Shingle beach response to swell wave action

Abstract

Coastal erosion has long been associated with longshore transport or litteral drift generated by storm waves. At the same time, swell waves have been perceived to have benefiting effects in preserving our beaches. This may not always be the case. Field observations along the southern coastline of England have shown that shingle beaches can suffer large losses of beach material under the action of swell waves. A model study has been carried out to examine the response of a shingle beach to swells of various periods and heights. It will be shown that the onshore or offshore movement of beach material is strongly associated with both the wave period and height. Under certain conditions, swell waves can cause severe damage to the beach by removing the beach crest material and transporting it offshore into deep water where the material becomes irretrievable. The findings of this study suggest that while swells of small amplitude help to maintain the beach material, swell of sufficient heights can cause both short and long term losses of beach material, resulting erosions of beaches. This has significant implications in establishing good coastal protection schemes where needed.