Reference Document - Coastal Hazard Assessment - MCU24 0094 · MCU24/0094

                                  33 Ross Crescent, Sunshine Beach – Coastal Hazzard Assessment | 33 Ross Crescent Family Trust




The assessment's determination of dune height relied on an iterative approach, which is discussed in more
detail in Section 6.3.2. The resultant dune height determined through this iterative process was 11m. The
profile width from the dune height to depth of closure (-12m) is 600m. Therefore, a profile width of 600m, a
depth of closure of -12m together, and a dune height of 11m AHD provide a recession due to a sea level
rise of 21m (Table 6-4).

TABLE 6.4: SUMMARY OF SHORELINE RECESSION DUE TO SEA LEVEL RISE AT 33 ROSS CRESCENT, SUNSHINE
BEACH
 Assessment       Profile Width    Dune Height      Depth of Closure      Sea Level Rise      2100 Shoreline Recession
                      (m)            (m AHD)             (m AHD)                 (m)                       (m)
 RHDHV (2024)         600                7                  -12                  0.8                       25
 M&N (2025)           600                7                  -12                  0.8                       25

6.3.2.   Recession due to Sea Level Rise (S)
Immediately following severe storm erosion events on sandy beaches, a near vertical erosion scarp will
form at the dune edge. Over time the erosion scarp will slump to the natural angle of repose of the sand.
Since the short-term erosion only accounts for shoreline recession due to wave runup for cases where the
foreshore is not overtopped, the Queensland Hazard Technical Guide (DEHP, 2013) recommends adding
this dune scarp component when calculating erosion width.

The dune slumping component at the end of the 100-year planning period has been determined by
combining the long-term erosion, short-term erosion and recession due to SLR which equates to 59m.
Applying the angle of repose for dune slumping (35 degrees) a dune scarp component of 10m was adopted
for 33 Ross Crescent, Sunshine Beach (refer Figure 6-6, below).
6.3.3.   Dune Height
The dunes along this section of coast are classified as 'high dunes'. Determining the recession caused by
sea level rise (S) necessitated identifying the erosion profile to ascertain the dune height at this specific
location. The assessment employed an iterative methodology to determine the dune height, involving an
initial calculation of S using a test dune height. Subsequently, the dune height was refined until the erosion
width intersected the profile at the same dune height utilised in the sea level rise recession calculation.

For this evaluation, a dune height of 7m was established (Figure 6-6).




                                                                                                                            25