Appendix I - Stormwater Management Plan

                 minimal and the external stormwater network is assumed to have sufficient capacity
                 to accommodate these flows. Refer Appendix F for calculations.


       4.5       100 Year ARI – Contributing Catchment Flows

                 For comparative purposes, analysis of the major 100 year ARI event has been
                 undertaken utilising the Rational Method in accordance with QUDM for the pre and
                 post development scenarios. The parameters for the pre and post development
                 scenarios remain consistent with those utilised for the 10 year ARI analysis
                 respectively.
                 A summary of the 100 year ARI analysis for each scenario is provided as follows.
                 Refer Appendix G for the pre and post development flow calculations for the 100 year
                 ARI rain event.


        4.5.1      Existing Scenario

                 The contributing flow associated with the existing scenario for the 100 year ARI rain
                 event was determined utilising the Rational Method to be 74 l/s. The overland flow
                 currently contributes to the two pits located on Gateway Drive, north of the site.


        4.5.2      Proposed Development Scenario

                 The resultant overland flow for the proposed development scenario has been
                 determined for the 100 year ARI to be 113 l/s utilising the Rational Method. However,
                 considering that the developed scenario will include an internal stormwater network
                 which is required to accommodate flows associated with the 10 year ARI rain event,
                 the overland flow contributing to Gateway Drive will not exceed 44 l/s. Table 4.1
                 outlines the overland flow associated with the 100 year ARI event for the developed
                 scenario.

                 Table 4-1 Overland flow - Post development

                        Qtotal (l/s)        Qpipe (l/s)         Qoverland(l/s)

                             113                69                   44

                 The above comparative assessment demonstrates that the proposed development
                 scenario results in a reduction in overland flow in the catchment i.e. 44 l/s (developed
                 scenario) compared to 74 l/s (existing scenario). Refer to Appendix G for calculation
                 of both scenarios for the major event.
                 As mentioned previously, this assessment has been undertaken on the basis that the
                 recently constructed stormwater network on Gateway Drive on the east side of the
                 site will have sufficient capacity to accommodate flows associated with the
                 development for the 10 year ARI rain event. In this case, the development will result
                 in less overland flow contributing to Gateway Drive through provision of an internal


Mogpropmanagement Pty Ltd                             Page 11                                205-002-002R
Stormwater Management Plan
Noosaville Site