Reference Document - Site Based Stormwater Management Plan · MCU21/0117.01

                                                            Rational Method Peak Flow Calculations
Job No:            23098                                                                                                                                                    MORGAN CONSULTING
Job Type:          Proposed Townhouse Development                                                                                                                            ENGINEERS PTY LTD
Address:           5 Pearl Street, Cooroy                                                                                                                                1 GREAT GEORGE STREET
Council:           NSC                                                                                                                                                     PADDINGTON QLD 4064


IFD Data:          26.4125 (S),152.9125 (E)                               Minor Storm:      Q10                                                                             Designed:          WB
1
I10                70mm/hr                                                Major Storm:     Q100                                                                                 Checked:       HM

Pre Development                                                                                        Post Development

Time of Concentration

Standard Inlet Time                                                                                    Standard Inlet Time
     Standard Inlet Time                          mins                                                        Standard Inlet Time               5   mins

Sheet Flow (Friends Equation)                                                                          Sheet Flow (Friends Equation)
    Sheet flow length (L)                   57      m                                                        Sheet flow length (L)                    m
           roughness (n)                  0.03             short grass                                             roughness (n)     0.014                  Concrete
              Fall of NSL                 1.89     m                                                                  Fall of NSL     0.29           m
     Slope of Surface (S)                  3.3     %                                                         Slope of Surface (S)                    %
                      total                9.7    mins                                                                        total    0.0          mins
Concentrated Overland Flow                                                                             Concentrated Overland Flow
           Flow distance                      0    m                                                               Flow distance                     m
                 velocity                   0.7   m/s                                                                    velocity            0.7    m/s
                    mins                    0.0   mins                                                                      mins             0.0    mins
   Surface type multiplier                  3.0                                                            Surface type multiplier           4.0
                     total                  0.0   mins                                                                       total           0.0    mins

Total tc                                    9.7   mins                                                                  Total tc             5.0    mins



Runoff Volume Calculations


      Name          Area (ha)        tc              fi     C10                                            Name          Area (ha)      tc             fi    C10
                     0.228                         0.27     0.75                                                          0.228                      0.76    0.85

           Total      0.228         9.7                     0.75                                                Total      0.228       5.0                   0.85

                   Frequency                                                                                            Frequency
      ARI                            Cy             Iy                     Qy                               ARI                         Cy            Iy                 Qy
                     Factor                                A (Ha)                                                         Factor                           A (Ha)
    (years)                       (Fy*C10)        (mm/h)                 (m3/s)                           (years)                    (Fy*C10)       (mm/h)             (m3/s)
                      (Fy)                                                                                                 (Fy)
      3 mth                                                              0.019                             3 mth                                                       0.026
        1             0.800        0.603           99       0.228        0.038                               1             0.800      0.682          120    0.228      0.052
        2             0.850        0.641           111      0.228        0.045                               2             0.850      0.724          135    0.228      0.062
        5             0.950        0.716           150      0.228        0.068                               5             0.950      0.809          183    0.228      0.094
       10             1.000        0.754           174      0.228        0.083                              10             1.000      0.852          215    0.228      0.116
       20             1.050        0.792           199      0.228        0.099                              20             1.050      0.895          245    0.228      0.139
       50             1.150        0.867           228      0.228        0.125                              50             1.150      0.980          285    0.228      0.176
       100            1.200        0.905           251      0.228        0.143                              100            1.200      1.000          315    0.228      0.199




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