Seasonal response of a composite beach in relation to wave climate

Abstract

Most studies regarding coastal morphodynamic have focused on sandy beaches or beaches with a single type of sediment. Wave climate has been described as one of the main factors behind the morphological changes, although this interaction is not fully understood on composite beaches. The aim of this work is to present new insights into the seasonal variability of a composite beach called San Felipe (Gran Canaria, Spain). Statistically significant correlations were obtained between different measured morphological variables, morphodynamic parameters and the wave climate. The run-up and Iribarren number were found to be good indicators of the morphological response of a composite beach. The morphological seasonal dynamics of this composite beach enabled the definition of two morphodynamic beach states which correspond to summer and winter situations. The summer state is characterized by a profile with two different sedimentological and morphological sections: an upper part dominated by pebbles forming two berms, and a lower sandy section with a gentle slope. Spilling low-energy waves dominate and the beach follows a dissipative-intermediate pattern. The winter state is defined by a reflective-intermediate behaviour of the beach, which is narrower and steeper. Two morphological features were identified: a single storm berm and cusps along the foreshore. Plunging breakers and high-energy waves dominate during winter. Based on the results obtained in this study, a new classification of composite beaches is proposed.