Swmp

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
Headland Drive Road Reserve. Roof runoff from existing dwellings appears to be a mixture of
discharging directly to ground level & via kerb adaptors to Headland Drive.

The total impervious areas have been estimated using the detailed site survey and was found to be
approximately 1521m2 which equates to approximately 22% of Impervious Area for (Cat A) & 41% of
Impervious Area for (Cat B) respectively.

The existing site catchments are as follows.

Catchment A

     -   Area – 0.4833 Ha
     -   Tc – 15 mins
     -   Fraction Impervious (Fi) – 0.21




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