Response to information request REC13/0095

 No. 55 Lake Macdonald Drive Cooroy Stage 2 Short Duration Culvert
 Calculations for Access for Lots 5, 6, & 7.




Lot 7 Culvert: Catchment A (see Plan 1225-25).


Catchment Area A                     =
                                         1.653 ha


Q 1 00 rainfall event                FCIA     =
                                                        1/360 x 0.94 x 155 x 1.653                     0.67 m3/s


Cross Road culvert, 1 X 900x300 RCBC with outlet control.


Maximum HW                =
                              103.475(upstream side of dwy) 102.875(RCBC invert)
                                                                        -                              =
                                                                                                           0.6m


ke 0.4, A
     =
                 =
                     0.908 x 0.305        =
                                              0.277 sqm, L      =
                                                                     4.88m


de   =
         0.467(QIB)2/3        =
                                  0.467 X (0.51/0.9)2/3         =
                                                                    0.32m


TW       =
             xsect DIS of2/A (see attached PCDrain Calculation sheet)                        =
                                                                                                 0.232m


(de + 0)/2       =
                     (0.32 + 0.305)/2         =
                                                  0.313m


So ho is greater of 0.232 and 0.313                 =
                                                        0.313m


HW       =
             H + ho   -

                       LSo
0.6   =
          H + 0.313       -
                              0.03
H    =
         0.317


From Figure 9A-5 DTMR Road                         Drainage Manual, Q        =
                                                                                 0.51 m3/s


Q 1 00 weir flow                              =
                                                        Q 1 00 flow 0.67 m3Is      -
                                                                                     0.51 m3Is piped
                                                        0.16 m3/s


Weir Q100                          1.7LH3/2             B   =
                                                                6m
0.16                               1.7 x 6 x H312
H                                  (0.16I (1.7 x 6)i/3
                                   0.063m


Adopt weir capacity for a 0100 of 0.67 m3/s with 6m width, 0.063m upstream depth Hand
900x300 RCBC.


Note culvert more than adequate tor Q5 without overtopping as Q5                             =
                                                                                                  0.32 m3/s vs culvert
capacity of 0.51 m3Is.