Attachment C - Stormwater report

5.           Flooding and Water Quantity Management

5.1.         Introduction
Hydrologic and hydraulic modelling has been undertaken of the site to establish the flow regime and peak
discharges at the outlet of the site to the north. The modelling has been undertaken in XP-SWMM for both
the pre and post development scenarios. The modelling undertaken for this SMP represents the site
catchment only, and does not take into consideration the large catchment of which the site forms a part.

5.2.         Catchments
Due to the flat grades of the site and lack of defined flowpaths, the site has been considered as a single
33.2 ha catchment for the purposes of this modelling

5.3.         Rainfall Intensities
Intensity Frequency Duration (IFD) data for the site has been derived in accordance with Australian Rainfall
and Runoff (ARR) though the use of the AUS-IFD software. The rainfall intensities generated for the site are
shown below in Table 13.
Table 13- IFD Data Applied to Hydrologic Assessment

 Duration                 I1              I2              I5               I10      I20       I50       I100
 (mins)               (mm/hr)         (mm/hr)         (mm/hr)         (mm/hr)     (mm/hr)   (mm/hr)   (mm/hr)

 10                       95             121             151               168     192       223       247

 15                       80             102             127               142     162       188       208

 20                       70              89             111               124     142       165       183

 25                       62              80             100               111     127       148       164

 30                       57              73             91                101     116       135       150

 45                      45.7             58             73                82       94       110       122

 60                      38.9           49.8             63                70       80        94       104

 90                      30.2           38.8            49.4               56       64        75        84

 120                     25.1           32.4            41.6               47.2     55        65        72




Stormwater Management Plan – Lot 1 on SP108094, 305 Lake Macdonald Drive                                       Page 21

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