Cardno Amended flood report July 2018

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. Plate 4-2 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 Plate 4-2. 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. Table 4-1
summarises the variety of land-uses present in the catchment and adopted hydraulic
roughness parameters assumed for each.

Table 4-1 Manning’s n Roughness Values

           Land Use                        Manning’s ‘n’


             Roads                             0.02
           Golf course                         0.03
        Dense Vegetation                       0.12
           Easements                           0.06
             Urban                              0.2
            Buildings                           0.5



4.1.5      Cross-sections
Cross-sections from the flood study undertaken in 2006 have been used in defining Wooroi
Creek and the tributary to the east of the study site. From a comparison of the LiDAR data
against the cross sections, modification of the 2D grid was undertaken to reflect the bottom
level of the cross sections.
4.1.6      Dam
A dam is located on the tributary near the downstream boundary of the site. From the survey
data, the main dam embankment is graded from 8.2 mAHD to 8.0 mAHD, with the spillway
level at 7.53 mAHD. The dam has been modelled using these levels.
4.1.7      Road Levels
The LiDAR data obtained for the study agreed well with the levels used in the 2006 study.
4.1.8      Structures
Dimensions of key hydraulic structures have been obtained from the Noosa Council
Interactive Mapping website. These have been represented using 1D elements in the
hydraulic model. The location of structures is shown in Plate 4-2.