Attachment D - Stormwater Report · MCU18/0013

       2.2             Lawful point of discharge
      Stormwater runoff from the existing site initially falls east as overland flow, prior to concentrating due to the
      slope of the land and discharging to Sunshine Beach.

      Stormwater runoff from impervious areas of the development is proposed to be directed to an underground
      tank located at the rear of the site. Runoff from the tank shall discharge via infiltration or shall surcharge and
      discharge east to Sunshine Beach when at capacity as per existing conditions. Stormwater runoff from
      pervious areas at the rear of the site shall similarly discharge east to Sunshine Beach. Refer to Appendix B
      for further information.

       2.3             Flooding
      According to the NSC planning scheme flood hazard overlay mapping the development site is not subject to
      flooding from any sources.


3. Stormwater Quantity Management

      The stormwater quantity analysis of the existing and developed site conditions has been undertaken with
      reference to the requirements and procedure outlined by:

                Queensland Urban Drainage Manual (QUDM)
                Australian Rainfall and Runoff Volumes 1 & 2 (Aust R&R)

       The following section of the report discusses the proposed development’s impact on peak stormwater runoff
       and total runoff volume from the site and compares the existing site condition to ensure a no worsening
       effect to downstream land.

       3.1             Catchment Summary
       Pre-Developed Site

      The existing site consists of vacant land. Stormwater runoff initially falls east as overland flow prior to
      concentrating and discharging to Sunshine Beach.

      The existing site area is approximately 635m2 and is fully pervious (fi=0.0).
       Post-Developed Site

      The development involves the construction of a single dwelling and ground level features. Runoff from
      impervious areas of the development is proposed to discharge via infiltration or overland to Sunshine Beach
      when the tank surcharges. Runoff from pervious areas at the rear of the site shall similarly discharge
      overland to Sunshine Beach as per existing conditions.

      The catchment area remains unchanged at approximately 635m 2. The total impervious area was calculated
      to be approximately 420m2 which equates to 66% fraction impervious (fi=0.66).

       3.2             Stormwater Detention & Infiltration
      Stormwater runoff from developed areas of the site shall be directed to a proposed infiltration tank which
      shall incorporate stormwater detention to ensure the peak flow rate and total runoff volume discharging to
      Sunshine Beach are reduced to pre development levels.
      The Atlantis Flo-Tank Modular tank system was adopted as part of the stormwater design. An infiltration rate
      of 0.6m/d was adopted based on information contained in the geotechnical report prepared by Soil Surveys.

      Refer to Table 1 and Appendix B for further details of the proposed system.



                                        24 Arakoon Street, Sunshine Beach QLD 4567
Job No – S18-003                           STORMWATER MANAGEMENT REPORT                                              2