Beach response to a sequence of extreme storms

Abstract

A sequence of daily beach surveys acquired over one month covering an area larger than 100,000 m2, was analyzed to study morphological changes resulting from a cluster of storms. The beach response was highly variable in both the cross- and alongshore. A cumulative storm effect was not observed, despite one storm being characterized by a 10-year return period that had significant wave height (Hs) of 8.1 m and a peak wave period (Tp) of 17 s. Instead, storms that can potentially cause significant erosion in terms of Hs had a limited effect on the morphology because the large wave height was coupled to either neap tides, normally-incident short-waves (f > 0.04 Hz), or low levels of infragravity (0.004 < f < 0.04 Hz) energy. Multiple linear regression analysis shows that volumetric changes in the upper part of the beachface are explained by offshore wave characteristics (period, height and direction), tidal range or by infragravity energy in the inner surf zone (assessed using pressure and velocity measurements). The results indicate that it is not possible to scale-up single-storm erosion studies into predictions of cluster-storm erosion.