Geomorphology and Dynamics of a Sand Wave in Lower Chesapeake Bay, Virginia

<p>A single, more or less isolated, sand wave in a sand wave field recently discovered in the lower Chesapeake Bay, Virginia, was studied intensively for morphology, sedimentology and in terms of dynamic processes. The morphologic investigation consisted of bathymetric surveys of the sand wave field and the specific sand wave. Twenty-five grab samples and four box cores were obtained from different segments of the feature studied. Textural parameters of the samples were determined, and a multivariate technique was utilized to identify subenvironments on the feature. The box cores provided information on the internal structure of the sand wave.</p> <p>Observations of near-surface currents, and turbulent shear stresses at a level 5 cm above the bottom were made at five stations distributed along the profile of the sand wave. Simultaneously, vertical profiles of density were measured. Time series analysis of the shear stress data at 5 cm above the bed revealed three types of constituents: (a) long period trends, (b) wave-associated events, and (c) turbulence. The turbulent part of the record was found to be highly reduced in comparison with the other two components. Spectral analysis revealed that the energy of the horizontal component of the flow was smaller than the energy for the vertical component of the flow. Suspended sediments and stable density stratification are known to reduce turbulence, and doubtless have great effect in the present instance; however, the most affected was found to be u and not w as would have been expected.</p> <p>A decrease in main flow velocity due to the three-dimensional shape of the feature is believed to result in a strong reduction in the horizontal component of the flow, as well as in the shear stress.</p> <p>In the case of a more-or-less isolated feature, the flow can follow, or partly follow, a path of avoidance around the feature. The integrated results of the study suggested that the sand wave is a "solitary" bedform, originally formed by ebb currents, and presently is in static equilibrium with the circulation pattern.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Ocean & Earth Sciences

Year dc:date.available

1981

Author dc:creator

• Perillo, Gerardo Miguel Eduardo

Contributors dc:contributor

• John C. Ludwick
• Chester E. Grosch
• Dennis A. Darby
• George F. Oertel

• Chesapeake Bay
• Sand waves
• Geomorphology
• Geology

Statement dc:rights

• <p>In Copyright. URI: <a href="http://rightsstatements.org/vocab/InC/1.0/">http://rightsstatements.org/vocab/InC/1.0/</a> This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).</p>

Repository record dc:identifier

https://digitalcommons.odu.edu/oeas_etds/149

OAI identifier oai:identifier

oai:digitalcommons.odu.edu:oeas_etds-1149