Shoreline change on a tropical island beach, Seven Mile Beach, Grand Cayman: the influence of beachrock and shore protection structures

Wendy Johnston, Andrew Cooper, Jeremy Olynik

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5 Citations (Scopus)
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Abstract

Contemporary and near-future shoreline change is widely regarded as an issue on small tropical islands. While it is widely anticipated that sea-level rise will precipitate shoreline recession on tropical islands, studies to date record both accretion and recession at historical timescales. This study of Seven Mile Beach, Grand Cayman presents a case study of historical shoreline change in which the local geomorphic setting is shown to be an important influence on shoreline behaviour. Consistent with its leeside setting, historic shoreline analysis (1958–2019) reveals erosion on the margins and accretion in the central part of the headland-embayment beach where no beachrock is present. The beach comprises five discrete, but interlinked subcells delineated by low headlands of exposed beachrock. These headlands have emerged through shoreline recession post-1971 but once exposed have become loci of persistent erosion, suggesting a positive feedback between beachrock and waves. A Category 5 Hurricane generated waves directly opposed to long-term modes and throughout the beach, long-term patterns of shoreline change were temporarily reversed, however, the historic pattern of shoreline change was restored within 2 years. The contemporary patterns of erosion and cell development suggest a reduction in sediment supply leading to cannibalization of relict beachridges on the margins of the embayment and emergence of formerly buried beachrock. The effects of coastal structures and erosion abatement measures were assessed and recommendations for coastal management, including development setback lines are presented.
Original languageEnglish
Article number107006
Pages (from-to)1-18
Number of pages18
JournalMarine Geology
Volume457
Early online date9 Feb 2023
DOIs
Publication statusPublished (in print/issue) - 1 Mar 2023

Bibliographical note

Funding Information:
Thank you to the Cayman Islands Department of Lands & Survey and Department of Environment. This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.

Publisher Copyright:
© 2023 The Authors

Keywords

  • Beach morpholgy
  • Digital shoreline Analysis
  • Beachrock
  • Caribbean
  • Shoreline movement
  • Coast
  • Digital shoreline Analysis System
  • Beach morphology

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