Morphological changes in a cuspate sandy beach under persistent high-energy swells: Reñaca Beach (Chile).

The present work proposes a morphological evolution model for sandy cuspate beaches, which depends on two parameters, swash excursion (S) and offshore wave steepness (H 0 / L 0). The model was derived from observations of morphology and wave climate at Reñaca Beach in central Chile, comprising in-situ instrumentation, topographic surveys, wave modeling, and optical imagery. It was found that wave steepness alone was unable to explain the morphological changes observed on the beach. Rather, results indicate that swash excursion is better to distinguish between erosive and accretionary events, with swash excursion exceeding 29.5 m for more than 12 h being indicative of erosive events. While morphological changes are led by S , wave steepness correlates with the erosive potential of waves, especially when H 0 / L 0 is greater than 0.017. Although derived for a specific beach under a limited range of conditions, this work adds to the understanding of the dynamic behavior of beaches exposed to persistent high-energy swells. Unlabelled Image • Horizontal swash excursion is determinant in controlling erosion of a cuspate beach under persistent high-energy swells. • All erosion events occur when swash excursion exceeds 29.5 m for over 12 h. • Erosion events are driven by swash excursion, with wave steepness enhancing erosive potential. • The magnitude of accretion and erosion is conditioned by the antecedent state. [ABSTRACT FROM AUTHOR]