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

Abstract

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.

The role of frequency spread on swash dynamics

“…Some authors (Ruessink et al 1998;Guedes et al 2011;Senechal et al 2011) have argued that the use of a local parameter in a complex system (e.g., very different slopes in the swash and surf zones, or the presence of bars) may be misleading, and thus including beach slope does not improve the predictions. Senechal et al (2018) found that the beach morphology in the inner surf zone has a greater influence than the beach face slope, since surf zone morphology modifies the incident wave patterns over a short crossshore distance. Our results agree with this observation.…”

“…Using a numerical model, Guza and Feddersen (2012) found that including the frequency spread offshore f s,0 and directional spread σ θ on run-up parameterizations at the infragravity band reduced the scatter on run-up predictions. The influence of nearshore morphology (such as surf/swash zone interactions) and longshore variability (e.g., the presence of beach cusps) have been identified to also play an important role in swash excursion dynamics (Masselink and Puleo 2006;Bryan and Coco 2010;Senechal et al 2018;Almar et al 2018).…”

“…Other parameters, such as the tidal stage (Guedes et al 2011;Almar et al 2016;Medellín et al 2016) and wave groupness (Baldock and Holmes 1999;Roelvink et al 2018) were found to be relevant especially at the infragravity band. Also, smaller scales related with nearbed dynamics such as grain size (Poate et al 2016), beach variability (Cohn and Ruggiero 2016;Senechal et al 2018), swash-swash interactions, and the role of infiltration and exfiltration have been also addressed (e.g., Masselink and Puleo 2006;Brocchini and Baldock 2008).…”

Etude de la dynamique du runup par modélisation lors d’un épisode de tempête

“…Thème 1 -Hydrodynamique marine et côtière HUGUES et al, 2014, SENECHAL et al, 2018. Thème 1 -Hydrodynamique marine et côtière…”

Experimental Study of Wave Runup Variability on a Dissipative Beach

“…In addition, some recent studies consider runup during storm conditions (Fiedler et al., 2015; Senechal et al., 2011) and extreme runup (García‐Medina et al., 2020; Montoya & Lynett, 2018), or examine the role of infragravity motions (de Bakker et al., 2014; R. A. Holman & Bowen, 1984), and nearshore morphology (Cohn & Ruggiero, 2016; Hughes et al., 2014). A few recent studies (Guedes et al., 2012; Ruggiero et al., 2004; Senechal et al., 2018) further explore the alongshore variability of runup.…”