H - Revised Integrated Water Management Plan by Cardno (inc MUSIC file) (13.09.19)

                                                                                    Integrated Water Management Plan
                                                                            Noosa Marketplace : 2-20 HOFMANN DRIVE




5         Stormwater Quantity Management

5.1       Background
Using XP-RAFTS, the hydrological model developed above was modified to represent the proposed
development. The model was then used to determine the effects that the proposed development would have
on the stormwater discharge (peak flow rates) coming from the subject site. It is anticipated that, as a result of
the development, peak flow rates will increase. As such, recommendations will be made to ensure peak flows
from the site are equal to or less than those for existing conditions. Detention storage on site will be achieved
through a proposed detention tank system.

5.2       Model Setup
5.2.1     Catchment Parameters
Catchment parameters for the existing and developed local catchment hydrology are shown in Table 4-1. The
existing scenario is as per the hydrological model described above. The changes made for the developed
scenario involved updating the percentage impervious values to represent the proposed development. These
changes are shown in the table below.
              Local Catchment Parameters
                                    Catchment Parameters Existing vs Developed
                                                      Percentage          Percentage
 Catchment ID                   Area (ha)          Impervious Existing    Impervious         Vectored Slope (%)
                                                           (%)           Developed (%)
 1                                 2.31                    95                 95                     2.96
 2                                 0.77                    95                 95                     5.10
 3                                 0.60                    95                 95                     5.20
 4                                 0.69                    95                 95                     3.36
 5                                 1.17                    50                 95                     3.39
 6                                 0.34                    0                  75                     1.81
 7                                 0.18                    0                  75                     1.22
 8                                 1.15                    95                 95                     1.34
 9                                 0.46                    95                 95                     1.56
 10                                0.88                    50                 50                     1.41
 11                                0.09                    50                 50                     0.31
 12                                0.06                    95                 95                     0.84
 13                                0.14                    5                  95                     1.86
 14                                0.53                    5                  95                     2.07
 15                                0.54                    0                  95                     0.78
 16                                0.16                    5                  20                     0.09
 17                                0.45                    0                  95                     2.48
 18                                0.17                    35                 35                     3.58
 19                                0.14                    0                  100                    1.52
 20                                0.42                    5                  60                     1.28
 21                                1.53                    95                 95                     0.92




V190428 | 10 September 2019 | Commercial in Confidence                                                           13