Pre-Request Response Application 132001.210310.1

Flood Investigation & Storm water Quantity Management Plan                                             BROWN
                                                                                                              s,_,.,lliter
Proposed Residential Development at Doonella Stage C
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5.0      CONCLUSIONS
This Flood Investigation and Stormwater Quantity Management Plan has been prepared to support the Development

Application for Stage C of the proposed ’Doonella’ residential subdivision at Beckmans Road Noosaville.
The report has addressed the management of peak flow increases generated by the site development and flooding
within the proposed environmental corridor.

The outcomes of these investigations are as follows:

    .
         Hydrological modelling has determined that without mitigation, peak flows at the downstream site boundary
         will increase as a result of the proposed development;

         A management strategy is proposed to mitigate the increase in peak flows.            Designs for two detention
         storages, being the embankment across the environmental corridor to form the Dodonaea Road crossing and
         the Bio-Retention Basin at the lower end of Twigrush Court, have been modelled. The results indicate the two

         detention storages will reduce peak flows to existing values at the site boundary.

    .
         Using peak flows for the 100 year ARI event (determined as part of the hydrological analysis) flood levels and
         extents within the environmental corridor within and downstream of the site have been determined. The

         modelling results indicate that more than sufficient freeboard will be provided to proposed allotments.
         Furthermore the limited depth and velocity of flows overtopping the Dodonaea Close crossing will ensure it is

         trafficable during the 100 year ARI event.


6.0      RECOMMENDATIONS
It is recommended that this Flood Investigation and Stormwater Quantity Management Plan be approved and the

strategies within be incorporated into detailed design. Detailed design and construction drawings are to be undertaken
and submitted with the Operational Works application.        Detailed design may result in changes to the proposed

management strategies but the design objectives will be maintained.




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