Response to information request REC13/0095

  Lot 6 Culvert: Catchment A + B (see Plan 1225-25).


  Catchment Area A                  =
                                        1.755 ha


 Q 1 00 rainfall event              FCIA       =
                                                         1/360 x 0.94 x 155 x 1.755              =
                                                                                                           0.711 m3/s


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


 Maximum HW                =
                               1 02.883(upstream side of dwy)            -
                                                                              1 02.364(RCBC invert)        =
                                                                                                               0.519m


 ke=O.4, A        =
                      0.908 x 0.305        =
                                               0.277 sqm,L       =
                                                                      4.88m


 de   =
          0.467(QlBi/3         =
                                   OA67 X (OAI0.9i/3         =
                                                                 0.272m


 TW       =
              xsect D/S of2/C (see attached PCDrain Calculation sheet) = OA11m



 (de + D)/2       =
                      (0.272+ 0.305)/2          =
                                                    0.288m


 So ho is greater of 0.411 and 0.288                 =
                                                         0.411m


 HW       =
              H + ho   -

                           LSo
 0.519     =
               H + 0.411       -
                                   0.064
 H    =
          0.172


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


Q 1 00 weir flow                                         Q100 flow 0.711 m3/s         -
                                                                                        0.40 m3/s piped
                                                         0.311 m3/s


Weir QIOO                           1.7LH312             B   =
                                                                 3m
0.311                               l.7 x 3 x H312
H                                   (0.3111(1.7 x 3))2/3
                                    0.155m


Adopt weir capacity for a 0100 of 0.711 m3/s with 3m width, 0.155m upstream depth H and
900x300 RCBC.


Note culvert more than adequate for Q5 without overtopping as Q5                                =
                                                                                                    0.34 m3/s vs culvert
capacity of 0.40 m3/s.




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flooding calcs.doc