Please use this identifier to cite or link to this item: https://hdl.handle.net/11681/22923
Title: Nearshore tidal and nontidal currents, Virginia Beach, Virginia
Authors: Harrison, Wyman, 1931-
Brehmer, Morris L.
Stone, Richard B.
Keywords: Ocean currents--Virginia--Virginia Beach
Ocean waves--Atlantic Ocean
Publisher: Coastal Engineering Research Center (U.S.)
Series/Report no.: Technical Memorandum;no. 5
Abstract: Abstract: Simultaneous measurements by Eulerian and Lagrangian methods were made continuously between 30 July and 5 August 1962. The survey zone extended southward along the shore 11.5 km (7.2 mi.) from the Cape Henry Light and offshore for a distance of 1.4 km (0.87 mi.). Three Roberts Radio Current Meter Stations were established along the seaward margin of the zone; five stations were established on shore for longshore-current and wave measurements. Wave heights for the 7-day period ranged between 0.3 and 0.5 m, wave lengths between 14 and 159m, and wave energies between 6.3 and 553 kg-m/m. Winds were less than 16 mph during the period, total wind movement & being greatest from the east and southeast. Shoaling waves made angles with the shore line that should have resulted in a southward longshore current during 48 of 69 observations, on a coast uninfluenced by other currents. Direction of longshore current movement was measured as northerly, however, in 55 instances, owing to tidal and nontidal currents. Current meter observations at Cape Henry and just south of Rudee Inlet revealed semi-diurnal tidal currents that were roughly reversing on the flood and rotary on the ebb, at the surface. A meter midway between the Cape Henry and Rudee Inlet meters indicated reversing currents at the surface, as did all intermediate depth and near-bottom meters. When 280 returns of neutrally-buoyed drift bottles, released over a year's period, are integrated with detailed current-survey data, a circulation model can be constructed. This model confirms earlier speculation that the nontidal drift describes a clockwise eddy movement south of Cape Henry. The southern limit appears to be near Rudee Inlet. Diffusion was investigated in one of the tidal currents during ebb flow by continuous tagging with rhodamine-B dye at the rate of 0.7 g/sec and by monitoring dye concentrations with fluorimeters. A log-log plot of a "concentration ratio," for values of x between 800 and 3800 m, fitted an x-1 relationship where c equals peak dye concentration, M equals rate of dye discharge (g/sec), D equals layer depth (m) and x equals distance along the axis of the plume. Neighbor diffusivity, F (£) had a minimum value of 316 cm2/sec and the coefficient e , in .F (£) = e£4/ 3 had the minimum value of 0.062.
Description: Technical Memorandum
Rights: Approved for public release; distribution is unlimited.
URI: http://hdl.handle.net/11681/22923
Appears in Collections:Technical Memorandum

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