Barrier island geomorphology, hydrodynamic modelling, and historical shoreline changes: an example from South Uist and Benbecula, Scottish Outer Hebrides

Alastair G. Dawson, Cristina Gomez, William Ritchie, Crispian Batstone, Mark Lawless, John S. Rowan, Sue Dawson, Jason McIlveny, Richard Bates, David Muir

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A quantitative reconstruction is provided of the evolution of Gualan Island, a barrier island located between South Uist and Benbecula in the Scottish Outer Hebrides using historical maps, aerial photographs and LiDAR (Light Detection and Ranging) data. Geomorphological changes over the last ca. 200 years are described together with quantitative changes in the dimension of the barrier island as well as rates of shoreline retreat. A series of digital terrain models (DTMs) provided the boundary conditions for a 2-D ocean circulation tide-surge model simulating water level and wave conditions associated with a highly destructive storm that took place during January 2005. During this storm event, the central part of the barrier island was overtopped by waves. Validating the hydrodynamic model against eye-witness and field evidence obtained after the 2005 storm allowed simulation of a range of potential future breaching scenarios. Thus with the same storm conditions a large barrier breach 500 m wide would result in wave heights rising by 0.8-0.9 m on hitherto sheltered shorelines.
Original languageEnglish
Pages (from-to)1462-1476
Number of pages15
JournalJournal of Coastal Research
Issue number6
Early online date13 Apr 2012
Publication statusPublished - 1 Nov 2012



  • Barrier island
  • Gualan Island
  • Scottish Outer Hebrides
  • geomorphological reconstruction
  • January 2005 storm in Atlantic Scotland
  • digital terrain modelling
  • hydrodynamic models

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