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

Noosa Shire Council Coastal Hazard Mapping                                                                  10
Erosion Prone Area Assessment




         an elevation above the threshold water level. This component has also been reassessed for the
         planning horizons relevant to the Noosa CHAP (see Chapter 4).

         The EPAs determined by the State define a hazard extent at a single specified planning horizon
         (the year 2100) and probability (representative 100 year ARI). The erosion prone areas are
         therefore useful for ‘first-pass risk screening’ however do not provide sufficient information
         regarding likelihood and consequence to undertake a more detailed risk assessment in accordance
         AS/NZS ISO 31000:2009, the SPP or other State guideline documents (such as the QCoast 2100
         Minimum Standards and Guidelines). This issue has been addressed through the erosion prone
         area hazard assessments described in this Chapter.

3.2      Calculated Erosion Distance Assessment
         The potential coastal erosion hazard throughout the study area arises from a combination of:

         • The physical processes that are causing (or threatening to cause) erosion;

         • The assets and values potentially affected by the erosion; and

         • The timeframe over which the threat may act upon the assets and values.

         In order to assess the erosion hazard for the open coast beaches throughout the Noosa region, it is
         necessary to understand which areas are presently within the short term storm erosion zone and
         areas that may become threatened in the future.

         To effectively assess the coastal erosion hazard a vulnerable zone is typically determined for a
         specific planning period. The erosion vulnerability zone should include the following components,
         consistent with the Queensland Government Coastal Hazard Technical Guide (DEHP, 2013):

         • Short term storm erosion;

         • Continuation of the long term historical shoreline position trend (if this can be identified);

         • Cyclic morphological change observed at river and creek mouths (not a significant issue at this
           location due to training of the southern shoreline of Noosa River); and

         • Additional future effects of climate change induced sea level rise.

         The selected planning period influences:

         • The design event characteristics adopted for the short term erosion assessment;

         • The duration that the long term erosion component is applied; and

         • The choice of an appropriate sea level rise projection.

3.2.1    Open Coast Calculated Erosion Distance Formula
         The open coast erosion hazard areas are determined to cater for potential erosion of the dune
         system over a specified planning period. Both short term (storm-related) and longer term (gradual)
         trends are included in the assessment together with an allowance for potential sea level rise
         associated with climate change. Provision is also included for a factor of safety on the estimates
         and an allowance made for slumping of the dune scarp that is often observed after significant storm



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