Coastal Hazard Assessment · MCU25/0087

                                            17 The Esplanade, Sunshine Beach                              Report




                                 Figure 5-12 Dune heights and beach profile

5.3.6   Sediment size
BMT (2018) and M&N both adopted a median sediment grain size (D50) of 0.22mm.
5.3.7   Storm Tide
BMT (2018) stated that a 100 year ARI design storm tide level (inclusive of wave setup) for Sunshine
Beach of 2.61m AHD was adopted based on a storm tide assessment by Aurecon (2013). However,
when reviewing the assessment summary provided it appears that a design storm tide level of 2.20m
AHD was used by BMT (2018) for assessment of the short-term erosion component of the erosion
prone area. There is no clear explanation provided by BMT (2018) for the differ storm tide levels
described in their report.
(Vellinga, 1983) provides an empirical method for estimating beach erosion associated with a design
storm event. The input parameters for the design storm event described in Vellinga (1983) include the
deep water significant wave height (Hos) and storm surge. The description described in Vellinga
(1983) suggests that the storm surge is exclusive of wave setup which is implicitly included in the
empirical model.( Figure 5-13) shows an example hydrograph of storm surge from Vellinga (1983)
indicating the surge and tide effects and no indication of wave setup. M&N therefore adopted a 100
year ARI storm tide level of 1.74m (exclusive of wave setup) from Aurecon (2013).




                        Figure 5-13 North Sea storm surge hydrograph (Vellinga,1983)




                                                                252662-MN-RP-CO-0001B | 10 November 2025 | Page 33