Morphological response of an embayed beach to swell-driven storminess cycles over an 8-year period

Abstract

This study contributes to the understanding of the extent at which antecedent hydrodynamic and morphological conditions affect post-storm morphology in response to individual storms and storm clusters. Nearshore wave measurements and concurrent fortnightly to monthly topographies from 2012 to 2020 were used to determine the morphological response of a swell-dominated beach in the Pacific coast of NW Baja California to different storm types. The beach attained an almost nil volumetric balance over the eight-year period, but significant variations existed related to storm incidence. Higher storminess occurred during El Niño years and lower or absence of storminess during years of La Niña phase. The integral wave characteristics of the analyzed swell-dominated storms did not conclusively explain subaerial volume variations. Dissipative morphodynamic conditions prevailed during the analyzed storm events (Ω of 6 to 8) and the wave steepness presented relatively small variations (0.006 to 0.015). The beach quickly reached a storm equilibrium state, preventing subsequent adjustment when further storms in the sequence acted. Moreover, consecutive storms to highly-erosive events caused subaerial beach accretion when low pre-storm volumes (< 50 m3m−1 than average) and mild lower intertidal slopes (tanβ > 0.03) existed. It is concluded that the erosive potential of the swell-driven storms primarily depended on the antecedent sediment availability and near-shoreline slope.