Stormwater Management Plan

GOOD SHEPHERD LUTHERAN COLLEGE                                                                         Odyssey Consulting Group
Lot 30 on SP170751                                                                      Conceptual Stormwater Management Plan
115 Eumundi Noosa Road, Noosaville                                                                            Project No: K4277

         Table 2:       Pre Development Coefficients of Runoff

           Catchment               2               5                     10                      20                100

                A                 0.60           0.67                   0.70                    0.74               0.84


3.2.3 Time of Concentration
         To calculate the time of concentration for the internal catchment the Friends Equation (tc =
                0.333  0.2
         (107nL )/S ) from QUDM has been applied for overland sheet flow with the remaining distance
         calculated as concentrated flow. Please refer to Table 3 for the calculated time of concentration.

         Table 3:       Pre Development Time of Concentration

                                                                                    Time of concentration

                           Catchment        Catchment                                   Concentrated
           Catchment               2                              Overland flow             flow
                            Area (m )       Properties                                                           Total tc
                                                                Friend’s Equation       QUDM Figure
                                                                                           4.09

                                               Open               Horton’s (n) =
                                           Space/parks –               0.045
               A              5,014         Light cover              L = 90 m                  n/a              12.50 min
                                          bushland / poor         Slope = 4.38%
                                            grass cover            t = 12.5 min


3.2.4 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 pre development case using design rainfall intensities from the Bureau of
         Meteorology Rainfall IFD Data System. 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 pre development peak
         flows for the subject site are presented in Table 4.

         Table 4:       Catchment A - Pre Development Internal Catchment Peak Flow Rates
           Average Recurrence
                                           ARI              2              5              10            20             100
           Interval
           Coefficient of Runoff             C            0.60            0.67           0.70           0.74           0.84
           Average Rainfall Intensity
                                             I           114.91         142.10          157.53         178.98        228.29
           (mm/h)
           Area of Catchment (ha)           A            0.501           0.501           0.501         0.501          0.501
                              3
           Peak Flow Rate (m /s)            Q            0.095           0.132           0.154         0.183          0.267


3.3      Post Development

3.3.1 Catchment Definition and Lawful Point of Discharge
         The post development scenario consists of two internal catchments that convey the stormwater to
         the south and west of the site. A will discharge into existing Council stormwater infrastructure on
         Eumundi Noosa Road on the western site boundary. Catchment B will discharge into existing Council
         stormwater infrastructure on Walter Hay Drive on the southern corner of the site. These discharge
         points represents the Lawful Points of Discharge (LPOD) for the site.

         The post development catchment area and lawful point of discharge is shown on the Odyssey
         Consulting Group, Post Development Catchment Plan (Ref: K4277/P006/C) included as Appendix D.




K4277-0002-C                                        05 November 2018                                                Page 4 of 16