HOT OFF THE PRESS! DECADAL SHORELINE EROSION AND RECOVERY OF BEACHES IN MODIFIED AND NATURAL ESTUARIES

Figure: A decadal behavioural typology for BEBs. prograding, quasi-stable, retreating, and storm relict. Behaviours are shown with an example BEB from Garigal (Pittwater) or Kamay (Botany Bay) in Sydney.

This international collaboration published the journal Geomorphology includes GRG members Dr Thomas Fellowes and A/Prof Ana Vila-Concejo and former students Ryan Schosberg and Vincent de Staercke, together with international collaborators Dr Shari Gallop from Waikato University (New Zealand), Prof John Largier from University of California Davis (USA). This paper is an outcome of the Partnership Collaboration Award between Sydney University and The University of California Davis and represents a contribution to understanding the controlling mechanisms dictating the decadal shoreline behaviours of sandy beaches in estuaries and bays (BEBs)

Fellowes, T. E., Vila-Concejo, A., Gallop, S. L., Schosberg, R., de Staercke, V., and Largier, J. L., 2021, Decadal shoreline erosion and recovery of beaches in modified and natural estuaries: Geomorphology. https://doi.org/10.1016/j.geomorph.2021.107884

Figure: BEB locations in Garigal (Pittwater) or Kamay (Botany Bay) in Sydney.

In this paper we use 70+ years of aerial and satellite imagery from two estuaries in the Sydney region at Kamay (Botany Bay) and Garigal (Pittwater).  We quantify the erosive effects of powerful storms, measure post-storm recovery rates and present a behavioural typology (see figure).

Main findings from the paper:

  • Decadal beach behaviours are prograding, quasi-stable, retreating or storm relict.
  • Some BEBs recover in less than 15 years (equal or less than storm return timescales), while others never recover and are eroded by subsequent storms.
  • BEB shoreline behaviours are dictated by exposure to swell waves and proximity to the entrance, rivers and flood-tide delta.
  • Anthropogenic interventions (e.g., dredging, groynes) can benefit or be a detriment to estuarine beaches
  • Decadal behaviours will assist coastal management and planning in major cities

Cheers,

Tommy and Ana

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