Appendix D- Stormwater Management Plan · MCU23/0078

3.2   PROPOSED STORMWATER DRAINAGE

      The following points outline the proposed stormwater infrastructure for the development site:

          −     Minor events from within Site A will be conveyed by an internal stormwater piped network to the existing 600mm
                dia. stormwater pipe at the south-west corner of the development site;

          −     Minor events from within Site B will be conveyed by an internal stormwater piped network to the existing gully
                pits along the private access roadway along the western frontage of the development site;

          −     Major events will be conveyed via overland flow towards and onto the surrounding private access roadways and
                environmental zones as per existing conditions;

          −     Run-off from the remaining un-developed areas of site B will be conveyed via catch drains around the proposed
                development works area to the private access roadway as per existing catchment characteristics;

          −     As there will be an increase to the impervious area as a result of the proposed development, there will be an
                increase to peak stormwater discharge rates from the development site. Based on this, stormwater detention
                measures are required, and three below-ground stormwater detention tanks are proposed across both Sites A
                and B; and

          −     Considering the development works area is greater than 2500m2, stormwater quality treatment measures are
                required for the proposed development as per the State Planning Policy and Noosa Shire Council Planning
                Scheme. Treatment is proposed within the below-ground stormwater tanks.


      Refer to the engineering drawings in Appendix B for further information.


4. STORMWATER QUANTITY ANALYSIS

      Under the Noosa Shire Council Guidelines, several design elements were identified in relation to stormwater management
      issues. Noosa Shire Council must be satisfied that:


          −     The proposed development can be drained;

          −     The stormwater management system can follow the features and functions of the natural drainage system;

          −     The volume, timing, velocity and pollutant load of stormwater has no adverse effect on any surrounding
                properties or receiving waters; and

          −     Suitable provision is made in the design layout to accommodate for major drainage.


      All stormwater discharge will comply with Noosa Shire Council’s Stormwater Management Code with quantity calculations
      completed in accordance with the requirements and methods outlined in the Queensland Urban Drainage Manual
      (QUDM).


4.1   DETAILED HYDRAULIC MODELLING – XP STORM

      A detailed hydrologic and hydraulic analysis using XP Storm software has been undertaken to model the stormwater flow
      characteristics of the site more accurately.


      XP Storm is a hydraulic modelling software tool that utilises detailed hydrograph flow analysis to provide an effective
      representation of urban stormwater systems. Hydrographs are calculated using the Laurenson Method for runoff routing
      in conjunction with the Uniform Loss model for determining catchment losses. XP Storm has been used to demonstrate




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