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

            the minimum requirement for seawalls is a 50 year ARI event at stipulated in the Prescribed
280         Tidal Works Code in the Coastal Protection and Management Regulation 2017).
      5.    Reason 6; it is acknowledged that further set‐back beyond 6m would further reduce the risk of
            erosion affecting the proposed development; however, the proposed geotechnical design
            ensures that, irrespective of coastal erosion and subsequent slope failure and reprofiling, the
            pool structure will remain in place following a 100 year storm tide and wave erosion event and
285         recession due to sea level rise of 0.3m by 2050.
      6.    Draft Planning Scheme; Coastal Protection overlay Code
            a)    PO1; the proposed micro‐piled design allows for natural fluctuations of the coast and
                  foreshore without the need for additional coastal protection works, for events up to the
                  100 year climate change to 2050 storm tide and wave event, and recession due to sea
290               level rise of 0.3m by 2050.

                 Coastal erosion events larger than the 100 year event would further impact on the
                 ultimate erosion scar but appear unlikely to compromise the proposed micro‐pile design
                 as further erosion of the dune can occur whilst maintaining an adequate factor or safety.
295              Certification of the final Geotechnical design confirming this is recommended. Under
                 extreme event, failure may still occur.

            b)    PO3; dune crest is not impacted by the proposal. Wave overtopping does not occur due
                  to the height of the dune. Storm tide inundation has been assessed and the miro‐pile
300               design adequately mitigates the risk for all storm tide and wave events up to the 100
                  year climate change 2050 event.

                  Coastal creeks and mangroves are not impacted.
            c)    The development proposal is not located as far landward as possible as it could be 3 to
305               5m further to the west. PO5; the development proposal does not comply as it is located
                  seaward of the coastal building line.
      CONCLUSION

      The of proposed development of a swimming pool can be accommodated within the Coastal
      Building Line by incorporation of the modified geotechnical design with a number of micro‐piles
310   without compromising the future coastal management options for this section of coast. The design
      of the piled foundations prepared by Core Engineering dated 24 September 2019 will provide
      protection of the swimming pool and subsequently the house by adequately managing erosion from
      impacting on the pool structure for all storm tide and wave events up to the 100 year climate change
      2050 event.

315   The Coastal Building Line is an arbitrary line set by the former Beach Protection Authority to allow
      for natural shoreline movements (i.e. erosion and accretion) associated with storm events.
      In terms of coastal engineering issues, we conclude that the inclusion of the modified piled
      foundation design by Core Engineering should ensure that the pool will withstand erosion associated
      with a 100 year ARI storm and recession due to sea level rise of 0.3m by 2050 (i.e. the adopted
320   design life of the swimming pool).




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