Attachment 1 - Stormwater Management Plan

            3. STORMWATER QUANTITY
                    3. 1. P R E – P O S T C O M P A R I S O N

            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.
            Due to the small nature of the development, a minimum time of concentration of 5 minutes
            has been used for each contributing area.

            The model used for DRAINS for 53 Doonella Street is shown below in Figure 3.1 – DRAINS
            model Layout for 53 Doonella St, with the same configuration used for 55 Doonella Street.




                                       Figure 3.1 – DRAINS model Layout for 53 Doonella St

            The configuration of the catchment areas for pre-development and post development areas
            are shown in Figure 3.2 – DRAINS Pre-development catchments and Figure 3.3 – DRAINS
            Post-development catchments respectively. The developed flow rates were determined
            from the sum of flow values at the source catchments prior to any impacts from the
            attenuated model.




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