2019-07-09 P&E Agenda - Item 10 - Attachment 1 - Coastal Hazards Risk, Vulnerability and Adaptation Assessment

Noosa Shire Council Coastal Hazard Mapping                                                                23
Erosion Prone Area Assessment




3.6      Shoreline Response to Sea Level Rise (S)
3.6.1    Background Information
         As discussed in BMT WBM (2017), the Noosa CHAP adopts the following sea level rise allowances
         (relative to present-day mean sea level):

         • 2040: 0.2 m

         • 2070: 0.5 m

         • 2100: 0.8 m

         These allowances are based on consideration of the following key studies:

         • IPCC (2014) suggest global mean increases to sea level of approximately 0.3 m by 2050 and
           0.8 m by 2100;

         • DOE, CSIRO & BOM suggest regional mean increases to sea level of approximately 0.14 m by
           2030 and 0.65 m by 2090;

         • Analysis of east coast Australia tide gauge data suggests 3 mm/year increase in mean sea level
           (e.g. CSIRO-ARECRC 2012; Wainwright and Lord 2014); and

         • State planning policy and guidelines that adopt 0.8 m by 2100.

3.6.2    Equilibrium Profile (Bruun Rule) Concept
         The mean sea level has remained at or near the present level for about 6,500 years. During this
         period the shoreline throughout the study area has evolved to a condition of ‘dynamic equilibrium’,
         noting that relatively short-term fluctuations in shoreline position occur (typically in response to
         storm events). In theory, the dynamic equilibrium shape will be maintained as the shoreline moves
         landward in response to SLR. This shoreline response assumes that no significant sediment
         sources or sinks emerge and that the landward migration of the shoreline is not obstructed by
         natural or man-made features.

         The equilibrium profile concept can be simulated by the Bruun Rule (Bruun 1962) which is
         illustrated in Figure 3-4. As SLR gradually occurs, wave, tide and wind related sand transport
         processes influence a higher position on the beach profile, with the shoreline evolving to a more
         landward position to return to equilibrium with the new sea level. There is an upward and landward
         translation of the profile to maintain equilibrium with the prevailing condition at the new SLR
         position.




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