Stormwater Management Plan

The most critical events for the site’s catchment are compared in Table 5 below.
                                                          Pre-Development Peak Flow                        Post-Development Peak Flow With
                    ARI Year
                                                                         (m3/sec)                                      Detention (m3/sec)
                          2                                                  0.014                                                0.013
                         5                                                   0.018                                                0.016
                         10                                                 0.023                                                 0.018
                         20                                                 0.026                                                 0.020
                        50                                                   0.031                                                0.022
                        100                                                 0.034                                                 0.024
                              Table 5 – Pre- and Post Development Peak Flows (With Detention)

As depicted in the above table, the peak runoff from the developed site does not exceed the peak runoff
from the existing site.

The peak inundation levels in the tank across the range of storm events analysed are listed in Table 6
below.
                    ARI Year                             Inundation Elevation (m AHD)                                Inundation Depth (m)
                          2                                                 28.97                                                  0.27
                         5                                                  29.07                                                  0.37
                         10                                                  29.15                                                 0.45
                         20                                                 29.24                                                  0.54
                        50                                                  29.35                                                  0.65
                        100                                                 29.45                                                  0.75
                                               Table 6 – Detention Tank Inundation Levels

6.3.4 Stormwater Quality Management Strategy

The development does not involve premises 2500 square meters or greater in size therefore the
development does not trigger the water quality requirements of the State Planning Policy July 2017. As a
result, no water quality improvement devices are proposed as part of development.

The residential development on the lot will incorporate ‘best management practice’ such as roof-water
first flush diverters and landscape swales, where possible, to minimize impacts and satisfy water quality
requirements.




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Inspired engineering

22 May 2025
https://mpncnetau.sharepoint.com/sites/Administration/Shared Documents/10000-10999/10200-10299/10256/Report/22-05-25 SWMP_Issue A.docx