Cardno Amended flood report July 2018

          Issue:
          The provided information does not demonstrate that the development does not directly,
          indirectly or cumulatively alter the flood characteristics external to the development site for
          all flood events up to and including the defined flood event based on— a) current climate
          conditions; and b) incorporating an appropriate allowance for the predicted impacts of climate
          change.

          Information Required:
          Model the proposed buildings, fences and earthworks associated with the development to
          show that the development will not affect flooding and that the flooding will not impact human
          safety.’

Response
Flow passing through the buildings was to be expected as buildings were modelled off the ground.
No flood storage is removed from the area as the buildings are proposed to be on stumps with the
area underneath inundated. Minimal storage has been removed from the area as a result of the fill
proposed in drawing DA 04E (Attachment A).

Additional hydrologic and hydraulic modelling has been undertaken in this technical memo to resolve
this item. All design events up to the defined flood event (39% to 1% AEP) have been modelled to
meet requirement O22 of the Natural Hazards Overlay Code.

Section 5 provides a summary of the hydraulic results from the modelling. The results indicated
that the proposed development does not cause any negative impacts both internal and external to
the site. Maximum flood depths, water surface elevations, velocities, affluxes and hazards have
been provide in the figures attached (Attachment B).

Item 2:

          ‘Ensure the flood study employs methods that are consistent with one version of ARR. Apply
          appropriate parameters to the RORB model. The Rational Method can be used as a
          ‘checking tool’ but not for calibration of numerical models. Update the modelling and report
          to reflect these changes.’

Response
Whilst the approach was not changed, it was demonstrated that the approach that was adopted was
conservative. Hence it is considered that this item has been addressed.


Item 3:

          ‘Model the proposed buildings and earthworks associated with the development to show that
          the buildings will not affect flooding and that the flooding will not impact human safety.

          Issue:
          The provided information does not demonstrate that the development does not directly,
          indirectly or cumulatively alter the flood characteristics external to the development site for
          all flood events up to and including the defined flood event based on— a) current climate
          conditions; and b) incorporating an appropriate allowance for the predicted impacts of climate
          change.

          Information Required:
          Model the proposed buildings, fences and earthworks associated with the development to
          show that the development will not affect flooding and that the flooding will not impact human
          safety.’