ECM_22343537_v1_Coastal Hazard Assessment · 132000.200173.1

                                                            Internal use only




                       method implies that the erosion prone area has sufficient width to accommodate
                       the design storm erosion in 100 years’ time, when all of the estimated long-term
                       erosion has occurred. Therefore, it also follows that for much of the 100-year
                       planning period, the erosion prone area is sufficient to accommodate a larger
                       storm than the one selected for design purposes. In fact, in the most critical last
                       10 years of such a planning period, there is only a 10% probability of occurrence
                       of the design storm. Thus, the risk of a storm breaching the entire erosion prone
                       area at some time during the 100-year period will be significantly less than 63%.”

              BMT (2018) adopted a combination of a 100-year ARI Storm Tide level and 100-year ARI significant wave
              height as the design storm event for the reassessment of erosion prone areas with Noosa Shire Council.
              It should be noted that the joint probability of a combined 100-year ARI storm tide and 100-year ARI
              significant wave height is likely to be significantly greater than a 100-year ARI storm event. This
              combination of design storm tide level and wave height will be adopted for the site-specific reassessment
              of the erosion prone area reported herein.

              An additional assessment of short-term erosion will be undertaken for a more extreme event to assess the
              vulnerability of the proposed house and pool to assist with foundation design. The design parameters for
              the assessment of the short-term beach erosion and scenarios are presented in Table 4.
              Table 4 Design Storm Events for Short-term Beach Erosion Assessment
                                                                                    Storm Event
                                 Storm Component
                                                                  100-year ARI              Extreme Event
                                 Significant Wave Height               6.2m                       6.2m
                                                                                              1.84m AHD
                                 Storm Tide                        1.74m AHD
                                                                                        (500 year ARI storm tide)
                                 Sea Level Rise                           -                       0.8m

              Figure 19 and Table 5 present the results of the modelled storm erosion associated with the above 100-
              year ARI design storm event. This shows storm erosion of 22 metres measured from HAT position on the
              current beach profile (pre-storm profile) to the toe of the erosion scarp.

              The extreme event scenario adopted in Table 4 incorporates the impact associated with a 0.8m increase
              in mean sea level in addition to a 500 year ARI storm tide event (i.e. 1.84m AHD). This provides for a total
              water level of 2.64m AHD for this assessment and therefore incorporates additional erosion associated
              with the adopted sea level rise projection. This allowance for sea level rise is consistent with the
              Queensland Government policy for the planning period to 2100.

              Figure 20 and Table 5 present the results of the modelled storm erosion associated with the extreme
              design event. This shows a storm erosion cut of 47 metres is predicted to occur and will be used to inform
              slope stability assessment and foundation design by the geotechnical engineering consultants, Tectonic
              Geotechnical Pty Ltd.




              13 February 2023         2 ARAKOON CRESCENT, SUNSHINE BEACH                                PA3303     27


Document Set ID: 22343537
Version: 1, Version Date: 16/03/2023