Updated SWMP

     f)              The 10% AEP capacity of the road is as per the approved matches the approved SMP for the
                     adjacent developments at 25 Pavilion St, which states:
                     “Existing drainage capacity of Pavilion Street is approximately equivalent to the 10% AEP storm event,
                     with flow greater than this overtopping the verge and entering the site.”
                     This has intentionally been kept consistent between SMPs, and demonstrates that the proposed
                     augmented basin achieves greater storage and improved freeboard in comparison to the
                     approved SMP for 25 Pavilion St.
                     A road capacity calculation was completed to confirm this assumption using a cross section of the
                     road based on LIDAR data. Refer to Table 1-2 and Figure 1-5. Manning’s equation indicates that the
                     road has a road capacity (1.16 m3/s) greater than the 10% AEP flow rate from the external
                     catchments (0.437 m3/s for EX1 and 0.165 m3/s for EX2). Therefore, the assumption that Pavilion St has
                     capacity for 10% AEP flows is conservative, and freeboard within the basin is expected to be greater
                     than modelled.

Table 1-2: Pavilion St Road capacity calculation using Manning’s’ equation
                            Parameter                                Value                            Unit
                     Cross sectional area                            1.24                              m2
                        Channel slope                                0.026                            m/m
                      Wetter perimeter                               11.21                             m
                        Manning's (n)                                0.04
                     Hydraulic radius (R)                             0.1                              m
                             Velocity                                0.93                             m/s
                       Froude Number                                 0.73
                        Flow rate (Q)                                1.16                             m3/s




                                                             Road Cross Section
                      0.2
                     0.18
                     0.16
                     0.14
                     0.12
     Elevation (m)




                      0.1
                     0.08
                     0.06
                     0.04
                     0.02
                        0
                             0              2            4                  6          8             10                12
                                                                                                       Ground Level
                                                      Distance (m)
                                                                                                       Water level


Figure 1-5: Pavilion St Road Cross-Section




23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona                                             Page 17