ECM_22343537_v1_Coastal Hazard Assessment · 132000.200173.1

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              by BMT (2018) was at a beach compartment scale and did not provide site-specific estimation of erosion
              vulnerability.

              The following sections will review each component of the Erosion prone area based on site specific
              conditions.

              6.1.1       Long-term Erosion (N x R)
              The long-term erosion component is based on the selected planning period (N) and the average annual
              rate of long-term erosion (R).

              In relation to the planning period, the Department of Environment and Heritage Protection (2013) states,
              “The long-term erosion component (excluding sea level rise) of the calculation is often cyclical in nature
              and typically of a decadal scale. For this reason, it is considered the estimated annual rate of long-term
              erosion is only applied for a 50-year period”. Where there is no clear evidence of long-term erosion
              trends, the Department recommends a nominal provision of 10 metres.

              The annual rate of long-term erosion (R) reflects changes to sediment supply to a beach and where there
              is a long-term deficit in sediment supply this results in a longer-term recession of the shoreline. BMT
              (2018) has calculated the long-term erosion rate for Sunshine Coast at beach profile line ETA 602. Table
              3 provides a summary of BMT (2018) estimated long-term erosion for 2040, 2070 and 2100.


              Table 3 Summary of Long-Term Recession Results from BMT (2018)

                                                         Annual Recession                    Long-Term Recession (m)
               Beach                    Survey Profile
                                                           Rate (m/year)       2040 (N=23)         2070 (N=53)         2100 (N=3)

               Sunshine Beach             ETA 602.0            0.03                0.7                 1.6                2.5


              BMT (2018) calculated an annual long-term erosion rate of 0.03 metres/year for Sunshine Beach.
              However, the subject site is located approximately 210m south of Noosa Headland which will influence the
              sediment transport processes along this section of coast by trapping the long-term net northerly littoral
              transport of sand (discussed in Section Error! Reference source not found.). This is supported by the
              assessment of aerial and satellite imagery presented in Section 3 which has shown recovery and
              progradation of the beach adjacent to the site since severe storm event related erosion in the early 1970’s.
              Further, Section 3 highlights sensitivities associated with reporting intervals for long term recession and
              the need to select suitable start and end dates for any analysis, which are not influenced by episodic
              erosion events.

              It is noted that BMT (2018) had adopted a nominal 10m value for long-term erosion for erosion prone area
              calculation over a 100-year planning period and this is in accordance with the Department of Environment
              and Heritage Protection (2013) methodology. This is consistent with the Department of Environment and
              Heritage Protection (2013) methodology. However, it does not consider the effect of the site’s proximity to
              Noosa Headland which will reduce long-term erosion.

              Long-term erosion of 0 metres is considered more realistic given the influence of Noosa Headland which
              would act in a similar fashion to a groyne by trapping sand moving north along the coast with the
              prevailing south-easterly wave climate.




              13 February 2023         2 ARAKOON CRESCENT, SUNSHINE BEACH                                    PA3303       25


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