PA2906-Coastal Hazard Assessment-R1 · MCU21/0212

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erosion prone area undertaken by BMT (2018). It should be noted that the reassessment 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 5.3). This is supported by the assessment of aerial photography
presented in Section 4 which has shown recovery and progradation of the beach adjacent to the site
since severe storm event related erosion in the early 1970’s.

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.

6.1.2       Short-term Erosion (C)
The Department of Environment and Heritage Protection (2013) recommends the calculation of the short-
term erosion based on a 100-year ARI storm event using the method developed by Vellinga (1983).
Figure 15 shows a conceptual representation of the erosion and accretion zones associated with storm



15 October 2021     66 SEAVIEW TERRACE, SUNSHINE BEACH                     PA2906-RHD-ZZ-XX-RP-Z-0001       21