Smp

3. STORMWATER QUANTITY
   MANAGEMENT
This section assesses the potential impact that the proposed new townhouse development will have on peak flows discharging to the existing
detention basin approved and constructed as part of the original approval (OPW15/0133).

Hydrologic modelling of the catchment has been carried out using WBNM software developed jointly by the University of Wollongong, Rienco
Consulting and Balance R&D. The 2019 version has been used for this investigation, with ARR2019 hydrology.

Modelling has been carried out for the 63%, 50%, 20%, 10%, 5%, 2% and 1% AEP storm events. The following scenarios have been
investigated:

•   Existing Scenario.

•   Developed Scenario.

•   Mitigated Scenario.


    3.1.1     Existing Scenario
The Existing Scenario catchment boundaries and parameters are consistent with the approved report (AquaIntel, 2016). The only changes
made to this scenario was to update the hydrology model to utilise the ARR2019 methodology and update the losses to align with the Noosa
River Flood Study (2017). The existing catchment plan is shown in Figure 2.1, with the proposed townhouse development located in SUBB.
The existing scenario sub-catchment areas and fraction impervious values for each sub-catchment are tabulated below in Table 3.1.




Figure 2.1: Existing Scenario Catchment Plan




73 EUMUNDI - NOOSA ROAD, NOOSAVILLE I BBNE00529_0002_0001-REP-001-0                                                                    10