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Standing infragravity waves over an alongshore irregular rocky bathymetry
Author(s) -
Winter G.,
Lowe R. J.,
Symonds G.,
Hansen J. E.,
van Dongeren A. R.
Publication year - 2017
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2016jc012242
Subject(s) - bathymetry , geology , infragravity wave , reef , shore , beach morphodynamics , oceanography , wave height , rip current , surf zone , seismology , geomorphology , sediment transport , wave propagation , sediment , mechanical wave , longitudinal wave , physics , quantum mechanics
Rocky reef coastlines typically feature highly variable and often abrupt cross‐shore and alongshore changes in bathymetry. The effects of this irregular rocky bathymetry on the dynamics of infragravity waves are largely unknown. Most models of infragravity wave dynamics have been developed and validated on smooth alongshore‐uniform bathymetries, which may break down over these highly variable bathymetries. A 2 week field experiment was conducted on a rocky reef‐fringed beach to investigate how the variable bathymetry affects the spatial and temporal variability of infragravity waves. The height of short (sea‐swell) waves decreased over the shallow reef due to breaking, whereas the height of infragravity waves increased toward the shoreline. Both during a storm event ( H m 0 = 2.3 m) and under moderate wave conditions ( H m 0 = 1.0–1.8 m), the infragravity waves formed a persistent cross‐shore standing wave pattern along the entire shoreline, despite the irregular bathymetry. In addition, the alongshore components of infragravity waves refracted by the presence of the nearshore reef were observed to propagate in opposite directions up and down the coast resulting in a local alongshore standing wave pattern. Thus, the presence of highly variable nearshore bathymetry, which commonly occurs along rocky reef coastlines, may produce both cross‐shore and alongshore standing wave patterns.