Browsing by Author "Bonneton, Philippe"

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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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    On the use of the Radon Transform in studying nearshore wave dynamics
    (2014) Almar, Rafael; Michallet, Herve; Cienfuegos Carrasco, Rodrigo Alberto; Bonneton, Philippe; Tissier, Marion; Ruessink, Gerben
    In the nearshore, describing the complex individual wave dynamics remains a key challenge. In this paper we test the ability of the Radon Transform to produce estimates of individual wave celerities and to separate incoming and outgoing waves conserving the temporal characteristics. The Radon Transform is a projection of a two-dimensional field into polar space. Oblique features such as propagating crests in a spatio-temporal space are identified with density peaks in the polar space. In this paper, the Radon Transform is applied to synthetic test cases including a wide range of beach slopes and wave conditions. The Radon Transform shows good skills at estimating individual celerity and separating incoming and outgoing components with a relative RMS error lower than 10%, even a standing wave node. The accuracy is fairly insensitive to wave characteristics whereas the main limitations rise from the sampling scheme and are the number and density of wave gauges. The distance between gauges should be less than one third of the shortest wavelength, while the set of gauges should cover more than one third of the longest wavelength.
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    Video-Based Detection of Shorelines at Complex Meso-Macro Tidal Beaches
    (2012) Almar, Rafael; Ranasinghe, Roshanka; Senechal, Nadia; Bonneton, Philippe; Roelvink, Dano; Bryan, Karin R.; Marieu, Vincent; Parisot, Jean-Paul
    Remote video imagery is widely used to acquire measurements of intertidal topography by means of shoreline detection, but, up to now, problems of accuracy were still encountered in the challenging case of energetic waves in nonuniform, meso macro tidal environments. Unique, simultaneous, video-based and global positioning system (GPS)-based measurements of shoreline were undertaken at Truc Vert (France), a beach with such characteristics. An innovative video method, referred to herein as the Minimum Shoreline Variability (MSV) method, was developed to cope with highly variable spatiotemporal shoreline properties. The comparison of video-based and GPS-derived shoreline data sets showed that using images averaged over short periods (30 s), rather than the traditionally used 10-min averaged images, significantly improved the accuracy of shoreline determination. A local video-derived, swash-based shoreline correction was also developed to correct for the MSV error, which was found to be linearly correlated to local swash length. By combining shorter time-averaged images and video derived local swash correction factors, the horizontal root mean square error associated with MSV shorelines was reduced to 1.2 m, which is equivalent to errors reported at more uniform, microtidal, and less-energetic beaches.
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    Wave-Breaking Model for Boussinesq-Type Equations Including Roller Effects in the Mass Conservation Equation
    (ASCE-AMER SOC CIVIL ENGINEERS, 2010) Cienfuegos, Rodrigo; Barthelemy, Eric; Bonneton, Philippe
    We investigate the ability of a ID fully nonlinear Boussinesq model including breaking to reproduce surf zone waves in terms of wave height and nonlinear intraphase properties such as asymmetry and skewness. An alternative approach for wave-breaking parameterization including roller effects through diffusive-type terms on both, the mass conservation and momentum equations is developed and validated on regular wave and solitary wave experiments as an attempt to improve wave height and left-right asymmetry estimates. The new approach is able to reproduce wave height decay, and intraphase nonlinear properties within the entire surf zone of spilling breakers without requiring temporal evolution of model parameters.