Amended Stormwater Plan · MCU18/0019

SC7440 – Goodchap St, Noosa                                                                                      8




Under the proposed conditions, the site was ‘split’ into three land use catchment nodes; the roofed area,
driveways and ground level uses. The pollutant export parameters utilised were based on the Urban
Residential pollutant loads, refer Tables 3.4 & 3.5. The pollutants have been generated stochastically in the
modelling scenario.


                      Parameter                                                       Value
               Rainfall threshold (mm)                                                 1
             Soil storage capacity (mm)                                               500
              Initial storage (% capacity)                                             10
                 Field capacity (mm)                                                  200
          Infiltration capacity coefficient (a)                                       211
          Infiltration capacity exponent (b)                                           5.0
                  Initial depth (mm)                                                   50
               Daily recharge rate (%)                                                 28
               Daily baseflow rate (%)                                                 27
             Daily deep seepage rate (%)                                               0
                       Table 3.4 – Rainfall-runoff Parameters Adopted (Urban Residential)



                                             TSS Log                  TP Log                         TN Log
 Flow Type      Surface Type
                                      Mean        Std Dev.    Mean        Std Dev.            Mean       Std Dev.
                      Roof             N/A          N/A        N/A             N/A            N/A             N/A
  Baseflow
                  Driveways            1.00         0.34      -0.97            0.31           0.20            0.20
Parameters
                 Ground Level          1.00         0.34      -0.97            0.31           0.20            0.20
                      Roof             1.30         0.39      -0.89            0.31           0.26            0.23
 Stormflow
                  Driveways            2.43         0.39      -0.30            0.31           0.26            0.23
Parameters
                 Ground Level          2.18         0.39      -0.47            0.31           0.26            0.23
                         Table 3.5 – Pollutant Export Values Adopted (Urban Residential)



3.3.3.1 Rainfall Data
Rainfall data for the site was chosen to give the best representation of actual conditions. A time period of
10 years between 1973 and 1983 was selected from the Cooroy Composite station, using a six minute time
step. The Mean Annual Rainfall for this period is 1595mm, and the Mean Annual ET is 1201mm. See
attached Appendix B for details.