1714 IWMP_Report_Carramar_Version2 Oct 2018

The model set-up for the post-development scenario is shown in Figure 3, below.. The model structure
has 17 subareas. Subareas 1 to 12 represent areas other than the proposed roofs, whereas subareas 13 to
17 represent the proposed roofs. The runoff volumes from subareas 13 to 17 are conceptually lumped
together before passing through a single conceptual detention volume, before being conjoined with the
sum of the runoffs from subareas 1 to 13.

The corresponding coding of the Urbs catchment file for this post-development scenario can be seen in
Appendix C hereto.



   NORTH
                                                                       1


                                                           13                 14
                                                  3
                                                       VILLA 4             VILLA 3

                                                                      2
   0            SCALE            50 m

                                                       4           5
   STORMWATER CATCHMENT BDY
   FOR PROPOSED EXTENSION
                                                  6



                                                                 DB        OUT


                             7


                        15
                         ENTRY      LANDSCAPED
                                     PODIUM
                8
                                    9
                                                 17
                          16                           10
        11                                   VILLA 2
                          VILLA 1

                                        12
                        COOROY - NOOSA ROAD


Figure 3:    URBS Model Layout For Post-Development Scenario


The pre-development and post-development models shared the same operating parameters – namely, an
alpha parameter of 2.0 and an m parameter of 0.80, with reach factor lengths varying from 1.9 to 2.5 in

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   Brisbane Stormwater Management Pty Ltd Document File: Carramar.Doc