2008/0169 Response to information request - 71 Seaview Tce Sunshine Beach · 132008.169

4.4     TIME OF CONCENTRATION

For the pre development site, the time of concentration was calculated utilising Friend's Equation for overland
sheet flow (Equation 4.06, QUDM, 2"d Edition, 2007).


                                   Table 3 - Pre development time of concentration

          Catchment          Overland Sheetfiow Length (m)            Mannings Coefficient             Sheetflow Slope         Tc min


       Pre Development                       43                                0.035                          36%               6.4



For developed catchments, the time of concentration was determined from a standard inlet time (Table 4.06.1,
QUDM, 2nd Edition, 2007)


                                   Table 4 - Post development time of concentration

                                                      Catchment            Tc min


                                                   Post Development          5.0


4.5     RAINFALL INTENSTIES

The rainfall intensities for the Pre and Post Development Scenarios were determined from the IFD chart for the
Noosa Region calculated from AR&R, 1987.


                                               Table 5 - Rainfall Inten ty
        Time of          1 year          2 year        5 year        10 year               20 year            50 year      100 year
      Concentration        ARI             ARI                ARI             ARI                ARI            ARI             ARI
         (mins)          (mm/hr)        (mm/hr)             (mm/hr)        (mm/hr)         (mm/hr)          (mm/hr)       (mm/hr)
           5.0               129             163              201             223                253            291             321

           6.4               117             149              184             203                231            267             294


4.6     FLOWS (UNMITIGATED)

The flow calculated for the Pre and Post Development Scenarios for a range of storm events are shown below.

                                                  Table 6 - Flows (unm      igated)

                                      Qi             Q2         Q5          Q10          Q20            Q50           Q100
                  Scenario
                                    (m3/s)         (m3/s)     (m3/s)       (m3/s)       (m 3/s)        (m3/s)         (m3/s)

            Pre Development          0.048         0.065       0.089        0.103       0.124           0.156         0.180

            Post Development         0.068         0.091       0.125       0.146        0.174           0.212         0.234

             Increase in Flow        0.020         0.026       0.036       0.043        0.050           0.056         0.054




 SITE BASED STORMWATER MANAGEMENT PLAN - Revision D          71 Seaview Terrace Sunshine Beach                                          10