Swmp

                                    Table 6.3 – Existing Site Peak Flow Rates (L/s)

  Storm Event          Q1            Q2              Q5             Q10           Q20           Q50       Q100
                     (1EY)         (0.5EY)       (0.5EY)       (10%AEP)       (5%AEP)      (2%AEP)      (1%AEP)


 Existing PFR          111           160             216            251           295           352           391

 (PFR – Peak Flow Rate)

6.1.2     Proposed Site
The development consists of the construction of residential townhouse/ unit development along with a
shared access driveway and ground level landscaping/ courtyards & a community pool area. The total
pervious area for the site was calculated to be approximately 1330m2 which equates to a fraction
impervious of 0.79.

The Developed site catchment is as follows.

    -    Area – 0.6326 Ha
    -    Tc – 6 mins
    -    Fraction Impervious (Fi) – 0.79

Peak flow rates for the median design storms for the developed site are given in Table 6.4

                                   Table 6.4 – Developed Site Peak Flow Rates (L/s)

  Storm Event          Q1            Q2               Q5            Q10           Q20           Q50       Q100
                     (1EY)         (0.5EY)          (0.2EY)    (10%AEP)       (5%AEP)      (2%AEP)      (1%AEP)

 Developed             184           232             286            347           399           468           523
 PFR

(PFR – Peak Flow Rate)

6.1.3     Peak Flow Comparison
Table 6.5 indicates the increased peak flow rates for the developed cases.

                           Table 6.5 – Comparison of Existing Vs Developed Peak Flows (L/s)

        AEP            Q1          Q2          Q5             Q10           Q20           Q50          Q100
        Storm        (1EY)      (0.5EY)      (0.2EY)       (10%AEP)       (5%AEP)       (2%AEP)       (1%AEP)

        Increase       73          72          70             96            104           116           132
           PF
   (PF – Peak Flow )



SCG Consulting Engineers                        Page 16                                       SCG Ref: 33132(SWMP)