Appendix F - Flood Study

                                                                                                    Flood Study
                                                                                          Noosa Care - Carramar



3.1.1          RORB Parameters
A full range of rainfall event durations has been run for the 10% and 1% AEP climate change events. This was
to ensure that the peak event was captured for the inflow into the hydraulic model.
An initial and continuing loss approach was adopted to represent the expected losses from the design storm
events. An initial loss of 15.0 mm and a continuing loss of 2.5 mm/hr were adopted. The parameters adopted
for this study are provided in Table 3-1, which has been validated using the Rational Method.
The AR&R 2016 Intensity Frequency Duration (IFD) data was used to define the rainfall intensities for use in
the hydrology model. To account for the impact of climate change the rainfall intensities were increased by 20
percent.

3.1.2          RORB Validation
As there was no stream flow gauge within the catchment, there was no opportunity to calibrate the rainfall and
runoff model (RORB) using known flow hydrographs and rainfall.
Validation of the RORB model was undertaken using the Rational Method at the outlet point of the catchment.
The Bransby-Williams method was used to calculate the time of concentration.
Table 3-1 below shows the Rational Method parameters adopted, with validation results presented in
Table 3-2. The C10 values adopted are in line with the parameters used in the 2006 flood study.

Table 3-1      Rational Method Parameters
                                    Total Catchment
 Catchment Area (ha)                      503
 Fraction Impervious                      0.24
 Runoff Coefficient (C10)                 0.76
 Time of Concentration (min)              77.5




24 July 2017                                       Cardno                                                    6