RFI - 20210153 Maple St SWMP

 STORMWATER QUANTITY

     3.1. Pre-Post Comparison
The site has been modelled using the DRAINS software to model the peak flow hydrology off the site.
In accordance with ARR2019, an Initial Loss-Continuing Loss (IL-CL) model has been used to assess
the proposed development against the ensemble of storm temporal patterns for the East Coast North
region.

The loss parameters and temporal patterns have been imported from the ARR Datahub, and rainfall
intensities have been imported from the Bureau of Meteorology IFD rainfall data allowing for a 20%
increase to rainfall depths to account for future climate change patterns.

The parameters obtained from the Australian Rainfall and Runoff (ARR) Data Hub for the location
and the rainfall IFD data obtained from the Bureau of Meteorology have been imported into Drains
to generate the storm events. The models have been run using the ensemble of storm events for
1EY, 50%, 0.2EY, 10%, 5%, 2% and 1% Annual Exceedance Probability (AEP) for durations from 1
minutes to 24 hours to determine the critical storm duration and the mean peak flowrate from the
storms. Refer to Appendix B DRAINS Modelling Parameters & Results for further details of the
parameters used in the modelling.

As identified in the Noosa Shire Council Works Code, climate change impacts are to be accounted
for in the stormwater modelling. Discussions with Council have indicated that a 20% increase to the
Bureau of Meteorology rainfall data will provide an acceptable allowance, therefore a climate
change factor of 1.2 has been applied to the BOM data to account for this.

The model used to represent the development is shown below in Figure 3.1 – DRAINS model layout.




                                           Figure 3.1 – DRAINS model layout




Project number 20210153
File RECOR Preliminary Stormwater Management Report - 20210153.docx, 2022-03-31                                 Page 11 of 27
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