Open AccessThe effects of tides on swash statistics on an intermediate beach
Author(s) -
Guedes R. M. C.,
Bryan K. R.,
Coco G.,
Holman R. A.
Publication year - 2011
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010jc006660
Subject(s) - swash , geology , shoal , surf zone , infragravity wave , wave height , shore , submarine pipeline , dissipation , accretion (finance) , breaking wave , plage , oceanography , physics , geomorphology , wave propagation , mechanical wave , longitudinal wave , quantum mechanics , astrophysics , thermodynamics
Swash hydrodynamics were investigated on an intermediate beach using runup data obtained from video images. Under mild, near‐constant, offshore wave conditions, the presence of a sandbar and the tidally controlled water depth over its crest determined whether most of the incoming waves broke before reaching the shoreline. This forced a change in the pattern of wave energy dissipation across the surf zone between low and high tide, which was reflected by changes to swash on time scales of a few hours. Significant runup height ( Rs , defined as 4 times the standard deviation of the waterline time series), was found to vary by a factor of 2 between low tide, when most of the waves were breaking over the sandbar ( Rs / Hs ≈ 1.5, where Hs is the offshore significant wave height) and high tide, when the waves were barely breaking ( Rs / Hs ≈ 2.7). The increase in wave energy dissipation during low tide was also associated with changes in swash maxima distribution, a decrease in mean swash period, and increasing energy at infragravity frequencies. Bispectral analysis suggested that this infragravity modulation might have been connected with the presence of secondary waves.