Revised SWMP

                                             Figure 3.1 – DRAINS Pre-development catchment




                                            Figure 3.2 – DRAINS Post-development catchments

The results of the modelling against the range of design storms for the development under the existing and
proposed development conditions are shown in Table 3.1 Existing and proposed unmitigated site peak discharge.

                                   Table 3.1 Existing and proposed unmitigated site peak discharge

                                                                          Pavilion Street
                                                                                                        Qchange
                                             A.E.P                Qexisting   Qproposed    Qchange       (%)
                                                                  (m³/s)      (m³/s)       (m³/s)
                                         63.2% AEP                 0.035       0.033       -0.002         -6%
                                            0.5 EY                0.052        0.057       0.005         10%
                                            0.2 EY                0.081        0.084       0.003          4%
                                           10% AEP                0.100        0.102       0.002          2%
                                           5% AEP                 0.124        0.126       0.002          2%
                                           2% AEP                 0.156        0.156       0.000          0%
                                           1% AEP                 0.172        0.172       0.000          0%
Despite the increase in impervious area, the combined effect of the changes resulting from the development will not
alter peak flows to a significant extent. The combined peak discharge from both lots increases the site run-off by a
maximum of 5L/s, or 2.5L/s for each lot. Within the context of the locality, being low density residential sites on large
allotments, this level of increase will not result in significant impacts or nuisance to the downstream nor damage to
the downstream property. Attenuation is therefore not considered necessary for the future development of the lots
where total impervious area of the lots is up to 40% impervious. Beyond this, further assessment may be necessary.




Project number 20220217
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File 20220217 Pavilion St SWMP Rev1.docx, 2023-04-19 Revision 1

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