Linking regional wave conditions to local beach profile change

Abstract

The focus of this study is the beach response to the construction of a coastal defence. The study site is on the frontage of Herne Bay (Kent, UK). The beaches along this segment of coast are predominantly composite, with a shingle upper beach and sandy lower beach, or mixed sand and shingle. The varying beach response updrift and downdrift of, as well as within, the scheme was captured by detailed beach profile surveys covering a period of more than a decade. Canonical correlation analysis has been employed to interpret the beach response in terms of the prevailing wave conditions. The results demonstrate that suitable regression relationships can be found between offshore wave conditions and beach levels at transects throughout the scheme. The regression relationships were also applied to independent wave observations to test whether they could be used to provide useful predictions of beach response. Comparisons between predictions and measurements over a 3 year period are encouraging in this regard. Notably, predictions using ‘offshore’ data provided reasonable predictions of beach response within the scheme without the need for special treatment to account for refraction or diffraction effects. To the east of the scheme the predictions were not as good, indicating that additional factors are important in determining beach profile change there.