Browsing by Author "Castelle, Bruno"

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    A new breaking wave height direct estimator from video imagery
    (ELSEVIER SCIENCE BV, 2012) Almar, Rafael; Cienfuegos, Rodrigo; Catalan, Patricio A.; Michallet, Herve; Castelle, Bruno; Bonneton, Philippe; Marieu, Vincent
    Breaker height is a key parameter of nearshore processes and the demand for a continuous remote estimator is pressing. In this paper we present a standalone remote video-based method that estimates wave height at the breakpoint. Individual breaking events are first identified from changes in optical properties and wave height is further derived from the optical signature at the onset of breaking. An extended validation is performed using a dense wave basin dataset. The results show the ability of the method to measure individual breaker heights (9% of mean error, 18% RMS). In addition, the unique combination of in situ and remotely sensed data allows the estimation of two other breaking-related parameters, the height-to-depth ratio and wave front face slope, which show a substantial amount of dispersion. Because nearshore video systems are rapidly spreading over world coasts, this low-cost remote breaker height estimator should encounter large interest in coastal engineering studies. (C) 2011 Elsevier B.V. All rights reserved.
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    SWASH ZONE BASED REFLECTION DURING ENERGETIC WAVE CONDITIONS AT A DISSIPATIVE BEACH: TOWARD A WAVE-BY-WAVE APPROACH
    (2014) Almar, Rafael ; Catalán, Patricio ; Ibaceta, Raimundo; Blenkinsopp, Christopher; Cienfuegos Carrasco, Rodrigo Alberto; Villagrán, Mauricio ; Aguilera, Juan Carlos; Castelle, Bruno
    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 thecut-off 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 andfrequency selection. More investigation is needed to describe the reflection process and its link with shoreface evolution, moving toward a swash-by -swash approach.
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    SWASH-BASED WAVE ENERGY REFLECTION ON NATURAL BEACHES
    (2015) Almar, Rafael; Ibaceta, Raimundo; Blenkinsopp, Christopher; Catalán, Patricio; Cienfuegos Carrasco, Rodrigo Alberto; Trung Viet, Nguyen; Hai Thuan, Duong; Van Uu, Din; Lefebvre, Jean Pierre; Sowah Laryea, Wahab; Laibi, Raoul; Castelle, Bruno; Senechal, Nadia; Anthony, Edward J.
    Can wave reflection be remotely described from swash dynamics and the shoreface slope inversely from reflected waves? In this paper, we revisit the link between swash dynamics and reflection using contrasting field datasets: swell waves on steep and flat beaches and wind waves on an intermediate beach. Reflection ranges from less than 1% to up to 25%. Analyses are conducted from ~10-m depth directional wave spectra measurements, daily beach surveys and video swash measurements. Our results show that swash saturation can be linked to the offshore reflection cut-off frequency (shortest reflected waves) with a strong dependence on swash zone slope, underlining the importance played by swash processes in nearshore dynamics. Moving towards a more process-based approach, an ensemble-average analysis indicates that swash flow asymmetry and skewness are strongly linked to reflection.