Swash Zone Based Reflection During Energetic Wave Conditions at a Dissipative Beach: Toward a Wave-by-Wave Approach

Abstract

This paper presents a 11-day experiment conducted at the high-energy dissipative beach of Mataquito, Maule Region, Chile. During the experiment, offshore significant wave height ranged 1-4 m, with persistent long period up to 18 s and oblique incidence. Wave energy reflection value ranged from 1 to 4 %, and results show that it is highly linked to both incoming wave characteristics and swash zone beach slope, and is well correlated to a swash-slope based Iribarren number. The swash acting as a low-pass filter in the reflection mechanism, our results show that the cutoff period is better determined by swash slope rather than incoming wave's period. A new low cost technique for observing high-frequency swash hydro-morphodynamics is introduced and validated using LIDAR measurements. A good agreement is found. Separation of uprush and backswash components using the Radon Transform illustrates the low-frequency filtering effect. These results show the key role played by swash mechanism in the reflection rate and frequency selection. More investigation is needed to describe the reflection process and its link with shoreface evolution, moving toward a swash-by-swash approach.

Optimisation of focused wave group runup on a plane beach

“…Holman and Sallenger, 1985;Hughes and Moseley, 2007) and interpretation of video records (see Holman and Sallenger, 1985; 20 Ruessink et al, 1998;Stockdon et al, 2006, among many others). More recently, lidar has been used for runup measurement in the field (Blenkinsopp et al, 2010;Almeida et al, 2013;Almar et al, 2014;Fiedler et al, 2015) and for measuring free surface elevations in certain largescale experimental facilities (Blenkinsopp et al, 2012). A review of swash zone hydrodynamics, including the effects on beach morphodynamics, is provided by Brocchini and Baldock (2008).…”

Intertidal beach profile estimation from reflected wave measurements

“…The data used in this paper were collected during three experiments undertaken in 2012-2013 at contrasting field sites (Figure 1). A dissipative beach experiment was conducted at Mataquito, Chile, from November 28th to December 14th, 2012 (Figure 1.a, Cienfuegos et al, 2014;Almar et al, 2014a). Mataquito is a medium grain-sized (D50 = 0.2 mm), alongshore uniform, barred beach with a micro-tidal range and a wave climate dominated by swell waves (annual mean significant wave height, Hs ∼ 2.4 m, peak period Tp ∼ 12 s, predominantly from the SW direction).…”

“…Despite this, recent observations have shown that saturation can extend to the infragravity band (Ruggiero and Holman, 2004;Senechal et al, 2011) and infragravity waves can be dissipated through breaking (Van Dongeren et al, 2007;de Bakker et al, 2014;Bertin et al, 2018). Observations at very steep beaches show reflection even in the gravity band (Almar et al, 2014;2018a). In the swash zone, several authors (Huntley et al, 1977;Guza and Thornton, 1982;Ruessink et al, 1998) describe a swash spectra saturation roll-off around f 3 (with f the frequency) based on theoretical analysis and observation.…”