Post-wildfire coastal dunefield response using photogrammetry and satellite indices

Fire has been suggested to be an initiation mechanism of landscape instability and coastal dune transgression, but modern evidence showing a shift to a transgressive dune phase is lacking. Following the largest wildfire in historical records on Kangaroo Island, South Australia, bimonthly uncrewed aerial vehicle (UAV) surveys were conducted on three coastal dune sites to study their post-fire responses. The three sites studied here represent the landscape diversity of the temperate dunes of Kangaroo Island with both active coastal and inland relict stabilised dune fields studied. UAV surveys were used to reconstruct landscapes with structure from motion (SfM) photogrammetry and compared over time to illustrate significant changes in the landscape. The geomorphic and vegetation changes are compared in net and intra-survey comparisons to illustrate the post-fire dunefield response and trends towards stabilisation. Because of a lack of reliable baseline pre-fire data, satellite geomedians are used to compute spectral indices to show the trajectory of ground cover in the study sites in the years preceding and following the fire. Satellite indices are used to separate 3D changes according to ground cover types and show their differing post-fire responses. Local and regional wind, temperature and rainfall records are presented to provide weather patterns of the years preceding and following the fire, illustrating the wet and mild post-fire weather. The overall results indicate no significant landscape instability across the studied sites and that the ground cover of vegetation is nearing pre-fire baselines, showing that a severe fire has not caused a transgressive dunefield to develop.