Stormwater Management Plan · MCU18/0019

SC7440 – Goodchap St, Noosa                                                                            11




4.3.2   Catchment Areas
The subject site has been modelled in its existing pre-development and proposed post-development states
with the catchment areas illustrated in Tables 4.1 & 4.2 and Appendix A. In its pre-development state the
subject site was modelled as one hydrologic node to replicate the existing sheet flow situation for the lot.
XP-STORM model outputs are included in Appendix C of this report.


                 Node                     Description              % Impervious      Area (Ha)

                                           Landscape                      0             0.512
                 ‘PRE’
                                              Roof                      100             0.162

                              Total Catchment (ha)                       24             0.674
                         Table 4.1 - Pre Development Node Sub-Catchment Areas


                 Node                      Description            % Impervious       Area (Ha)
                ‘TANK’                        Roof                     100             0.400
                                     Carpark/hardstand areas           100             0.085
                                           Landscape                    0              0.189
                          Total Catchment (ha)                          72             0.674
                          Table 4.2 - Post Development Sub–Catchment Areas

4.3.3   Roughness Coefficients
The conduits and links used within the model are based on the ultimate design scenario for the internal
roadways and overland flow paths. Mannings “n” roughness coefficient values are specified as 0.014 for
RCP pipes and 0.011 for uPVC pipes.


For overland flow within the sub-catchment areas a Mannings “n” value of 0.014 for concrete areas and
0.045 for vegetated areas was adopted.


4.3.4   Storm Events
Storm patterns were setup using Australian Rainfall and Runoff storm patterns for Area 3 with intensity
frequency duration data taken for the local area. Storm durations of 10, 15, 20, 25, 30, 45, 60 and 90
minutes were investigated for the pre and post developed scenarios.