Stormwater Mgmt Plan

SC-8407 – 45 Maple Street, Cooroy                                                            10


4.4      Modelling Results
A node layout plan is included in Appendix B of this report and the resultant peak flow rates are displayed
in Table 4.3 & 4.4.

                                                                  3
                                                   Peak Flow (m /s)
                                    AEP (%)
                                                   Pre Development

                                    50 (Q2yr)       0.093 (30min_1)

                                    20 (Q5yr)       0.137 (20min_10)

                                    10 (Q10yr)      0.166 (30min_3)

                                    5 (Q20yr)       0.194 (30min_3)

                                    2 (Q50yr)       0.222 (15min_8)

                                    1 (Q100yr)      0.245 (15min_8)

                            Table 4.3 – Pre-Development Peak Flow Rate Results


                                                                  3
                                                   Peak Flow (m /s)
                                    AEP (%)
                                                   Post Development

                                    50 (Q2yr)       0.082 (20min_10)

                                    20 (Q5yr)       0.120 (10min_5)

                                    10 (Q10yr)      0.132 (30min_3)

                                    5 (Q20yr)       0.151 (30min_3)

                                    2 (Q50yr)       0.161 (15min_8)

                                    1 (Q100yr)      0.175 (15min_8)

                      Table 4.4 – Post-Development (mitigated) Peak Flow Rate Results


As can be seen in Tables 4.3 & 4.4 the post-development peak flow rates to the existing drainage system
compare well to that of the existing pre-development site discharges. This is due to the large volumes of
on-site detention proposed to be included as part of the development.