Appendix F - Flood Study

                                                                                                       Flood Study
                                                                                             Noosa Care - Carramar




4              Hydraulic Model
The 1D2D modelling system, TUFLOW, was used to compute the channel/river and overland flow components
of the flood study. TUFLOW is a suite of advanced numerical engines and supporting tools used for simulating
free-surface water flow for urban waterways, rivers, floodplains, estuaries and coastlines. The TUFLOW
engines are widely adopted, proving industry leaders in solving all hydrodynamic process using 1D, 2D and
3D solutions.
The hydraulic model consists of two main hydraulic components:
         Key structures (1D); and
         2D grid of the surface topography (including roads and the dam).
A summary of the model elements and inputs is as follows:
         Key crossings have been represented in the 1D TUFLOW modelling.
         Overland flow paths have been represented in the 2D TUFLOW modelling.
         Model Boundary conditions:
               o   Flow hydrographs derived within the hydrological RORB model have been extracted and
                   incorporated into the hydraulic model as appropriate boundary conditions;
               o   The downstream boundary has been modelled as a Head vs Flow relationship.

4.1            Model Setup
4.1.1          Grid Cell Size
The hydraulic model topographical grid is a key component of the model and was constructed from the DEM
(Section 2.1). A grid cell size of 4 m was adopted for the model area.
This size was considered a fine enough resolution to appropriately define topographical features such as roads
and open drains whilst remaining computationally efficient.

4.1.2          Model Extent
The hydraulic model has been extended upstream of the site to allow for flood storage on the southern side of
Cooroy-Noosa Road. Figure 4-1 shows the model extent.

4.1.3          Inflows
Inflows have been incorporated into the TUFLOW model as Flow/Time dependent 2D boundary conditions.
The locations of the 2D inflow locations into the model are illustrated in Figure 4-1. The inflows were generated
using a RORB model of the catchment (Section 2.1). Inflows for the tributary were located upstream of Cooroy-
Noosa Road, so that the storage provided by this crossing could be properly accounted for.

4.1.4          Roughness
Within the hydraulic model, a Manning’s ‘n’ parameter was used to describe the hydraulic roughness. The
hydraulic roughness for the overland flow model was described using a two-dimensional map of Manning’s 'n'
values. This was developed by digitising different land-use zones from the aerial photography and cadastre
within a GIS environment. Error! Reference source not found. summarises the variety of land-uses present
in the catchment and adopted hydraulic roughness parameters assumed for each.




24 July 2017                                         Cardno                                                     8