Groin-Associated Rip Currents Measured Using a New Digital Current Meter

<p>Rip currents have often been noted in physical model studies of groins and their effectiveness. Nevertheless, detailed field investigations of rip currents along a groin wall have not been heretofore conducted. A new digital current meter system was designed and built to study the groin-associated rip currents in a test groin compartment at Willoughby Spit, Norfolk, VA. Six ducted impeller current meters are controlled by a data acquisition system that utilizes an onboard microprocessor and solid state memory. The new system provides high quality data on horizontal water velocities associated with wave action. The velocities stored are time mean velocities averaged over one second. The system will make possible future studies of three dimensional flow in the nearshore and coastal zones at relatively low cost.</p> <p>The present study verified the existence of a groin-associated rip current in the test compartment. Measured vertical velocity profiles showed that the near bottom time mean flow was often directed onshore while the time mean flow in the upper levels was nearly always directed offshore. The presence of the rip current reduces groin effectiveness by transporting sediment from the compartment seawards beyond the groin ends. The complex vertical structure of the time mean flow makes the use of depth-averaged velocities to estimate sediment transport in a groin compartment questionable. The flow intensity for both the near botton flow and the upper flow was directly proportional to the wave breaker height and reflects the low wave energy input to this estuarine beach site. Eddies that rotate clockwise were observed at the upstream groin wall relative to the tidal current. The action of these eddies may contribute significantly to sediment scour near the groin ends.</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

1987

Author dc:creator

• Lundberg, Dennis L.

Contributors dc:contributor

• J. C. Ludwick
• G. F. Oertel
• Chester Grosch
• G. Richard Whittecar

• Rip currents
• Measurements
• Digital meter
• Oceanography

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/144

OAI identifier oai:identifier

oai:digitalcommons.odu.edu:oeas_etds-1139