Low Frequency Wave Resonance in Fringing Reef Environments

Pomeroy, Andrew; Dongeren, Ap van; Lowe, Ryan J.; Vries, Jaap van Thiel de; Roelvink, J.A.

doi:10.9753/icce.v33.currents.25

Cited by 11 publications

(24 citation statements)

References 30 publications

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“…It would appear that in Puerto Morelos the width of the reeflagoon has a greater influence on the resonant periods than the water depth (W = 460 m at P0; see Table 1). This is in agreement with results presented by Pomeroy (2011). …”

Section: Infragravity Wave Energysupporting

confidence: 83%

Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon

Torres-Freyermuth¹,

Mariño‐Tapia

Coronado

et al. 2012

Nat. Hazards Earth Syst. Sci.

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Abstract. Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon are investigated by means of a phase-resolving non-hydrostatic wave model (SWASH). This model solves the nonlinear shallow water equations including non-hydrostatic pressure. The one-dimensional version of the model is implemented in order to investigate wave transformation in fringing reefs. Firstly, the numerical model is validated with (i) laboratory experiments conducted on a physical model (Demirbilek et al., 2007) and (ii) field observations (Coronado et al., 2007). Numerical results show good agreement with both experimental and field data. The comparison against the physical model results, for energetic wave conditions, indicates that high-and low-frequency wave transformation is well reproduced. Moreover, extreme water-level conditions measured during the passage of Hurricane Ivan in Puerto Morelos are also estimated by the numerical tool. Subsequently, the model is implemented at different along-reef locations in Puerto Morelos. Extreme water levels, wave-induced setup, and infragravity wave energy are estimated inside the reef lagoon for different storm wave conditions (H s > 2 m). The numerical results revealed a strong correlation between the offshore sea-swell wave energy and the setup. In contrast, infragravity waves are shown to be the result of a more complex pattern which heavily relies on the reef geometry. Indeed, the southern end of the reef lagoon provides evidence of resonance excitation, suggesting that the reef barrier may act as either a natural flood protection morphological feature, or as an inundation hazard enhancer depending on the incident wave conditions.

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Section: Infragravity Wave Energysupporting

confidence: 83%

Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon

Torres-Freyermuth¹,

Mariño‐Tapia

Coronado

et al. 2012

Nat. Hazards Earth Syst. Sci.

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“…This resonant forcing and VLF patterns over the Ipan reef were found to be caused by the modulation of breaking swell waves at the reef crest [ Péquignet et al ., ]. A subsequent modeling study based on the Ipan observations found that the forcing of resonant modes over this reef was dependent on not only the increase in water levels due to the storm event, but also the frictional characteristics of the reef flat; dissipation due to bottom friction counteracts the excitation of resonant frequencies by dampening the amplification peaks at the shoreline [ A. W. M. Pomeroy et al ., ]. Thus, for a given reef geometry and water depth, one would expect smoother, lower relief reefs, such as Roi‐Namur, to be subject to greater shoreline amplification due to resonance modes.…”

Section: Discussionmentioning

confidence: 99%

Observations of wave transformation over a fringing coral reef and the importance of low‐frequency waves and offshore water levels to runup, overwash, and coastal flooding

2016

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Many low‐lying tropical islands are susceptible to sea level rise and often subjected to overwash and flooding during large wave events. To quantify wave dynamics and wave‐driven water levels on fringing coral reefs, a 5 month deployment of wave gauges and a current meter was conducted across two shore‐normal transects on Roi‐Namur Island in the Republic of the Marshall Islands. These observations captured two large wave events that had waves with maximum heights greater than 6 m with peak periods of 16 s over the fore reef. The larger event coincided with a peak spring tide, leading to energetic, highly skewed infragravity (0.04–0.004 Hz) and very low frequency (0.004–0.001 Hz) waves at the shoreline, which reached heights of 1.0 and 0.7 m, respectively. Water surface elevations, combined with wave runup, reached 3.7 m above the reef bed at the innermost reef flat adjacent to the toe of the beach, resulting in flooding of inland areas. This overwash occurred during a 3 h time window that coincided with high tide and maximum low‐frequency reef flat wave heights. The relatively low‐relief characteristics of this narrow reef flat may further drive shoreline amplification of low‐frequency waves due to resonance modes. These results (1) demonstrate how the coupling of high offshore water levels with low‐frequency reef flat wave energetics can lead to large impacts along fringing reef‐lined shorelines, such as island overwash, and (2) lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of these extreme events, negatively impacting coastal resources and infrastructure.

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“…In this region, low-frequency waves (i.e., infragravity waves with periods 25-250 s) are generated by the breaking of incident high-frequency waves (Péquignet et al, 2014;Pomeroy et al, 2012a). In some cases low-frequency wave motions with periods even larger than the infragravity band (i.e., periods exceeding 250 s) can also be generated at the natural (seiching) frequency of coral reef flats, which may also be resonantly forced by incident wave groups (Péquignet et al, 2009;Pomeroy et al, 2012b). This disparity between high and low-frequency waves often results in a bimodal spectrum of wave conditions on coral reef flats and lagoons, where wave energy is partitioned between distinct high-frequency (sea-swell) and low-frequency (infragravity) wave bands (Pomeroy et al, 2012a;Van Dongeren et al, 2013).…”

Section: Introductionmentioning

confidence: 98%

Spectral wave-driven sediment transport across a fringing reef

Pomeroy

Lowe

Dongeren

et al. 2015

Coastal Engineering

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a b s t r a c tA laboratory experiment was conducted to investigate the dynamics of cross-shore sediment transport across a fringing coral reef. The aim was to quantify how a highly bimodal spectrum of high-frequency (sea-swell) and low-frequency (infragravity and seiching) waves that is typically present on coral reef flats, influences the various sediment transport mechanisms. The experiments were conducted in a 55 m wave flume, using a 1:15 scale fringing reef model that had a 1:5 forereef slope, a 14 m long reef flat, and a 1:12 sloping beach. The initial 7 m of reef flat had a fixed bed, whereas the back 7 m of the reef and the beach had a moveable sandy bed. Four seven-hour irregular wave cases were conducted both with and without bottom roughness elements (schematically representing bottom friction by coral roughness), as well as for both low and high still water levels. We observed that the wave energy on the reef flat was partitioned between two primary frequency bands (high and low), and the proportion of energy within each band varied substantially across the reef flat, with the lowfrequency waves becoming increasingly important near the shore. The offshore transport of suspended sediment by the Eulerian mean flow was the dominant transport mechanism near the reef crest, but a wide region of onshore transport prevailed on the reef flat where low-frequency waves were very important to the overall transport. Ripples developed over the movable bed and their properties were consistent with the local highfrequency wave orbital excursion lengths despite substantial low-frequency wave motions also present on the reef flat. This study demonstrated that while a proportion of the sediment was transported by bedload and mean flow, the greatest contributions to cross-shore transport were due to the skewness and asymmetry of the high and low-frequency waves.

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Low Frequency Wave Resonance in Fringing Reef Environments

Cited by 11 publications

References 30 publications

Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon

Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon

Observations of wave transformation over a fringing coral reef and the importance of low‐frequency waves and offshore water levels to runup, overwash, and coastal flooding

Spectral wave-driven sediment transport across a fringing reef

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