Sealed Judgement

    3.5            Modelling Results
    The performance of the detention system was assessed in terms of detention storage depth and Site
    discharge, as discussed in the following sections.
    The assessment considered a range of events up to and including the 1% AEP event including climate
    change. In each case, a range of storm durations between 15 minutes and 4.5 hours was considered
    in order that the storm durations producing peak conditions for the pre-development and post-
    development cases were captured.


    3.5.1          Detention Storage Depth

    Table 3-7 presents the results of the assessment in terms of the maximum detention storage depth
    for each event modelled together with the storm duration producing the maximum depth. The table
    demonstrates that the storage depth is not greater than the maximum detention depths nominated
    in Table 3-6.
    Table 3-7    1% AEP Peak Depth and Critical Durations within Modelled Detention

Detention                                    Peak Storage Depth (m) for AEP

                                                                                                 1% +
                         50%        20%         10%          5%           2%          1%        Climate
                                                                                                Change

A1_Rainwater tank        0.57        0.75        0.86         0.93        0.94        0.94        0.97
                       (25min)     (25min)     (25min)      (25min)     (25min)     (25min)     (25min)

A_Rainwater tank         0.76        0.92        0.94         0.94        0.95        0.95        0.98
                       (25min)     (25min)     (25min)      (25min)     (25min)     (25min)     (25min)

Carpark tank             0.32       0.45        0.46         0.47         0.48        0.48        0.50
                       (180min)   (180min)    (180min)     (180min)     (180min)    (25min)     (60min)


    3.5.2          Site Discharge

    The peak discharge from the site for the pre-development and post-development cases (i.e., sub-
    catchments A+A1) are presented in Table 3-8. The results demonstrate that the peak discharges
    under the post-development scenario (incorporating detention tanks) are not greater than those
    under the pre-development condition.
    Table 3-8    Peak Discharge from Site (Sub-catchments A+A1)

     ARI Event                                           Peak Discharge (m3/s)

                                       Pre-development                     Post-development
                                                                      Incorporating Detention Tank

     50%                                      0.101                                0.070
                                             (60min)                               (60min)

     20%                                      0.154                                0.104
                                             (60min)                               (60min)

     10%                                      0.182                                0.120
                                             (60min)                               (60min)

     5%                                       0.218                                0.146
                                             (60min)                               (25min)

     2%                                       0.248                                0.158




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