Inter-annual morphological evolution and volume changes of a meso- to macrotidal beach exhibiting multiple intertidal bars (MITB)

Melanie Biausque, Edoardo Grottoli, DWT Jackson, Andrew Cooper

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Although morphologically persistent in the long term, Multiple Intertidal Bar Systems (MITBs) display short-term, especially seasonal, morphodynamic behaviour. Analysis of high-density, monthly DGPS surveys conducted at Murlough and Ballykinler beaches, inter- and supratidal sediment volumes and hydrodynamic forcing (wave conditions and water levels), demonstrates a link between strong seasonality in wave climate and MITB beach behaviour. Summer, low-energy conditions limit cross-shore sediment exchange during which MITB beach morphology tends to stabilise throughout the season. With the onset of high-energy winter conditions cross-shore sediment exchanges occur between inter- and supratidal areas. Sediment transport is then enhanced during storm conditions that are coincident with spring tides, leading to high total water levels (TWL). Ultimately the storm sequencing, (frequency, magnitude and inter-storm interval), is the key parameter driving the beach morphological response. Major erosional patterns occur when the most energetic event, combined with spring high tide, occurs at the beginning of the winter season. Subsequent, less energetic storms then promote bar recovery until another extreme event occurs.

Seasonality is also evident in alongshore dynamics. Cross-shore drainage channels that dissect the intertidal bars migrate alongshore, driving alongshore sediment transport and MITB longshore migration patterns. In summer migration of drainage channels is limited, whereas the winter high-energy forcing enhances channel migration rates and resulting sediment transport. Differences in dynamics between the two study sites are attributed to differences in local geology, beach morphology and sediment size, but in both locations, drainage channels are in fine migrating toward the inlet and associated ebb delta that divides the bay. Subsequent transport vectors are unknown, but the observations highlight the primary role of the inlet in the sediment circulation dynamics in the system as a whole.
Original languageEnglish
Article number 108728
Early online date18 May 2023
Publication statusPublished online - 18 May 2023

Bibliographical note

Funding Information:
This study was conducted within the MarPAMM project supported by the EU's INTERREG VA Programme, thanks to the Special EU Programmes Body, with match funding from the Department of Agriculture, Environment and Rural Affairs in Northern Ireland and the Department of Housing, Planning and Local Government in Ireland ( ).

Publisher Copyright:
© 2023


  • Beach morphodynamics
  • sandy coasts
  • intertidal bars
  • sediment transport
  • Cross-shore and alongshore dynamics
  • Bar-trough channels
  • Sandy coasts
  • Intertidal bars
  • Sediment transport


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