2019-07-09 P&E Agenda - Item 10 - Attachment 1 - Coastal Hazards Risk, Vulnerability and Adaptation Assessment

Noosa Shire Council Coastal Hazard Mapping                                                                 7
Storm Tide Hazard Assessment




         process of advancement and retreat of the instantaneous shoreline position on a timescale that is
         of the order of the incoming wave period (~12 s for large swell conditions). A preliminary wave
         runup assessment is presented in Section 3.5.1.3, noting that wave runup and overtopping are key
         considerations when designing coastal structures and may need further assessment during the
         options analysis stage of the Noosa CHAP.

2.2.2    Lower Noosa River Storm Tide Assessment
         Aurecon (2013) produced storm tide hazard mapping throughout the tidal extent of the Noosa River
         catchment using inundation modelling techniques. In summary, this involved the application of
         representative ‘surge plus tide’ boundary conditions at the entrance to the Noosa River and
         simulation of the resulting lower river floodplain inundation. The current climate 100 year ARI
         boundary condition is shown in Figure 2-1.




          Figure 2-1    100 year ARI surge plus tide boundary condition applied at the entrance to the
                                          Noosa River (Aurecon 2013)


         Future climate 2100 scenarios involved adding a 0.8 m SLR allowance offset to the boundary
         condition shown in Figure 2-1. In addition, a morphological response to SLR across the lower
         Noosa River and flood tide delta was represented by raising the bathymetry elevation by an
         amount equivalent to the SLR allowance. Full details of the modelling approach are provided in
         Aurecon (2013).

         To develop lower Noosa River storm tide mapping for the additional 2040 and 2070 planning
         horizons required by the CHAP, the modelling approach described by Aurecon (2013) has been
         adopted. This simply involved application of the existing inundation modelling tools with surge plus
         tide and bathymetry boundary condition adjustments using the methodology described in Aurecon
         (2013). The SLR assumptions for each planning horizon are summarised in Table 2-1.

         It is noted that the assessment mapping presented in Appendix A classify the inundation hazard in
         terms of depth only. Other hazard definition information, such as inundation velocity, is also
         available to the Noosa CHAP and may be considered as part of the risk and vulnerability
         assessment (QCoast2100 Phase 5).



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