PA3660-Coastal Hazard Assessment - 4 arakoon

                                              Project related




6.2             Erosion Prone Area Reassessment
The declared erosion prone area for the Noosa Shire Council area is provided on Department of
Environment and Science Plan Number NOS3A dated 8 July 2015 (refer Appendix B). This shows an
erosion prone area width for Sunshine Beach of 175 metres measured inland from the seaward toe of the
frontal dune.

Noosa Shire Council has completed a Coastal Hazard Adaptation Study (CHAS) through the QCoast2100
program. Phase 3 of the CHAS involved refining coastal hazard mapping, including reassessment of the
erosion prone area was undertaken by BMT (2018). The erosion prone area calculated by BMT (2018) for
Sunshine Beach was 118m 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.

6.2.1           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 a long-term erosion rate of 0.03 metres/year for Sunshine Coast at beach
profile line ETA 602, located approximately 1.2km south of Noosa Headland (Figure 6-1). Table 6-1
provides a summary of BMT (2018) estimated long-term erosion for 2040, 2070 and 2100.


Table 6-1 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


The subject site is located approximately 700m south of Noosa Headland which plays a significant role in
sediment transport processes along this beach as discussed in Section 5.3. This is supported by the
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.

Given the long-term stability of this section of coast a nominal 10m has been adopted in accordance with
the Department of Environment and Heritage Protection (2013).




11 April 2024         4-6 ARAKOON CRESCENT, SUNSHINE BEACH                   PA3660-RHD-XX-ZZ-RP-Z-0001       25