2021-01-18 GC - Item 3 - Attachment 2 - Phase 7 Project Summary Coastal Hazards Adaptation Plan

    Noosa Shire Council Coastal Hazard Adaptation Plan: Project Summary                                          6
    Methodology




              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 QCoast2100 Minimum
              Standards and Guidelines). A detailed remapping of erosion prone areas was undertaken by BMT,
              in accordance with the Queensland Government Coastal Hazard Technical Guide (DEHP, 2013).

              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.

              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.

2.2.2.3 Permanent Sea Level Rise
              The State EPA mapping defines permanent tidal inundation due to sea level rise (SLR) at 2100 as:

              • Present-day Highest Astronomical Tide (HAT) plus 0.8 m SLR.

              The hazard area is then obtained by extrapolating the water level across land. Areas adjacent to tidal
              waters where the ground elevation falls below the threshold water level are deemed to be within the
              hazard area.

              The SLR hazard information provided by the State is useful for ‘first-pass risk screening’ only and
              does not provide sufficient information regarding likelihood and consequence to undertake a more
              detailed risk assessment. To address this issue, SLR hazard mapping including depth classification
              was developed for the Noosa CHAP planning horizons. The adopted approach generally follows the
              State definition, whereby a threshold water level (mAHD) is defined by consideration of HAT plus an
              appropriate SLR allowance. The water level mapping assumptions are summarised in Table 2-2.
              These thresholds for different locations throughout the study area consider Maritime Safety
              Queensland published tidal planes (MSQ 2017) along the open coast and within the lower Noosa
              River. Linear interpolation 1 of the water level between the sites has been adopted with the Munna
              Point and Tewantin levels extending into Lake Cooroibah/Cootharaba and Lake Weyba respectively.




1
    Hydralogic, Future Tidal Inundation Mapping for Noosa River, 2018