Attachment 7 - Flood Impact Assessment - Covey · 132005.638.06

         3.15    Results

         Results from all modelled scenarios were exported and peak water surface levels have been mapped to
         demonstrate conveyance within the overland flow paths. A comparison between the existing and
         developed peak water surface levels, velocities and hazards was undertaken for all scenarios. The change
         in water surface level was mapped to ensure no unacceptable offsite impacts were experienced and
         ensure risk and flood hazard will be appropriately managed. Refer to the Flood Maps in Appendix C for
         further detail.

         Generally, it was demonstrated that the existing and developed overland flow paths have an adequate
         conveyance of overland flow from upstream external catchments for all simulated events.

         3.15.1 Onsite Impacts
         In the developed scenario, during the 1% AEP climate change event, the water surface level on the
         western internal roadways and drains increased between by up to 300 mm. However, this flow is safely
         conveyed through the site without inundating the proposed buildings. In addition, the hazard (depth x
         velocity) on the internal roads is acceptable (< 0.6 m2/s). This increase is also noted immediately upstream
         of the proposed culverts (DEV01). This is expected as the proposed road crossing the channel will cause
         head loss at this location as the flow enters the culverts. However, the results also demonstrated that the
         road crossing has an immunity up to the 1% AEP climate change event. Similarly, within the drains on the
         eastern side of the site, flows which are contained within the existing drains demonstrated increases of
         up to 250 mm.

         The northern section of the site, downstream of the area of works, contains vegetation and existing
         overland flow paths. Increased in water surface level of 20-50 mm were noted in these areas. However,
         these areas are part of the subject site and are unlikely to be developed, therefore the impacts are not
         deemed an actionable nuisance.

         The water surface levels in the vicinity of the HES basin and proposed buildings have been provided as
         shown in Figure 3-5 and Table 3-4. The levels can be used to set the minimum floor levels as required.




Flood Impact Assessment                                                                                      Page 15 of 25
Project No 244035 | Ref No M25-0479Rpt – Issue A – January 2026