SWASH-BASED WAVE ENERGY REFLECTION ON NATURAL BEACHES

Abstract

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.