Visualization of the CALHYCO (Caractérisation de l’ALéa HYdrodynamique COtier) dataset in the ODATIS catalog with location of the Reef Flat and Reef Slope points. Two additional layers were displayed to contextualize these in situ measurement points. These layers correspond (1) to coastal isobaths between -5m and -35 m generated from Hyperspectral (Sprectrhabent OI/Hyscores, metadata sheet) and Litto3D data (2) as well as seabed images over the area “Saint-Gilles Sud: de la Passe de l’Ermitage a Trois Bassin – 2015” from the HYSCORES project.
A new dataset referenced in the ODATIS catalog, supplied by OSU-Réunion and produced as part of the CALHYCO research program, to better understand the coastal defense characteristics of the reef system in the face of waves.
A new entry has been added to the ODATIS catalog, with a dataset supplied by OSU-Réunion and produced as part of the CALHYCO research program: Caractérisation de l’ALéa HYdrodynamique COtier (Characterization of hydrodynamics coastal hazards), with the aim of better understanding the coastal defense characteristics of the reef system in the face of waves.
This dataset contains :
in situ recordings of water level and wave height parameters derived from spectral analysis, on a transect perpendicular to the reef, at the level of the reef slope (RS) and the reef flat (RF) (shown in the figure below),
numerical modelling of water levels and wave heights in the reef using the XBeach model in “surf beat” mode.
The in situ surveys took place in the fringing reef of La Saline-Les-Bains on the west coast of Reunion Island (Indian Ocean), in a microtidal zone seasonally exposed to strong southerly swell trains (in winter) and occasional cyclonic swells. Coral reefs form an effective natural mechanical defense against ocean waves.
Estimating extreme water levels is essential for anticipating coastal vulnerability in the event of surge (rise in water level induced by the effects of low atmospheric pressure and/or winds) and runup (rise in water level at the coast induced by wave action).
The results of the analysis of these measurements, published in an article in JGR Oceans (Bruch W. et al. 2022 DOI: 10.1029/2022JC018570) confirm the effectiveness of the reef’s protection against wave action at the coast, highlighting :
a 95% reduction in incident gravity wave energy
the reef acts as a low-pass filter, transferring energy from incident gravity waves to the lowest frequencies (infragravity)
hydrodynamics in the reef, mainly induced by significant wave heights and modulated by the tide
at low tide, gravity wave dissipation is highest, and set-up in the reef system increases
at high tide, the dissipation of gravity waves is reduced, and more of them reach the beach
in the context of rising sea levels, the protective capacity of the fringing reef at La Saline could be reduced.
95% reduction in incident gravity wave energy
the reef acts as a low-pass filter, transferring energy from incident gravity waves to the lowest frequencies (infragravity)
hydrodynamics in the reef, mainly induced by significant wave heights and modulated by the tide
at low tide, gravity wave dissipation is highest, and set-up in the reef system increases
at high tide, the dissipation of gravity waves is reduced, and more of them reach the beach
in the context of rising sea levels, the protective capacity of this fringing reef at La Saline could diminish.