Infragravity swash parameterization on beaches: The role of the profile shape and the morphodynamic beach state

Silva, Paula Gomes da; Medina, Raúl; González, M.; Garnier, Roland

doi:10.1016/j.coastaleng.2018.02.002

Cited by 24 publications

(11 citation statements)

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“…Environmental conditions and significant infragravity swash height (S ig ), observed during 13 prominent experiments which underpin much of the understanding of infragravity swash processes on sandy beaches, are presented in Table 1, and their locations and relative exposure are provided in Figure 1. Mean values were obtained from Reference [12] and ranges from Reference [13]. Further information and reference to published works relating to the data in Table 1 can also be found in Reference [10].…”

Section: Background and Literaturementioning

confidence: 99%

Storm Waves at the Shoreline: When and Where Are Infragravity Waves Important?

Billson

Russell

Davidson

2019

JMSE

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Infragravity waves (frequency, f = 0.005–0.05 Hz) are known to dominate hydrodynamic and sediment transport processes close to the shoreline on low-sloping sandy beaches, especially when incident waves are large. However, in storm wave conditions, how their importance varies on different beach types, and with different mixes of swell and wind-waves is largely unknown. Here, a new dataset, comprising shoreline video observations from five contrasting sites (one low-sloping sandy beach, two steep gravel beaches, and two compound/mixed sand and gravel beaches), under storm wave conditions (deep water wave height, H0 up to 6.6 m, and peak period, Tp up to 18.2 s), was used to assess: how the importance and dominance of infragravity waves varies at the shoreline? In this previously unstudied combination of wave and morphological conditions, significant infragravity swash heights (Sig) at the shoreline in excess of 0.5 m were consistently observed on all five contrasting beaches. The largest infragravity swash heights were observed on a steep gravel beach, followed by the low-sloping sandy beach, and lowest on the compound/mixed sites. Due to contrasting short wave breaking and dissipation processes, infragravity frequencies were observed to be most dominant over gravity frequencies on the low-sloping sandy beach, occasionally dominant on the gravel beaches, and rarely dominant on the compound/mixed beaches. Existing empirical predictive relationships were shown to parameterize Sig skillfully on the sand and gravel beaches separately. Deep water wave power was found to accurately predict Sig on both the sand and gravel beaches, demonstrating that, under storm wave conditions, the wave heights and periods are the main drivers of infragravity oscillations at the shoreline, with the beach morphology playing a secondary role. The exception to this was the compound/mixed beach sites where shoreline infragravity energy remained low.

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Section: Background and Literaturementioning

confidence: 99%

Storm Waves at the Shoreline: When and Where Are Infragravity Waves Important?

Billson

Russell

Davidson

2019

JMSE

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“…As previously pointed out by Senechal, Coco, et al (), the choice of the foreshore beach slope defined as β 2 σ might not be suitable as it does not represent the whole cross‐shore profile, particularly in the surf zone. Indeed, recent works (e.g., Gomes da Silva et al, ; Hughes et al, ) indicated that both the profile shape and the morphodynamic beach state should be considered. However, both authors used qualitative parameters (not directly taking into account the beach slope) to represent the 3D large‐scale morphology pattern of the beach: while Hughes et al () used the beach classification proposed by Wright et al (), Gomes da Silva et al () proposed to use the nondimensional fall velocity parameter.…”

Section: Discussionmentioning

confidence: 99%

“…Indeed, recent works (e.g., Gomes da Silva et al, ; Hughes et al, ) indicated that both the profile shape and the morphodynamic beach state should be considered. However, both authors used qualitative parameters (not directly taking into account the beach slope) to represent the 3D large‐scale morphology pattern of the beach: while Hughes et al () used the beach classification proposed by Wright et al (), Gomes da Silva et al () proposed to use the nondimensional fall velocity parameter. In this study, an additional difficulty is related to the presence of the sandwave creating a much milder and homogenous surf zone slope in the area that also likely influences the runup.…”

Section: Discussionmentioning

confidence: 99%

“…Senechal, Coco, et al () pointed out that the Iribarren number, initially developed for laboratory plane beaches, can be misleading as its application to field studies requires a single beach slope value to characterize the whole cross‐shore profile. In most previous works (e.g., Gomes da Silva et al, ; Guedes et al, , ; Ruggiero et al, ; Senechal, Coco, et al, ; Stockdon et al, ), the beach slope β was defined as the β 2 σ , which is the linear slope within the region between ± two standard deviations from the mean runup elevation. However, Senechal, Coco, et al () pointed out that in their study, the steep slopes characterizing the swash zone were in contrast with the mildly sloping surf zone; as a result, the swash zone experienced nearly reflective conditions while the surf zone was in a dissipative state.…”

Section: Introductionmentioning

confidence: 99%

“…Passarella et al (), applying the machine learning technique from genetic programming on a large data set including a wide range of conditions from reflective to dissipative, found that the beach slope is a relevant parameter when predicting the infragravity component. In contrast, Gomes da Silva et al () suggested using the horizontal cross‐shore component of the infragravity swash instead of the associated vertical component and found it to be related to the foreshore slope (defined as β 2 σ ) and the morphodynamic beach state through the nondimensional fall velocity parameter.…”

Section: Introductionmentioning

confidence: 99%

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Field Observations of Alongshore Runup Variability Under Dissipative Conditions in the Presence of a Shoreline Sandwave

et al. 2018

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Video measurements of runup were collected at low tide along several profiles covering an alongshore distance of 500 m. The morphology displayed a complex shape with a shoreline sandwave in the lower beach face of about 250 m long mirrored in the inner sandbar. Wave conditions were stationary and moderate (offshore height of 2 m and peak period of nearly 13 s) but yet dissipative. Runup energy was dominated by infragravity frequencies. Alongshore variations in runup (by a factor up to 3) observed both in the incident and infragravity bands were much higher than reported previously (e.g., Guedes et al., 2012Guedes et al., , https://doi.org/10.1016Guedes et al., /j.csr.2012Ruggiero et al., 2004, https://doi.org/10.1029/2003JC002160) while the alongshore variations in other environmental parameters (e.g., foreshore beach slope) appear to be much lower. Our data suggest that the beach morphology in the inner surf zone plays a crucial role by inducing rapid and significant modification in the incident wave pattern and the alongshore coherence length scales were consistent with the typical alongshore length scale of the morphology.Plain Language Summary The topic of this work is to present new field data focusing an alongshore variation of the runup. The runup is the time-varying position of the water's edge on the foreshore of the beach. This parameter is crucial in better forecasting coastal hazards (e.g., coastal flooding and erosion) and coastal structure defense design.

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