Approved Plans - MCU18-0097 · MCU18/0097

                 GOOD SHEPHERD LUTHERAN COLLEGE                                                                        ODYSSEY CONSULTING GROUP
                 Lot 30 on SP170751                                                                         Conceptual Stormwater Management Plan
                 115 Eumundi Noosa Road, Noosaville                                                                               Project No: K4277

                          Coefficient of Runoff
                          The post development coefficient of runoff (C year) was determined based on the fraction impervious
                          (fi) method as specified in QUDM. Using a one hour, ten year rainfall intensity (1I10) of 72.3 mm/hr, the
                          following coefficient of impervious (C10) values have been adopted for the post development
                          scenario.

                          Table 5:       Post Development Catchment Impervious Properties

                            Catchment     Impervious Area (m2)         Catchment Area (m2)          Fraction Impervious                 C10
                                 A                  3092                       3,878                       0.80                         0.86
                                 B                   592                        889                        0.67                         0.83
                                 C                    0                         247                        0.00                         0.70

                          With reference to QUDM Table 4.5.2, by applying the frequency factors for the standard storms of 2,
                          5, 10, 20, 50 and 100 years result in the following post development coefficients of runoff as shown in
                          Table 6.

                          Table 6:       Post Development Coefficients of Runoff

                            Catchment               2                    5                    10                     20                   100

                                 A               0.73                  0.82                  0.86                   0.90                  1.00
                                 B               0.71                  0.79                  0.83                   0.87                  1.00
                                 C               0.60                  0.67                  0.70                   0.74                  0.84


                          Time of Concentration
                          Post development catchments A & B consist of paved areas and have therefore been assumed to have
                          a standard time of concentration of five (5) minutes as per T.4.6.2 – Recommended standard inlet
                          time. The time of concentration for Catchment C is indicated below in Table 7.

                          Table 7:       Catchment C Time of Concentration

                                                                                                      Time of concentration
                                          Catchment          Catchment
                            Catchment                                                 Overland flow           Concentrated flow
                                           Area (m2)         Properties                                                                        Total tc
                                                                                  Friend’s Equation           QUDM Figure 4.09
                                                                                 Horton’s (n) = 0.035
                                                             Light cover
                                                                                       L=5m
                                 C            247          bushland / poor                                                n/a                  5 min
                                                                                     Slope = 6%
                                                             grass cover
                                                                                     t = 4.5min

                          Design Flow Rates
                          Design storm flow rates have been calculated for standard storms with an ARI of 2, 5, 10, 20, 50 and
                          100 years for the post development case using design rainfall intensities from the Bureau of
                          Meteorology. The Rational Method (Q = 2.78 x 10-3 CIA) has been used to calculate the required
                          design flow rates for the subject site. The calculated post development peak flows for Catchment A, B
                          and C are presented in Table 8, 9 and 10 respectively.

                          Table 8:       Catchment A Post Development Peak Flow Rates
                            Average Recurrence Interval          ARI             2              5             10                 20             100
                            Coefficient of Runoff                 C             0.73           0.82          0.86               0.90            1.00
                            Average Rainfall Intensity
                                                                  I             164            202            223               253             321
                            (mm/h)
                            Area of Catchment (ha)                A            0.388          0.388          0.388              0.388          0.388
                            Peak Flow Rate (m3/s)                 Q            0.129          0.178          0.207              0.246          0.346




                 K4277-0002-E                                                 18 June 2019                                                Page 5 of 14
Document Set ID: 20894174
Version: 1, Version Date: 03/07/2019