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

                          Table 9:       Catchment B Post Development Peak Flow Rates
                            Average Recurrence Interval         ARI            2             5              10              20         100
                            Coefficient of Runoff                C            0.71         0.79            0.83          0.87          1.00
                            Average Rainfall Intensity
                                                                 I            164           202            223           253           321
                            (mm/h)
                            Area of Catchment (ha)               A           0.089         0.089          0.089          0.089        0.089
                            Peak Flow Rate (m3/s)                Q           0.029         0.039          0.046          0.054        0.079


                          Table 10:      Catchment C Post Development Flow Rates
                            Average Recurrence Interval         ARI            2             5              10              20         100
                            Coefficient of Runoff                C            0.60         0.67            0.70          0.74          0.84
                            Average Rainfall Intensity
                                                                 I            164           202            223           253           321
                            (mm/h)
                            Area of Catchment (ha)               A           0.025         0.025          0.025          0.025        0.025
                            Peak Flow Rate (m3/s)                Q           0.007         0.009          0.011          0.013        0.018


                 3.4      External Catchments
                          The subject site and the surrounding area were examined to determine if any external catchments
                          will contribute to the subjected site. The size of external catchments has been determined based on
                          ground contours, existing roads and existing stormwater infrastructure. An external catchment has
                          been identified to the North of the subject site. The external catchment has been analysed to ensure
                          drainage has been sufficiently sized to convey external flows.

                          The rational method has been utilised to calculate the peak flow rates. The parameters adopted in the
                          rational method have been selected to reflect the current use of the external catchment.

                          Catchment Definition
                          One external catchment has been considered for analysis. External Catchment A has an area of 449
                          m² and currently discharges stormwater along the northern boundary of the subject site.

                          The external catchment is shown on the Odyssey Consulting Group, External Catchment Plan (Ref:
                          K4277/P011/C) included as Appendix E.

                          Coefficient of Runoff
                          The coefficient of runoff (Cy) was determined based on the fraction impervious (fi) method as
                          specified in QUDM. A fraction impervious value of 0.10 has been adopted in accordance with QUDM,
                          Table 4.5.1 Fraction impervious vs development category. The adopted fraction impervious value
                          reflects the potential fully developed future land use. Using a one hour, ten year rainfall intensity (1I10)
                          of 72.3 mm/hr, a C10 value of 0.70 has been adopted for External Catchment A.

                          Time of Concentration
                          To calculate the time of concentration for the external catchment the Friends Equation (tc =
                          (107nL0.333)/S0.2) from QUDM has been applied for overland sheet flow with the remaining distance
                          calculated as concentrated flow. Please refer to Table 11 below for the calculated time of
                          concentration.

                          Table 11:      External Catchment C
                                                                                                    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 = 31 m
                                 A            449         bushland / poor                                          n/a                11 min
                                                                                 Slope = 4.38%
                                                            grass cover
                                                                                  t = 11.04 min


                 K4277-0002-E                                               18 June 2019                                            Page 6 of 14
Document Set ID: 20894174
Version: 1, Version Date: 03/07/2019