SUPERSEDED NEGOTIATED - OPW25 0042 - REFERENCE DOCUMENT (As Published)

            –   Sensitivity 1 - Increased flow path roughness (005) – The proposed flow path through the development site is currently proposed to
                have a manicured grass base (n=0.035) with vegetated batters (n=0.06). The sensitivity assessment was completed assuming the
                base is also vegetated (n=0.06).

            –   Sensitivity 2 - Blocked Rapid Infiltration Pit (RIP) (005a) – Assumes the catchments on the north side of Serenity Close that report to
                approved on-site RIP’s are blocked with catchments Lot 4, Lot 5, 4A and 4B all report into Serenity Close. Lots 1 and 2 do not report
                to a RIP and would report to Serenity Close as currently does.

            –   Sensitivity 3 - Partially Blocked Rapid Infiltration Pit (RIP) (005b) – Assumes the catchments on the north side of Serenity Close that
                report to approved on-site RIP’s are partially blocked with catchments Lot 4, Lot 5, 4A and 4B all report into Serenity Close. Lots 1
                and 2 do not report to a RIP and would report to Serenity Close as currently does. For this scenario it is assumed that the RIP can
                manage the Q10 with excess flows reporting Serenity Close.

        2.2.1.1 Topography
        Model topography has been based upon 2015 Light Detection and Ranging (LiDAR) along with the detailed site survey. Design DEM has been
        incorporated into the model to represent the proposed development.

        The catchment has been modelled using a 0.5m hydraulic model grid size.

        2.2.1.2 Boundaries
        The inflow boundaries for the catchment have been read into the model using inflow polygons (2d_sa and 2d_bc) to represent inflow from
        the WBNM hydrology model.

        The outflow boundary for the model has been applied 70m downstream of the site, which is approximately 5m lower than the site outlet
        and is considered suitable for this assessment. A normal depth rating curve has been adopted for the downstream with a water surface slope
        of 0.02 m/m.

        2.2.1.3 Roughness
        The model roughness is represented by the Manning’s roughness coefficient, n, in the TUFLOW materials file. Manning’s coefficients have
        been applied to reflect the land use within the catchment, assuming development conditions based on NSC zoning and aerial imagery.
        Roughness coefficients are outlined in Table 2.4, while the spatial distribution of material types in the TUFLOW model extent is included in
        FIGURE 2.3.

        TABLE 2.4: ADOPTED MANNING’S ‘N’ ROUGHNESS

         Land Use                                                               Manning’s ‘n’

         Road                                                                   0.025

         Buildings                                                              0.3

         Vegetated Channel                                                      0.035

         Vegetation                                                             0.06

         Gravel/Grass                                                           0.065

         Dense Vegetation                                                       0.15

         Residential                                                            0.12


        2.2.1.4 Structures
        The stormwater network represented in the hydraulic model aligns with the stormwater plan and long-section developed by Alta Projects
        and are presented in Appendix B:.




DocumentNOOSA
           Set ID:CALILE  I BBNE01676-0001-REP-001-1
                   23806878                                                                                                                          7
Version: 0, Version Date: 01/01/1900