Development Application part 7 of 10 Stormwater Management Report - MCU13/0092

                                                                                                                                                                                                            9.
                                                                                                                                                                                                            ,.
                                                                                                                                                              icu           ei! n$utti!lig
                                                                                                                                                              innov;>tion ingenuity inspiration
                                                                                                                                                                                ASN 89106 675 156
                                                                                                                                                                                                            J
                                                                                                                                                                                                            I




4.        Water Quantity

4.1 Predeve/opment Flows


The predevelopment runoff from the site was calculated using the ILSAX method within Watercom Drains. The runoff
was calculated at the outlets at the north western and south western corners of the site and has been summarized in

Table 2 and 3.



4.2 Detention Storage


The detention storage was calculated for Basin 1 and Basin 2 within Watercom DRAINS. The inflow and outflow
hydrographs are shown in Appendix D. The hydrographs clearly show that the runoff entering the system has been
greatly reduced so that in conjunction with the remaining unmitigated flow there is less than the existing amount of
runoff entering the downstream system. The 15 minute duration storm was found to be the worst case scenario.


The hydrographs are for the storms:


Major events:
               AR&R 100 year, 15 minutes storm, Zone 3
               AR&R 50 year, 15 minutes storm, Zone 3


Minor events:
               AR&R 10 year, 15 minutes storm, Zone 3
               AR&R 2 year, 15 minutes storm, Zone 3
               AR&R 1 year, 15 minutes storm, Zone 3


Designed Basin size:
Basin 1 will be an approximately 9.4m long x 6.0m wide x 1.5m deep. The maximum volume will be approximately
85m3.



                         90                                                                                       :




     -


        E
                         80

                         70

                         60   ..   -- ...
                                            ..




                                            -.
                                                 tl   I
                                                          .
                                                           --




                                                           ..........
                                                                        c   ..-.-
                                                                                      I


                                                                                    ...-L.
                                                                                      !;
                                                                                          ..




                                                                                           -
                                                                                                 ..




                                                                                                 .....
                                                                                                       --




                                                                                                  --<----




                                                                                                             .~.__
                                                                                                                  ;



                                                                                                                  -
                                                                                                                      .-.




                                                                                                                        .__
                                                                                                                            ...        i.


                                                                                                                               ..._.L.._.
                                                                                                                                                                                 ;


                                                                                                                                                          ,
        :::J
                         50                                                          -t                                                                                     ____,---




     -
        o
                         40                                                                                                 .__.   ~
                                                                                                                                       -f-.-              l",          --       <---        --




        (I)                                                                                                                                               I
        E
        :::J
                         30                                                                                   .;...-.
                                                                                           ..-........-.... .-.




                                                                                                                        ...........---t-.............-......i...-.-.-- ...-..-.....!..---.-...--.........
                                                                                                                       --




                                                                                                                                                          I
                         20                                                                                                                                                     +-._---
        o
     >
                         10

                                                                                                                                                          I
                          o
                           1.8                   8                 8.2               8.4                    8.6                    8.8                    9                   9.2                    9.4


                                                                                          Elevation (m)

                                                                        Figure 3: Volume vs Elevation for Basin 1
                                                                                    Page 18

Level Z, 39 Sherwood Road                                                   [email protected]                                                                                 P: 07 3870 8888
Toowong QLD 4066                                                        www.         ubed.com.au                                                                               F: 07 3870 8988