RFI - updated flood investigation report

      5. CONCLUSION
      PEAKURBAN have completed a Flood Investigation to support the Reconfiguration of Lot
      application for the development at 60 Glenridge Drive, Cooroibah. The objective of this
      investigation was to design an appropriate road crossing to service the development,
      demonstrate that no impacts and no loss of flood plain storage will result from the proposed
      development (and associated earthworks).
      This investigation demonstrates that a suitable development strategy has be developed
      without creating any impacts to any adjoining property owners. Afflux maps for the 63.2, 39%,
      10%, 1% and 1% (2100) AEP flood events and PMF provided in Appendix H demonstrate this.
      The investigation has found that there is a reduction in peak flows and increase in flood storage
      provided. As such, any further formal on-site detention is not recommended as development
      has been designed to achieve the outcome of non-worsening.
      The proposed development lot building envelopes are located above the 1% (2100) AEP, and
      it is recommended that finished floor levels of future dwellings achieve a minimum 0.3m
      freeboard above the DFE or the PMF level as detailed in Table 4-5.
      This flood investigation plan successfully demonstrates that:
           •        The site is developed to create building envelopes that are flood free and enable
                    future finished floor levels to be a maximum of 0.3m above the DFE or the PMF
                    event.
           •        There is no impact to flood levels to adjoining properties as a result of this
                    development.
           •        Non-worsening of peak flows downstream of the development is achieved.
           •        Internal Road has been designed to achieve flood immunity in the 10% AEP event
                    and trafficable in the 1% AEP event.
           •        There is no loss in flood plain storage, with the proposed earthworks actually
                    increasing the available storage.
           •        Severe storm assessment found that future dwellings with freeboard would remain
                    free in the 1% (2100) AEP scenario with all culverts 100% blocked.




21-0288-FS001-V3 | Flood Investigation | 60 Glenridge Drive, Cooroibah                                    | 17