12. APP G. Stormwater Management Plan

                Table 5.1: Stormwater Detention Basin Summary
                                         Parameter

                                          Base Area                                                     144m2

                                             Depth                                          1.8m (including 0.3m freeboard)

                                      Storage Volume                                                    280m3

                                    Outlet Arrangement                                             Ø100mm orifice

                                         Weir Width                                                      0.4m

                                         Weir Height                                                     1.2m
                The detention basin parameters listed in Table 5.1 were calculated using XPRafts. An iterative
                method was used to adjust the parameters until the catchment flows were reduced to the
                predevelopment flows. Hydrographs relating to the detention basins, including basin storage
                volume, have been included in Appendix F.

5.1.3           MODEL RESULTS
                The discharge rate at each discharge point is tabulated below for the existing, developed and
                mitigated scenarios. This table shows that the proposed detention basin is successful in
                mitigating the developed discharge back to existing rate for all of the ARI storm events.

                Table 5.2: Stormwater Discharge Rates
                                         Existing             Developed             Mitigated          Impact
                        ARI              Scenario              Scenario             Scenario             (%)


                    Q1 (m3/s)               0.039                 0.161                  0.031          -21%

                    Q2 (m3/s)               0.054                 0.206                  0.033          -39%
                    Q5 (m3/s)               0.076                 0.239                  0.037          -51%
                   Q10 (m3/s)               0.094                 0.269                  0.046          -51%
                   Q20 (m3/s)               0.117                 0.311                  0.071          -39%
                   Q50 (m3/s)               0.135                 0.342                  0.105          -22%

                  Q100 (m3/s)               0.155                 0.408                  0.154           -1%




139 Eumundi Noosa Road & 30 Lionel Donovan Drive, Noosaville Service Station and Retail Site—Stormwater
Management Plans
Hyder Consulting Pty Ltd-ABN 76 104 485 289                                                                                   9
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