Amended Stormwater Managment Plan

SC5594 – Walter Hay Dr, Noosaville                                                                14




4.3.6    On-Site Detention
It is calculated from the development site plan that the proposed development will increase impervious
areas on the site from 0% to 55%. The proposed increase in impervious areas has the potential to increase
peak flow rates to the existing drainage system. To mitigate potential increases in flow rates it is planned to
detain stormwater flows on-site and discharge at a mitigated rate to the existing swale.


Mitigation of flow is provided by the following volumes:
         Approximately 356m3 of total detention volume within the Bio-retention basin from FSL to the
         maximum water level. Flows from this storage volume will be throttled by a reduced cross-sectional
         area connection at the Bio-retention basin outlet (225mm), and an overflow weir;
         A combined 48m3 (25m3 + 23m3) within small areas of ponding in the carpark. The storage areas in
         the carpark will not exceed 290mm in depth for the major event. The maximum depth for still water
         at a sag location in accordance with QUDM is 300mm for a major event.



Refer to Figure 4.2, 4.3, and 4.4 for depth volume relationships modelled.




                      Figure 4.2 – Bio-Retention Basin Detention Storage Parameters