SWMP change reps

package PC DRAINS.          Modelling has established existing and proposed stormwater drainage
characteristics. This includes a climate change rainfall multiplier of 1.2 (20%)

Rainfall patterns accompanied with Initial Loss (IL) and Continuing Loss (CL) was sourced from the
Australian Rainfall and Runoff 2019 (ARR 2019) data hub for Noosaville.

Initial Losses (IL) and Continuing Loss (CL) were approximated based on the storm losses from the
ARR Data Hub, Table 6.1 below states the adopted values: -

                                  Table 6.1 - Adopted (IL) and (CL) Values

                                     AREAS               (IL)        (CL)
                                                        (mm)       (mm/hr)

                                   Impervious             1            0

                                     Pervious             27          2.6

Design ARR 2019 storms for Noosaville have been added into DRAINS accompanied with IFD rainfall
depths from the Bureau of Meteorology (BOM) website.

6.1.1    Existing Catchments
The existing site has been divided into two sub catchments to compare the existing site discharge
locations. These are labelled as A & B and are detailed on SCG drawing No. 33132 - SW1.4(Appendix
D)



Times of concentration (Tc) were calculated as defined in QUDM 2017 using a combination of standard
inlet time & overland sheet flow time. Table 6.2 displays the Adopted time of Concentrations.

                                           Table 6.2 – Tc Values

               STATE              Catchment A (Tc) (mins)              Catchment B (Tc) (mins)

         Pre Development                      15                                   13

         Post Development                       6                                  6



6.1.2    Existing Site
The existing site consists of 4 Lots containing a residential dwelling on each, detached sheds &
landscaped ground areas. The existing surface on Lots 75,76 & part of 77 RP71151 generally falls in an
eastern direction towards the rear boundary & the existing inter-allotment drainage system. Lot 6
SP208257 and a portion of Lot 77 RP71151 generally falls in a south-eastern direction towards the

SCG Consulting Engineers                   Page 16                             SCG Ref: 33132(SWMP).RevC