Response of high-energy, macrotidal beaches to seasonal changes in wave conditions: examples from North Cornwall, UK

Abstract

An experimental wave farm ('Wave Hub') will be installed 20 km off the north coast of Cornwall in 2010. To assess its potential impacts on the nearshore wave climate and beach morphology, an extensive beach monitoring programme has been established. This paper will discuss some preliminary results with specific emphasis on the seasonal morphological response. The North coast of Cornwall is exposed to spring tidal ranges of 5-6 m and a 10% exceedance significant wave height of over 3 m, producing a highly energetic environment. Described as intermediate-dissipative, the beaches exhibit boundary classification features with dominant low tide bar/rip morphology. The sensitivity of such beach types to small variations in seasonal wave conditions can lead to changes in the morphological response of these beach systems which has implications for beach safety during high visitor periods. Seasonal and storm-induced morphological responses are presented for four high-energy, macrotidal beaches. Monthly 3D beach morphology was mapped using differential GPS (DGPS), and supplemented at two sites using daily ARGUS video images. In addition, nearshore wave conditions and tidal data have been combined to provide comprehensive storm and sea-level analysis. Seasonal trends are evident for all sites with clear low water bar morphology dominant in early spring. During summer wave conditions, rip currents are prevalent within the defined bar features prior to onshore migration of bars produces 2D beach profiles with pronounced berm growth.