RFI - Stormwater Mgm Plan 20169 - SBSMP - Rev 4 (2)

                                                                                         20169 - SBSMP/4
                                                                                                  Page 11




Ground Catchment:
    1. Surface runoff from the ground level hardstand and landscaping areas of the southern
       catchment will be collected by various stormwater pits connected to the internal drainage
       network, where it will be directed to the detention basin located at the southeast corner
       of the site prior to discharge to the Lawful Point of Discharge within Lot 46 and 62 on
       SP132578.

    2. Surface runoff from the ground level hardstand and landscaping areas of the northern
       catchment will be collected by various stormwater pits connected to the internal drainage
       network, where it will be directed to the detention basin located at the northeast corner
       of the site prior to discharge to the Lawful Point of Discharge within Lot 79 on SP138388.

Refer to Appendix F for the Concept Site Levels and Drainage Plan.

5.3 Downstream Pipe Infrastructure Considerations
The existing 225 to 450mm diameter stormwater line traversing the rear of Lots 45, 46 and 62 on
SP132578 and Lots 42-44 on SP144002 and the existing 300mm diameter stormwater line within
the driveway of Lot 79 on SP138388 have been modelled within PC DRAINS to determine their
capacity to take post-development mitigated flows from the development. The subsequent
longitudinal sections and calculations table have been exported from PC DRANS and outlined
within the drainage plans attached in Appendix F.

It was determined from the results of PC DRAINS modelling that the downstream stormwater
drainage infrastructure has capacity to convey up to 67L/s from southern catchment and 120L/s
from the northern catchment of the proposed development. Subsequent XPSTORM detention
modelling has taken this capacity into account.


5.4 XPSTORM Modelling
5.4.1 Intensity Frequency Distribution
The IFD data and temporal patterns used for the XPSTORM modelling has been obtained from the
Bureau of Meteorology for the following coordinates:
       Latitude -26.406
       Longitude 153.050

Refer to Appendix G for a copy of the BOM IFD data table.

5.4.2 Initial and Continuing Losses
Initial and continuing losses were approximated based on the storm losses obtained from ARR Data
Hub for the aforementioned coordinates. Refer to Table 5-4 below for the adopted initial and
continuing losses.
                           Table 5-4 – Adopted Initial and Continuing Losses

                             Designation               Initial Loss    Continuing Loss

                           Impervious Areas                0.0                   0.0
                            Pervious Areas                25.0                   2.5




Site Based Stormwater Management Plan
Proposed Townhouse Development at 99, 101 & 105 Eumundi Noosa Road, Noosaville