Standing edge waves on a pocket beach
H. Tuba Ozkan-Haller, C. Vidal, I. J. Losada, R. Medina, M. A. Losada
Journal of Geophysical Research, Vol.106, nº C8, pp.16,981-16,996 [Aug. 2001]

Abstract:
Field measurements of edge waves obtained on a narrow pocket beach are described. Ile beach (named Usgo is located on the north coast of Spain immediately to the west of the city of Santander and is exposed to the Atlantic ocean. Results from a longashore array of current meters located in about 3 m of water depth are presented with the objective of analyzing the edge wave field on this beach. Frequency spectra of longashore velocities show that the edge wave field on this pocket beach displays several significant peaks. Ilia is in contrast to observations on open coastal beaches [e.g. Oltman-Shay and Guza, 19871 which show the existence of a broad banded edge wave field. We isolate four frequency peaks and analyze the longshore variation of the motions at these frequencies and find convincing evidence of a nodal structure. Utilizing the measured bathymetry, we compute the theoretical wavelengths of edge waves at the dominant frequencies using a numerical solution method of the shallow water equations by Howd et at [1992). We find that edge waves at these frequencies satisfy the standing wave resonance condition, i.e. the width of the beach corresponds closely to an Integer multiple of the computed half-wavelengths. In addition, assuming perfect sidewall reflections, the theoretical nodal locations closely correspond to those inferred by the measurements. We conclude that discrete standing edge waves that are a result of resonances related to the longshore width of the beach are present on Usgo Beach