Infragravity Wave Motions and Runup over Shallow Fringing Reefs

Nwogu, Okey; Demirbilek, Zeki

doi:10.1061/(asce)ww.1943-5460.0000050

Cited by 141 publications

(93 citation statements)

References 36 publications

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“…Laboratory and numerical studies have demonstrated that low frequency wave resonance may occur in nearshore environments that are characterized by certain natural frequencies set by the morphology (such as for a coral reef with a long horizontal bottom) (Nakaza and Hino, 1991;Nwogu and Demirbilek, 2010). In these studies, the promotion of resonance has been suggested to be due to the interaction of these natural frequencies with oscillations generated by the time varying contributions of the wave group forcing.…”

Section: Introductionmentioning

confidence: 99%

Low Frequency Wave Resonance in Fringing Reef Environments

Pomeroy

Dongeren

Lowe

et al. 2012

Int. Conf. Coastal. Eng.

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Low frequency wave resonance has been postulated to enhance damage to coral reef protected coastlines during storm events. This paper uses the numerical model XBeach to examine the dynamics that contribute to resonance that have been previously observed on a fringing reef on Guam during tropical storm Man-Yi (Péquignet et al., 2009). The methods to identify resonance in numerical (or field data) are comprehensively reviewed with three indicators of resonance proposed based upon data obtained at two locations in the model domain: 1. The water surface elevation must be highly coherent, 2. The phase difference must (closely) correspond to 0° or 180°, and 3. Amplification of the signal must be observed between the reef crest and the shoreline. XBeach simulations demonstrated that resonance could be reproduced under 'normal' wave conditions, but only when bottom friction was minimal and hence values that were atypically low for coral reefs. However, under tropical storm Man-Yi conditions, resonance was reproduced with reasonable bottom friction values. A sensitivity analysis demonstrated that, although the frequency associated with resonance was not affected by the choice of bottom friction coefficients, the magnitude of the amplification was significantly affected. Ongoing research is being undertaken to investigate the resonant response for a wider variety of reef morphologies and incident wave forcing conditions.

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Section: Introductionmentioning

confidence: 99%

Low Frequency Wave Resonance in Fringing Reef Environments

Pomeroy

Dongeren

Lowe

et al. 2012

Int. Conf. Coastal. Eng.

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“…Nevertheless, the importance of infragravity waves has been recognised for reefs. For instance, the observation by Nwogu and Demirbilek (2010) that excitation of infragravity waves is possible when a natural frequency is present demonstrated the importance of understanding the interaction of low frequency waves in reef environments. Using laboratory tests of Demirbilek et al (2007) and a Boussinesq-type wave model, they found that low frequency waves could be resonantly amplified at the shoreline with the first reef oscillation mode having a wave length approximately equal to four times the width of the reef flat.…”

Section: Introductionmentioning

confidence: 99%

“…They have examined a number of embedded parameterizations of wave breaking, bottom roughness and nonlinear energy transfer (to the super harmonics), and subsequently have recalibrated these parameterizations to improve the overall model performance. Skotner and Apelt (1999) and Nwogu and Demirbilek (2010) investigated the ability of a Boussinesq-type wave model upon a Guam reef profile. The rate of wave energy dissipation has been determined by tuning several wave breaking parameters (e.g.…”

Section: Introductionmentioning

confidence: 99%

Modelling Wave Transformation Across a Fringing Reef Using Swash

Zijlema

2012

Int. Conf. Coastal. Eng.

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This paper presents the application of the open source non-hydrostatic wave-flow model SWASH to wave propagation over a fringing reef, and the results are discussed and compared with observations obtained from a laboratory experiment subjected to various incident wave conditions. This study focus not only on wave breaking, bottom friction, and wave-induced setup and runup, but also on the generation and propagation of infragravity waves beyond the reef crest. Present simulations demonstrate the overall predictive capabilities of the model for a typical coral reef with steep slopes and extended reef flats.

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“…Van Dongeren et al (2013) used models to show that bottom friction over the reef flat strongly dissipated both SS and IG waves and concluded that nonlinear energy losses were not important. As pointed out by Pomeroy et al (2012), laboratory and model studies of fringing reefs that have suggested the importance of nonlinear energy transfer on the reef flat (Demirbilek, Nwogu, and Ward, 2007;Nwogu and Demirbilek, 2010;Sheremet et al, 2011) were based on idealized smooth substrates with considerably less bed roughness than found at field sites such as Majuro Atoll.…”

Section: (2) Nonlinear Energy Transfer Between Ss and Ig Wavesmentioning

confidence: 99%