Guedes, Rafael Marcondes CarvalhoBryan, Karin R.Coco, GiovanniHolman, Roy A.2011-08-102011-08-102011Guedes, R.M.C., Bryan, K.R., Coco, G. & Holman, R.A. (2011). The effects of tides on swash statistics on an intermediate beach. Journal of Geophysical Research, 116, C04008.https://hdl.handle.net/10289/5559Swash 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.application/pdfenCopyright 2011 by the American Geophysical Union.intermediate beachJournal Article10.1029/2010JC006660