21-0288-FS001-V4_GlenridgeDr_FS-reduced

      4. HYDRAULICS
      Hydraulic modelling has been carried out using TUFLOW software developed by BMT WBM.
      TUFLOW is a computational engine that provides one-dimensional (1D) and two-dimensional
      (2D) solutions for the free-surface flow equations to simulate flood and tidal wave
      propagation. The Heavily Parallelised Compute (HPC) computational method has been
      applied using 2020-10-AA version of TUFLOW. Modelling assumptions and outcomes are
      described below.

              Model Setup
      4.1.1. Topography

      TUFLOW model topography is based upon the DEM that was created from 2015 LiDAR and
      detailed site survey. The catchment has been represented using a 5m hydraulic grid size.
      The internal road was represented the proposed road profile using a 2d_zsh, with the crown
      having a minimum level of 12.81m AHD above the culvert.
      The building envelopes were also raised to ensure flood immunity using a 2d_zsh, with minor
      regrading of lot beside building envelope of Lot 1.

      4.1.2. Inflow

      Inflows have been incorporated into the model setup using inflow polygons (2d_sa) to read
      in the inflow hydrographs from the WBNM hydrology model.

      4.1.3. Roughness

      The roughness of the flow path has been incorporated into the model using Manning’s ‘n’
      values to represent the differing land-uses. Table 4-1 outlines the applied roughness values.
      Table 4-1: Model Roughness Values
                  Description                                   Manning’s ‘n’
                    Road                                           0.015
                 Road Reserve                                      0.03
        Cleared / Sporadic Vegetation                              0.04
            Low Dense Vegetation                                   0.06
           Highly Dense Vegetation                                 0.10


      4.1.4. Boundary

      The TUFLOW model has been extended 1.5 km downstream of the study area such that tail
      water assumptions do not influence flooding at the site. A normal depth rating curve has
      been adopted for the downstream.

      4.1.5. Culverts
      A total of eighteen (18) existing culverts were represented within the model extent, with
      culvert information obtained from Noosa Shire Council GIS information. The new ‘internal’
      culvert has been sized to ensure the internal road servicing the development can achieve
      immunity in the 10% AEP and remain trafficable in the 1% (2100) AEP event. A summary of
      the culverts represented in the model are detailed in Table 4-2.




21-0288-FS001-V4 | Flood Investigation | 60 Glenridge Drive, Cooroibah                                | 10