13. Appendix I - Integrated Water Mangement Plan

                                                                                   Integrated Water Management Plan
                                                                           Noosa Marketplace : 2-20 HOFMANN DRIVE




6          Hydraulic Analysis

6.1        Introduction
The site is not affected by regional or tidal flooding. The level of Mean High Water Spring Tide (MHWS) in the
nearby Noosa River at Tewantin is RL 0.61 mAHD (Maritime Safety Queensland, 2015). Due to the site being
at a level of approximately RL 9.0 mAHD, only local flows from the surrounding sub-catchments were
considered for this hydraulic investigation.

6.2        Model Setup
To determine the effects of the proposed development, a TUFLOW model was developed. The inputs into the
model are outlined below;
> Hydrological (flow) information;
> Topography (LiDAR);
> Key drainage infrastructure (1D);
> Land uses;
> Key drainage infrastructure; and
> Model boundary conditions.
Flow information for the TUFLOW model was obtained from the hydrological modelling described earlier in this
report.
LIDAR topographical data was obtained from the Department of Natural Resources, Mines and Energy
(DERM), and was used as the key input to represent the existing scenario. This LIDAR data was then modified
in the TUFLOW model using ‘2d-z shapes’ to represent the changes as a result of the development.
Drainage infrastructure details were sourced from Noosa Council’s Enterprise Mapping System. Upgraded
drainage infrastructure was sized and input into the developed scenario hydraulic model.
The boundary conditions for the model consisted of ‘local’ inflows from each of the surrounding sub-
catchments, as described above, as well as a standing tail water level of RL 4.1 mAHD. This water level was
set to ensure that the environmental reserve downstream of the proposed development did not cause unsteady
flow conditions at the point of discharge. A sensitivity analysis of the standing tail water level was conducted
by setting the water level to RL 5.1 mAHD. This analysis found that by raising the standing tail water level, the
maximum flood levels on the site do not increase. This shows that the flooding behaviour on the site is not
sensitive to tail water conditions and as a result the assumed tail water conditions can be deemed adequate.

6.3        Modelled Events
The 39, 20, 10, 5, 2 and 1% AEP events were modelled to assess potential negative impacts on surrounding
properties as a result of the proposed development. An initial existing conditions scenario (E01) was run to
establish the current flood levels. A number of developed scenarios were run to determine the optimum
developed scenario. Scenario D05 was used to simulate the changes resulting from the proposed
development. All events were run with the tail water level set to RL4.1 mAHD, as noted above.

6.4        Results
Results from the hydraulic modelling are presented in the following sections. The flood levels were reviewed
for both the existing and developed scenarios. Results at a number of key locations have been tabulated.
These locations were mainly on the boundary of the subject site and on roadways as shown in Figure 6-1.




V190428 | 15 May 2019 | Commercial in Confidence                                                                20