Response to Information Request 10-6-2025 Overland Flow Assessment · OPW25/0042

3. CONCLUSION
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 connect 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).

Three sensitivity assessments were completed, which assessed increased in flow path roughness and increase in flow reporting from external
catchments. Each of the sensitivities highlighted that there were only minor changes resulting, with flow depth only increasing by up 0.1m,
well below the 0.5m freeboard applied to the development. The flow hazard (DV) also had a minor change, with hazard remaining below
0.40m2/s.

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).




NOOSA CALILE I BBNE01676-0001-REP-001-1                                                                                                   17