2008/0169 Response to information request - 71 Seaview Tce Sunshine Beach · 132008.169

3.7   MANAGEMENT OF FLOWS

To control surface runoff from the adjoining upstream properties it is proposed to construct a concrete/vegetated
trapezoidal drain along the western boundary of the site. The drain will collect all flows (including Qloo) from the
upstream properties. Captured stormwater will be conveyed in a north-westerly direction parallel to the driveway
(and western property boundary). Outfall will occur via a constructed outlet arrangement with rock scour
protection located within the north western corner of the site. Five openings in the northern boundary fence will
direct flows from the trapezoidal channel to the natural gully downstream of the site. The openings will be spaced
apart evenly further reducing flow concentration.


The location of the drain is shown below in Figure 4.




                                                                                     5 FVFNI Y SPACED CUT OUTS IN
                                                                                     BOUNDARY FENCE TO Al LOW
                                                                                     DISCHARGE OF RUNOFF FROM SITE




                                                                                   OULTET LOCATION




                                               Figure 4 - Location of Drain


It is proposed to implement four 600mm x 600mm grated inlets (raised 100mm to minimise blockage) to collect
runoff from the upstream properties and convey flow via a 450mm diameter RCP (minimum grade 1%) to the
north-western corner of the site. The open drain has been sized to convey the entire Qloo storm event in the
highly improbable scenario that the underground stormwater system is completely blocked. The drain will have a
relatively flat gradient of between 2-4%. Couch turf lining of the drain would be adequate to ensure runoff
velocities are below surface treatment design velocities for scour protection. Qloo flow velocities within the
channel would not exceed 1.5m/sec with a couch turf lining (refer to Appendix C for detailed channel
calculations). The drain however is to be a combination of vegetation, concrete and rock check dams. This
proposal will further reduce velocity and scour within the drain during minor and major storm events. A continual
longitudinal plan and section for the drain is not considered necessary as the drain is being lined with materials in
excess of the requirements. It should be noted that the drain has been proposed and designed as an emergency




 SITE BASED STORMWATER MANAGEMENT PLAN - Revision D     / I Seaview Terrace, Sunshine Beach                          5