Appendix D- Stormwater Management Plan · MCU23/0078

                    Table 5: Comparison of Rational Method & XP Storm Existing Peak Flows – Site A (m3/sec)
                            AEP (%)     ARI (Years)    Rational Method Result     XP Storm Result
                              63.21              1                    0.286                       0.134
                              39.35              2                    0.344                       0.197
                              18.13              5                    0.520                       0.431
                                10               10                   0.641                       0.613
                                5                20                   0.765                       0.813
                                2                50                   0.968                       0.998
                                1                100                  1.111                       1.182

        As indicated, the XP Storm peak discharge results are of the same magnitude as the results initially estimated using the
        Rational Method. It was therefore concluded that the existing XP Storm model was functioning correctly.


4.1.4   Developed Scenario Model


        A developed scenario model was then created with internal catchments and parameters modified from the existing model
        to suit the proposed development as outline in Table 6, 7 and 8.


                                        Table 6: XP Storm Developed Model Parameters – Site A
                                         Parameter                    Site A Catchment
                                                                Pervious Data       Impervious Data
                                 Area (ha)                            -                    3.46
                                 Slope (%)                            -                     1
                                 Mannings ‘n’                         -                   0.015
                                 Initial Loss (mm)                    -                     0
                                 Continuing Loss (mm/hr)              -                     0
                                 Laurenson ‘n’                      -0.285                -0.285


                                     Table 7: XP Storm Developed Model Parameters – Site B (North)
                                          Parameter               Site B Northern Catchment
                                                                Pervious Data       Impervious Data
                                 Area (ha)                            -                    0.25
                                 Slope (%)                            -                     1
                                 Mannings ‘n’                         -                   0.015
                                 Initial Loss (mm)                    -                     0
                                 Continuing Loss (mm/hr)              -                     0
                                 Laurenson ‘n’                      -0.285                -0.285


                                     Table 8: XP Storm Developed Model Parameters – Site B (South)
                                          Parameter               Site B Southern Catchment
                                                                Pervious Data       Impervious Data
                                 Area (ha)                            -                    0.45
                                 Slope (%)                            -                    1.5
                                 Mannings ‘n’                         -                   0.015
                                 Initial Loss (mm)                    -                     0
                                 Continuing Loss (mm/hr)              -                     0
                                 Laurenson ‘n’                      -0.285                -0.285




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