RFI - Attachment 3 - Stormwater Management Plan

     2.2. Existing Drainage Patterns
Surface runoff from the existing site occurs as overland sheet flow following the natural surface contours which
typically drain towards an existing drainage feature within adjacent lots to the east. This watercourse flows from south
to north as indicated by the green dashed line within Figure 2.2 – Existing Site Drainage Characteristics (Queensland
Globe Watercourse Identification Map, 2022) continuing through Lot 1 SP 248288 to the north.
Upstream catchments contributing to the existing watercourse have been identified by yellow polygons on Figure
2.2. Further detail of these catchments is included within the catchment plan in Appendix A.
An existing 1200mm diameter pipe culvert provides passage for the watercourse beneath Carpenters. Based on
Council flood mapping, this culvert will be overtopped as the major drainage system during larger storm events that
exceed the capacity of the stormwater drainage line. This stormwater culvert, as well as other upstream culverts
along the waterway as identified from Council mapping, are indicated by blue arrows below in Figure 2.2.
Downstream of the proposed development the stormwater flows traverse a number of properties for approximately
750m before discharging to Cooroy Creek Creek, a tributary of the Six Mile Creek Left Branch (refer Figure 2.3).

Run-off from Carpenters Road is typically captured in the roadside table drains, which convey stormwater run-off
north to the existing culvert crossing beneath Carpenters Road (south of the proposed development site). The
southern portion or Carpenters Road is discharged as sheet flow across the batter slopes draining towards the
existing watercourse west of the road.




Project number 21020                                                                                    Page 6 of 36
File RECOR Concept Stormwater Management Report - 21020.docx, 2022-09-05
Revision 0


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