Figure 1 . Challenges of estimating the steepness of the intertidal zone in a dynamic coastal environment where the beach face is constantly fluctuating landwards/seawards due to erosion/accretion processes. Red dots indicate long-term satellite-derived shoreline measurements (x coordinate) sampled at various tidal elevations (y coordinate). a) Hypothetical example of a static beach profile where the cross-shore variations in the water line are entirely due to the rise and fall of the tide and therefore the intertidal beach profile can be accurately reconstructed. b) Real-world example of a surveyed profile at Narrabeen Beach (Australia) where the continuous erosion and accretion of the beach results in scattered observations from which it is not possible to reconstruct the intertidal beach profile.
2 Materials and Methods