Effects of reef morphology variations on wave processes over fringing reefs.

Highlights • A new set of laboratory data for spectral wave processes over an idealized fringing reef is reported. • Different reef morphologies with/without reef crest, lagoon and reef surface roughness are examined. • Infragravity (IG) waves on reef flat are confirmed to be generated by the breakpoint forcing mechanism. • IG wave resonance on reef flat is identified by a spectral analysis of shoreline wave records. • A Boussinesq model is applied to investigate varying fore-reef slopes, reef-crest widths, lagoon widths, and reef roughness coefficients. Abstract Many low-lying tropical and sub-tropical atolls fringed by coral reefs are susceptible to coastal inundation during extreme wave events. Previous studies have shown that the infragravity (IG) wave is the dominant component of shoreline run-up compared to the sea and swell (SS) wave and the wave-induced setup. To better understand both the SS and IG wave dynamics over a fringing reef with various morphologies, a series of laboratory experiments were conducted in a wave flume based on an idealized fringing reef profile. The shoreline responses of waves to different reef morphologies with/without the reef crest, the lagoon and the reef surface roughness were examined. IG wave resonance on the reef flat was identified by a spectral analysis of the shoreline wave records. Subsequently, a numerical model based on the Boussinesq equations was validated by the experimental data. The model was then applied to investigate the impacts of varying reef morphologic features (fore-reef slope, reef-crest width, lagoon width, and reef roughness coefficient) on the shoreline wave motions. [ABSTRACT FROM AUTHOR]