Reference Document - RAL23/0013.02 - Part 2 (As Published)

2.2.      Flood Investigation
The proposed development footprint is currently largely located outside of the NSC Flood Hazard Overlay
Mapping; however, the rear of lot 8 and 9 is partially inundated in the 1% (2100) AEP. The Noosa Plan Flood
Hazard Overlay Code identifies that any development / filling below the 1% (2100) AEP flood level must
demonstrate that no off-site impacts and no loss of flood plain storage is demonstrated.

Council’s Pomona Flood Model was utilised to represent the development proposal and demonstrate the
requirements of the Flood Hazard Overlay Code.

2.2.1.    Flood Model
The NSC Pomona Flood Model was utilised as the basis for the flood assessment to represent flooding in
the 1% (2100) AEP event. The model was setup and run for the Existing and Proposed Scenarios. The
model was utilised in full, with the following updates made to represent these two scenarios:

Existing (E05)

         Reduce model grid size from 5m to 2m.
         Update model terrain to utilise 2015 Lidar and site survey.
         Model was run using HPC and the latest TUFLOW engine (version 2020-10-AA).
         Represented 1D channels in 2D with smaller grid size.
         Site survey of 25 Pavilion St, Pomona, prior to development works.
         Represented design for 25 Pavilion St, Pomona, including:
              o surface of preliminary engineering design
              o drain in 3m easement (approx. 0.4m deep at 1% grade).
              o area of cut, 1,250m2 and 0.1m deep.
         Site survey of 33 Pavilion St, Pomona.

Proposed (P06)

         Update model terrain to include updated engineering design for 33 Pavilion St, Pomona (supplied
         by TOD Consulting, 21 September 2023).

2.2.2.    Existing Scenario (E05)
The existing case model has been setup and run for the 1% (2100) AEP flood event. The results of this have
been used as the basis for assessing the potential impacts that may result from the development.

Appendix C details the existing flood extent in relation to the development site.

2.2.3.    Proposed Scenario (P06)
The proposed case model has been setup and run for the 1% (2100) AEP flood event, which incorporates
the proposed development site. Appendix D details the proposed flood extent in relation to the
development site. An indicative site plan is overlaid on this figure to highlight how the development relates
to the flood extent.

2.2.4.    Afflux
Afflux mapping has been undertaken for the 1% (2100) AEP events to identify whether there are any
impacts resulting, and if so, whether an alternative development arrangement needs to be investigated.




23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona                            Page 25