Hot off the press! Morphodynamic controls for growth and evolution of a rubble coral island

Please join me in congratulating the postdoctoral researcher Lara Talavera and the team on the publication of a new paper in the journal Remote Sensing. This work started when she was hosted by the GRG for three months back in 2019, when she was affiliated in the Earth Sciences Department of the University of Cádiz (Spain). The paper represents another wonderful contribution to understanding the controlling mechanisms dictating the evolution of One Tree Island (Southern Great Barrier Reef), which are transferable to other coral rubble islands of the world.

Talavera, L.; Vila-Concejo, A.; Webster, J.M.; Smith, C.; Duce, S.; Fellowes, T.E.; Salles, T.; Harris, D.; Hill, J.; Figueira, W.; Hacker, J. Morphodynamic Controls for Growth and Evolution of a Rubble Coral Island. Remote Sens. 202113, 1582.

We analysed the geomorphic changes in OTI by using different remotely-sensed data from a variety of methods (e.g., satellite imagery, RTK-DGPS, kites, LiDAR, and drones) and across varying timescales (decadal and annual) coupled with wave data extracted from satellite altimetry and cyclone activity.

Findings from the paper:

  • One Tree Island is a morphologically dynamic island that has been growing since its initial formation. It grew by 7% in a 41-year period (from 1978 to 2019) while experiencing substantial net planform changes.
  • Gross planform adjustments in rubble islands like One Tree are partly governed by the number and intensity of cyclones which in turn are influenced by the positive and negative ENSO phases as well as by their proximity and relative position to the island.
  • Rubble spits play important roles in island growth. Our study identified two mechanisms: (1) rubble spit welding to the island followed by wave-driven longshore transport to feed other parts of the island; (2) in cases where one end of the rubble spit was connected to the island, there was some evidence of overtopping processes contributing to island growth in elevation. The contribution of overtopping to the evolution of rubble islands requires further research.
  • Deciphering the future trajectory of rubble islands under a climate change scenario becomes a challenging task unless efforts are joined towards a complete understanding of the individual impacts of the controls involved on island change and evolution, which in turn will require more frequent quantitative island observations and monitoring. It is only building on that basis that we could better comprehend the impacts of those island controls combined, and the responses, in turn, may vary from island to island according to their own geological and ecological characteristics.


Jody and Ana


Figure. Planform geomorphic changes and evolution of (a) the island perimeter/shape (1964–2019) and (b) island vegetation line/core (1978–2019), where the black arrows indicate the direction of the planform changes. (c) Net changes in the island perimeter between 1964 and 2019 (grey hatch and brown outer line), and net changes in the vegetated core between 1978 and 2019 (green and brown inner lines), and (d) OTI vegetated core areal changes (in m2 and in % change, where green represents the measured areas (Table 4), and blue and red represent gross increase and decrease in size, respectively). Dotted lines represent the possible location of previous shorelines inferred from the high-resolution LiDAR captured in 2018.


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