RFI - SWMP.pdf

6.1      Rational Method


To calculate the peak discharges for the site under existing (pre-development) and proposed (post-
development) conditions the rational method has been used in accordance with QUDM 2017.



6.1.1    Design Storms



As defined in the Noosa Plan 2020 stormwater drainage must be designed in accordance with QUDM
2017, therefore the following design storms were adopted: -



         1.     Minor Drainage System      -       10 Year       ARI (Q10 Storm)
         2.     Major Drainage System      -       100 Year      ARI (Q100 Storm)



6.1.2    Rainfall Intensity



Rainfall intensities were obtained from The Australian Bureau of Meteorology. Refer to Appendix F
for the IFD design rainfall intensity.



6.1.3    Time of Concentration



Times of concentration (Tc) were calculated as defined in QUDM 2017. Refer Table 6.1 for Adopted
time of Concentrations and Appendix E for calculations: -



                                         Table 6.1 – Tc Values

                STATE            CATCHMENT A (Tc) (mins)           CATCHMENT B (Tc) (mins)

          Pre Development                      5                              13.00

          Post Development                     5                               5.67




SCG Consulting Engineers                 Page 16                                    SCG Ref: 31131(SWMP)