Slapton barrier beach case study, UK

Slapton Barrier Beach Coastal Processes Study Coastal Engineering Research Group University of Plymouth, UK

Summary: In 2003, the Slapton Line Partnership (http://www.slaptonlinepartnership.co.uk/) commissioned a major study to make a comprehensive evaluation of the issues relating to coastal processes at Slapton Sands. The primary purpose of the study was to determine an appropriate future shoreline management response. The study was carried out by Scott Wilson (http://www.scottwilson.com/Default.aspx?page=8998) in collaboration with the University of Plymouth. The contribution of the Coastal Engineering Research group (http://www.research.plymouth.ac.uk/cerg/default.shtml) was to carry out a geomorphological assessment, analysis of coastal processes and analysis of shoreline response and sea level rise. Details: Slapton Sands is recognised for its nature conservation and landscape importance. The shingle ridge and Slapton Ley is designated as a Site of Special Scientific Interest (SSSI), as a National Nature Reserve (NNR) and as a Geological Conservation Review site. During a series of storms in the winter of 2000/01, significant damage occurred to the barrier beach at Slapton, where a 250 m section of the road was severely damaged.

The study involved analysis of coastal processes on both geomorphological and contemporary timescales, numerical modelling of wave transformations and shoreline evolution, breach modelling and cross-shore profile modelling. It was found that the key beach processes affecting Slapton Sands are: short term storm impacts, medium term longshore transport gradients; long term sea-level rise causing rollback of the barrier beach.

The overall assessment of the January 2001 event is that it was caused by a combination of beach line recession due to differential longshore transport rates in the preceding autumn and the occurrence of a 1 in 25 year storm event lasting four days, which further cut back the profile, with the beach crest reaching road level.

The risk of a breach of the shingle bank will remain low over the next 30 to 50 years. Future sea-level rise and increased storminess will increase the rate of erosion and the risk of a major recession event. With no intervention measures, it is anticipated that the barrier beach will eventually be breached forming tidal inlets.