Grain-size distributions on high-energy sandy beaches and their relation to wave dissipation.

Grain size and sorting represent two key parameters when characterizing sediments or modelling beach morphology and sediment transport. Traditionally, an average value for grain size or sorting is often assumed for the entire area, determined from only a few sediment samples, ignoring any spatial (or temporal) variability in sediment characteristics. This contribution uses a data set of physical surface sediment samples from 53 beach locations around the south-west peninsula of the United Kingdom, in addition to bi-monthly, high spatial resolution (mean 240 samples) digital grain-size surveys from a high-energy, oceanic, sandy beach (Perranporth, North Cornwall). Systematic spatial variations in grain size and sorting were consistently observed in the seaward direction across the intertidal zone of sandy beaches, with grain-sizes coarsening and sorting improving by up to 51·7% and 64·3%, respectively. This variability was deterministically related to the time-averaged, antecedent-adjusted energy dissipated by breaking waves, with the observed maximum grain-size and sorting values correlating with the location of peak wave energy dissipation ( r2 = 0·998, P < 0·01). [ABSTRACT FROM AUTHOR]