SUPERSEDED Approved Plans & Document OPW25-0042 · OPW25/0042

                     10.2 MAJOR EVENT OVERLAND FLOWS (>10 YEAR ARI)

                     Emergency overflow, for events (>Q10) which cannot be wholly conveyed by
                     underground pipework would be conveyed overland through the development site
                     via a landscaped ephemeral stream.

                     Previous versions of this report relied on simple manning calculations carried out at
                     three (3) nodes along the proposed route through the development site in order to
                     estimate 100 Year ARI flow characteristics and check that such flows could be
                     conveyed safely with the following criteria adopted:-

                     -Maximum velocity x depth product = 0.4m2/sec (QUDM 7.0.4.2)
                     -Minimum channel freeboard = 0.3m (QUDM 9.03.1)
                     -Minimum freeboard to any structural floor=500mm (Council Standards SC6.7).

                     For increased accuracy and certainty and to ensure no impacts to adjacent properties
                     or non-compliant flows through roadways and footpaths performance of the
                     ephemeral stream has now been more accurately modelled by Engeny using specialist
                     software.

                     The Engeny report is included at Appendix B and drew the following conclusions: -

                     Engeny Australia Pty Ltd (Engeny) have been engaged by Calile Malouf Investments Pty Ltd
                     to prepare a Local Overland Flow Assessment for a proposed Operational Works (OPW)
                     development for application resort complex and shop at 3 & 7 Serenity Close Noosa Heads
                     QLD 4567.

                     Detailed overland flow modelling has been completed at a level of detail appropriate for
                     Operational Works approval to confirm Alta Project’s proposed realigned drainage and
                     overland flow design through the site is appropriate in achieving the design requirements for
                     the project.

                     The assessment has found that flows can be appropriately managed through the site via an
                     overland flow path which connects into the Serenity Close cul-de-sac footpath, without
                     impacting adjoining properties or resulting in non-compliant flows with the road and
                     footpath.

                     The assessment found that the finished floor levels of each building achieve a minimum 0.5m
                     freeboard and is able to contain the severe storm event (i.e. 1% (2100) AEP fully blocked
                     stormwater network).

                     Reinforced turf is recommended for the last 20m of channel upstream of Serenity Close
                     (velocity up to 2.30 m/s) and rock protection be placed to manage the outlet velocities (rock
                     size D50 = 200mm and extend 3.6m past the outlet).


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                     A6769/25/SWMP/Rev OpW(A) – Feb 2025                                            Page 20 of 21
                     SH/PL
                                          Brah101 Pty Ltd t/as ALTA PROJECTS

Document Set ID: 23646596
Version: 1, Version Date: 21/03/2025