The effects of tides on swash statistics on an intermediate beach
| Autor: | Karin R. Bryan, Rafael Marcondes Carvalho Guedes, Roy. A. Holman, Giovanni Coco |
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| Rok vydání: | 2011 |
| Předmět: |
Atmospheric Science
Soil Science Aquatic Science Surf zone Oceanography Waterline symbols.namesake Geochemistry and Petrology Earth and Planetary Sciences (miscellaneous) Geomorphology Earth-Surface Processes Water Science and Technology Shore geography geography.geographical_feature_category Ecology Paleontology Shoal Breaking wave Forestry Geophysics Space and Planetary Science symbols Crest Significant wave height Geology Seismology Swash |
| Zdroj: | Journal of Geophysical Research. 116 |
| ISSN: | 0148-0227 |
| Popis: | [1] 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. |
| Databáze: | OpenAIRE |
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