Coastal Hazard Assessment · MCU25/0087

                                             17 The Esplanade, Sunshine Beach                              Report




Figure 3-8 Aerial Photograph 2020 (qimagery.information.qld.gov.au)

3.1     Satellite Imagery
Satellite imagery can be used to determine shoreline position and behaviour from 30+ years of
satellite imagery. Satellite platforms include Landsat 5 (1984 - 2013), 7 (1999 - present), 8 (2013 -
present) and Sentinel-2 (2015 - present), with pixel resolution ranging between 10m and 15m and
image capture varying from 5 to 16 days.
Two independent tools have been developed to analyse satellite imagery, which are:

      CoastSat, a Python tool that enables extraction of shoreline position from individual satellite
       images at any coastline worldwide using sub-pixel extraction methods (Vos K., 2019). While
       the horizontal errors for detected shoreline range have been reported to be between 7.3m and
       12.7m Root Mean Square (RMSE) considering individual images, the bias of the data is much
       lower (Vos K., 2019). As such, the temporal resolution of the data means that signals can be
       discerned at seasonal and greater timescales.
      Digital Earth Australia (DEA) is a tool to accurately map the boundary between land and water
       (the ‘waterline’) (Bishop-Taylor. R., 2019). The tool uses the same sub-pixel extraction method
       as CoastSat. However, DEA combines aerials to provide a single, annualised shoreline
       position and is therefore suited to determining long-term trends.
Outputs from both DEA and CoastSat are available online, with key outputs for the coastline adjacent
to the site are provided in Figure 3-9 to Figure 3-10
Figure 3-9 from DEA indicates that the position of the shoreline in the immediate vicinity of the site
has prograded by approximately 0.4m annually (±0.3m at 95% confidence interval) and there has
been minimal progradation (less than ±0.1m/yr) reported at transects nearby to the south. This
indicates that the beach in front of the site is very stable. The shoreline position from the DEA dataset
in Figure 3-10 indicates that the beach has generally been stable from 1988 to the present (only
~35m of shoreline movement).
The CoastSat time series in Figure 3-11 indicates that the shoreline at this location was relatively
stable. Figure 3-11 indicates the shoreline fluctuated by approximately ±30m from the mean shoreline
position annually, some of which may be due to the RSME of the dataset. However, it is likely that
episodic recession and progradation would occur due to seasonal conditions.



                                                                 252662-MN-RP-CO-0001B | 10 November 2025 | Page 15