16-001014-02A (Ultimate SCMMP)

Central Bioretention Basin
Critical Section
CROSS SECTION DETAILS                                                      10% AEP                             1% AEP
     POINT       CH                    Z             n              wA       wP        n x wA         wA         wP      n x wA




                   1           ‐4.2   100.95      0.060
                   2           ‐4.2   100.35      0.060             0.00        0.04    0.00          0.00      0.09      0.00
                   3             ‐3   100.05      0.060             0.23        1.24    0.01          0.29      1.24      0.02
                   4              3   100.05      0.060             2.06        6.00    0.12          2.36      6.00      0.14
                   5            6.6   100.95      0.060             0.24        1.42    0.01          0.31      1.62      0.02




                                                                   wA         wP        n x wA     wA       wP           n x wA
                                                TOTAL           2.533472    8.69928    0.152008 2.958498 8.950312        0.17751
                            S
                          0.005                                     R           n        Q              R         n        Q
                                                                0.291228      0.060     1.31        0.330547    0.060     1.67
                                                       Flow                    1.31                              1.67

                                                      WSL                   100.394                            100.443

                       Calculated by Manning's Equation                         1.31                            1.67
                                               Vel (m/s)                        0.52                            0.56

                                                              Basin Section
                                                         101

                                                     100.9

                                                     100.8

                                                     100.7
  Height (m AHD)




                                                     100.6

                                                     100.5

                                                     100.4

                                                     100.3

                                                     100.2

                                                     100.1

                                                         100
           -6             -4               -2                   0                2              4               6            8
                                                                    Width (m)

                                                Existing Sur face          10 % AEP       1% A EP



As indicated in results above velocities are only slightly above 0.5m/s (by 0.02m/s and 0.06m/s
during the major storm). This is within the requirements for the major storm (less than 2m/s) but
only slightly above for the minor storm. However, scour or damage of vegetation is unlikely as the
results do not take into account the backflow effect caused by the outlet pit and weir which will
reduce velocities through the basin. Therefore the design of the basin is appropriate to cater for
inflow velocity.