Stormwater Management Plan

Good Shepherd Lutheran College                                                                        Odyssey Consulting Group
Proposed Unit Development                                                              Conceptual Stormwater Management Plan
Lot 30 on SP170751                                                                                           Project No: K4277
115 EUMUNDI NOOSA ROAD, NOOSAVILLE

        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




K4277-0002                                            14 March 2018                                                Page 4 of 16