24-01-2020 - Appeal No. 245 of 2019 - Final Order of Judge Rackemann · 51987.2951.01

Working Notes:
M Design and Fourteen Enterprises Pty Ltd as trustee v Noosa Shire Council -
42 Seaview Terrace, Sunshine Beach

6.     Erosion Prone Area Reassessment
Erosion Prone Areas are declared under section 70 of the Coastal Protection and Management Act
1995 and identifies land that may be vulnerable to coastal erosion or tidal inundation over a 100
year planning period. The Erosion prone area is used in the assessment of development triggered by
the Coastal Management District.

The ‘Coastal Hazards Technical Guide’ prepared by the Department of Environment and Heritage
Protection (2013) provides guidance on the calculation of an erosion prone area. The erosion prone
area width is based on the following:
     short-term erosion from extreme storm events (e.g. a tropical cyclone);
     a dune scarp component to accommodate slumping of the erosion scarp following short-
        term erosion;
     long-term erosion associated with a deficit in sediment supply;
     shoreline recession due to sea level rise of 0.8 metres associated with climate change by the
        year 2100; and
     a 40% safety factor.

The Erosion prone area is calculated using the following equation:

                𝐸 = {(𝑁 × 𝑅) + 𝐶 + 𝑆} × (1 + 𝐹) + 𝐷                     equation 1

Where:
E=     Erosion Prone Area (metres)
N=     planning period (years)
R=     rate of long-term erosion (metres/year)
C=     short-term erosion from the design storm event (metres)
S=     recession due to sea level rise (metres)
F=     factor of safety (0.4)
D=     Dune scarp component to allow for slumping of the erosion scarp (metres)

The erosion prone area equation was created by the former Queensland Beach Protection Authority
in the late 1970’s and has not been altered since that time. The equation is based on a number of
assumptions, including:
      The beach and dune profile consists of unconsolidated loose sand with uniform physical
         characteristics throughout the profile.
      There are no physical features (e.g. headland) that would influence sand movements.
      Storm events occur over a sufficient period of time to allow for development of an
         equilibrium storm profile of the beach.
      The long-term erosion trend is independent of recession due to sea level rise.

These factors mean the erosion prone area is a very conservative assessment of erosion
vulnerability. When combined with the 40% safety factor the overall conservatism of the method is
further exacerbated.

The Subject Site is located entirely within the Erosion prone area as defined on Department of
Environment and Science Plan Number NOS3A dated 8 July 2015 (refer Figure 3-3). The Erosion
prone area for this section of coast is currently 175 metres measured inland from the seaward toe of
the frontal dune (refer Figure 3-3). The assessment of the components of the erosion prone area
presented in Plan Number NOS3A was originally undertaken in the 1980’s by the Queensland Beach
Protection Authority with only the recession due to sea level rise being updated in 2015.
                                                                                                  28

                                                                                     127738:14917433_1
                                               038
                                                                                                         47