The Coastal Geomorphology of North Cornwall: St. Ives Head to Trevose Head

Abstract

On the 6th December 2007 the UK Secretary of State for Environment, Food and Rural Affairs permitted the South West of England Regional Development Agency (SWRDA) to provide the necessary infrastructure to support and encourage developers of wave energy converters (WECs) to trial clusters of renewable energy devices in a so-called ‘wave-farm’ called the ‘Wave Hub’ [SWRDA, 2008]. The proposed location is 20km northwest of St. Ives in north Cornwall, in 50-60m water depth [South West of England Regional Development Agency, 2006]. It will be able to generate 20 megawatts of electricity over a deployment area of 4 × 2 kilometres (see Figures 1.1 and 1.2), feeding to an electricity substation located behind the dunes at Hayle [South West of England Regional Development Agency, 2006]. It represents the world’s first large scale wave farm, supporting up to 30 wave energy devices, expected to be operational in 2009 [SWRDA, 2008]. A modelling study carried out by South West of England Regional Development Agency [2006] suggested that the Wave Hub would cause between 3 and 5% reduction to wave height between Gwithian and Newquay, as well as minor changes to surface tidal currents and offshore bed elevations. However, due to the inherent uncertainty behind such coastal modelling approaches in this hydrodynamic data-poor region, the WHISSP (Wave Hub Impact on Seabed and Shoreline Processes) project has been commissioned at the University of Plymouth to model and monitor the impact on the sea bed and shoreline of devices deployed in the Wave Hub project [UoP, 2008]. One of the key areas for concern regarding Wave Hub is an estimated wave height attenuation and tidal current modification in the lee of the Hub, and the associated impact on sedimentation, beach topography and beach state. A particular focus of WHISSP will therefore be on those popular recreational beaches in the hub’s shadow. While the extend of the shadow cannot be known until the WEC devices are installed, the maximum likely extend is the stretch of north Cornwall between St. Ives and Trevose (see Figure 1.2), which is therefore the subject of this manuscript. This report details fifty-three individual beaches and coves in the study area, which have been selected based on their area (≥ 1000 m2). For each, a brief description of their character, physiography and physical attributes is given, based on the analysis of maps and secondary literature. The major beaches in the area, some fifteen in total, have also been sampled for their sediment and the results of particle size and carbonate analyses are given. Where available, panoramic photos, beach profiles and digital elevation models are presented, based on recent surveys. Finally, these fifteen major beaches have been classified under a morphodynamic classification scheme.