky shoreline
bottom friction
dissipation
Advisors
MacMahan, James H.
Date of Issue
2019-12
Date
Dec-19
Publisher
Monterey, CA; Naval Postgraduate School
Language
Abstract
Wave energy reflection, defined as the ratio of offshore to onshore energy flux, R2, of surface gravity waves from a rough rocky shoreline, was investigated from two individual 15-day Acoustic Doppler Current Profiler (ADCP) deployments at Hopkins Marine Station in Monterey Bay, California. The first was deployed in 9 m water depth, located 100 m seaward of the rocky shoreline, and the second was deployed in 2.5 m water depth, located approximately 6 m from the shoreline. The mean R2 for both deployments was ~0.08, suggesting minimal reflection. R2 statistically decreased (at 95% significance) by 0.05 during the transition from low to high tide. R2 was found to be independent of onshore wave energy. The mean direction of the incoming and outgoing waves was approximately equal and opposite, though the outgoing waves displayed more directional variability. This increase is believed to occur from the alongshore variability of the shoreline that was weakly correlated with tidal elevation. These R2 are similar to observations at rough coral reefs and breakwaters. It appears that the primary reflector is the shoreline and not scattering by the rough subaqueous bottom. Wave dissipation plays a larger role than wave reflection at this rocky shoreline, which may influence biological community structures and nutrient transport.
Type
Thesis
Description
Series/Report No
Department
Oceanography (OC)
Organization
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NPS Report Number
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Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.