RFI - stormwater report

Peak flows tabulated in this report represent the peak values extracted from the
modelled range of storm events presented in Table 3-5 (A01).
Table 3-5: Site Developed Scenario WBNM Outlet Peak Flows (A01)
                       Existing Peak Flow    Developed Peak Flow         Change in Peak Flow
                              (m3/s)                (m3/s)                     (m3/s)
        1 year                0.198                 0.254                      0.056
        2 year               0.228                   0.289                     0.061
        5 year               0.319                   0.398                     0.079
       10 year               0.382                   0.484                     0.101
       20 year               0.441                   0.554                     0.113
       50 year               0.513                   0.628                     0.115
      100 year               0.569                   0.693                     0.124

It can be seen that the peak flows have increased to the catchment A01 outlet. This is a
result of the development site increasing the impervious area. It is proposed that the
outlet from the site will be diverted (piped) to the natural waterway approximately 100m
south of the developed site (Refer Figure 3-2 and Figure 3-4). The piped outlet will divert
the change in peak flow from the proposed site (up to 124L/s) in order to prevent
nuisance runoff from affecting downstream private properties and the road reserve.
The change in peak flow diverted from the site has been assessed in relation to the
regional catchment, refer to Sections 3.1.4 and 3.1.6 below.




                             Catchment
                                A01



                                                             Piped
                                                             Outlet
                                                             Diversion
Figure 3-2: Post-Development Change in Peak Flow Diversion




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