2019-12-16 GC Agenda - Item 5 - Attachment 1 - Noosa Spit Shoreline Erosion Management Plan-Part 1

 Noosa Spit SEMP Final Report                                                                            25
 Numerical Modelling of Entrance Configurations




3.2.3    Boundary Conditions
         The model is forced by swell wave parameters derived from the Mooloolaba Waverider buoy and
         deep-water wave transformation and applied to the offshore boundary of the 400 m resolution grid.
         Wind wave development was simulated using a spatially and temporally varying wind field. The wind
         boundary condition was derived from the NOAA CFSR and CFSv2 global model datasets (Saha et
         al. 2010; 2014). A temporally varying water level (informed by Mooloolaba tide gauge recordings)
         was applied to the 25 m nest to capture the potential for depth-limited wave conditions within Laguna
         Bay.

3.3      Hydrodynamics (TUFLOW FV)
         The hydrodynamic modelling component has been undertaken using the TUFLOW FV software,
         which is developed and distributed by BMT (https://www.tuflow.com/Tuflow%20FV.aspx). TUFLOW
         FV is a numerical model for the 2D and three-dimensional (3D) Non-Linear Shallow Water Equations
         (NLSWE). The model is suitable for solving a wide range of hydrodynamic systems ranging in scale
         from open channels and floodplains, through estuaries to coasts and oceans.

         The Finite-Volume (FV) numerical scheme employed by TUFLOW FV can solve the NLSWE on both
         structured rectilinear grids and unstructured meshes comprised of triangular and quadrilateral
         elements. The flexible mesh allows for seamless boundary fitting along complex coastlines or open
         channels as well as accurately and efficiently representing complex bathymetries with a minimum
         number of computational elements. The flexible mesh capability is particularly efficient at resolving
         a range of scales in a single model without requiring multiple domain nesting.

3.3.1    Model Domain, Mesh & Bathymetry
         The model domain is shown in Figure 3-2 and extends from Double Island Point in the north to Point
         Cartwright (Mooloolaba) in the south and includes the tidal extent of the Noosa River. The model
         mesh is comprised of 44,632 elements with resolution at the offshore boundary approximately 2 km
         (mesh cell side length), increasing to 20 m in the nearshore coastal and estuarine areas. It is noted
         that higher resolution can be easily added to the model at specific areas of interest and has been
         applied to some areas when neatly resolve specific management actions described in Chapter 4.

         Figure 3-3 shows detail of the model mesh at Noosa Spit with the high-resolution bathymetry survey
         captured by Acoustic Imaging. The hydrodynamic model bathymetry relies on the same bathymetry
         datasets listed in Section 3.2.1.

3.3.2    Model Configuration
         The hydrodynamic modelling described in this report has used a 2D configuration of TUFLOW FV.
         The model has used the following configurations and parameterisations:

         • Smagorinsky model to estimate horizontal turbulent and sub-grid mixing;

         • Bottom drag derived from application of the ‘log-law’; and

         • Bottom roughness length-scales between 0.05-0.5 m, with the lower limit used for sandy areas
           and the upper limit used for mangrove areas.



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