The Effects of Tidal Translation on Wave and Current Dynamics on a Barred Macrotidal Beach, Northern France

Abstract

Barred macrotidal beaches are affected by continuous horizontal displacements of different hydrodynamic zones associated with wave transformation (shoaling, breaker and surf zones) due to significant tide-induced water level changes. A series of wave and current meters, complemented by a video imagery system, were deployed on a barred beach of northern France during a 6-day experiment in order to characterize the spatial and temporal variability of wave-induced processes across the beach. Wave and current spectral analyses and analyses of cross-shore current direction and asymmetry resulted in the identification of distinct hydrodynamic processes, including the development of infragravity waves and offshore-directed flows in the breaker and surf zones. Our results revealed a high spatial variability in the hydrodynamic processes across the beach, related to the bar-trough topography, as well as significant variations in the directions and intensity of cross-shore currents at fixed locations due to the horizontal translation of the different hydrodynamic zones resulting from continuous changes in water level due to tides.

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“…Tides are periodical metric fluctuations of the sea level mainly produced by the gravitational force of the moon and the sun, with daily vertical sea level variations ranging between low/negligible values (microtidal coasts, average range < 2 m), intermediate values (mesotidal, 2<range<4 m) and high to very high ranges (macrotidal coasts, range> 4 m). In meso and macro tidal regimes tides translate waves and associated currents up and down the nearshore zone, hence modelling their effects (Dey and Shukla, 2019;Héquette et al, 2021). Tidal currents under macrotidal regimes are strong enough to control beach morphodynamics (Bennett et al, 2019), especially around capes or inside straits, where bottom morphology is the main factor controlling the speed and lateral variations in energy flux (Sánchez Román et al, 2012).…”

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“…Tides are periodical metric fluctuations of the sea level mainly produced by the gravitational force of the moon and the sun, with daily vertical sea level variations ranging between low/negligible values (microtidal coasts, average range < 2 m), intermediate values (mesotidal, 2<range<4 m) and high to very high ranges (macrotidal coasts, range> 4 m). In meso and macro tidal regimes tides translate waves and associated currents up and down the nearshore zone, hence modelling their effects (Dey and Shukla, 2019;Héquette et al, 2021). Tidal currents under macrotidal regimes are strong enough to control beach morphodynamics (Bennett et al, 2019), especially around capes or inside straits, where bottom morphology is the main factor controlling the speed and lateral variations in energy flux (Sánchez Román et al, 2012).…”