8. Volume 5 - Stormwater Management Plan

                                             LAMBERT & REHBEIN
                                               ENGINEERS • MANAGERS • SCIENTISTS


                           Table 5 Post Development Peak Flow Rates
  ARI (Years)       Rational Method (m3/s)   XPStorm (m3/s)      Difference (m3/s)     Difference (%)

      Q1                    0.061                0.080               + 0.019                + 31%

      Q2                    0.083                0.103               + 0.020                + 24%

      Q5                    0.114                0.129               + 0.015                + 13%

      Q10                   0.132                0.143               + 0.011                + 8%

      Q20                   0.158                0.164               + 0.006                + 4%

      Q50                   0.196                0.178               - 0.018                 - 9%

     Q100                   0.216                0.199               - 0.017                 - 8%


The order of magnitude of the XPStorm Model results correlate reasonably well for all intensity
events when compared with the rational method calculations.

Table 6 below compares the XPStorm model results of the pre development peak flows and the
post development unmitigated peak flows.
                         Table 6 XPStorm Peak Flow Rates Comparison
                    XPStorm Post Development        XPStorm Pre            Increase         Increase
  ARI (Years)
                        Unmitigated (m3/s)       Development (m3/s)          (m3/s)            (%)

      Q1                      0.080                      0.047             + 0.033           + 70%

      Q2                      0.103                      0.079             + 0.024           + 30%

      Q5                      0.129                      0.112             + 0.017           + 15%

      Q10                     0.143                      0.128             + 0.015           + 12%

      Q20                     0.164                      0.150             + 0.014            + 9%

      Q50                     0.178                      0.162             + 0.016           + 10%

     Q100                     0.199                      0.180             + 0.019           + 11%




 Ref: B16239CR002                                        - 7 -                           Stormwater Management Plan
                                                                                      Noosa Energy Centre - Noosaville