5179Flood Report_REV_3

                                                                                                         Callaghan & Toth




1.0       INTRODUCTION
This Flood Study has been prepared as part of a Reconfiguration of a Lot (RAL) application to Noosa Council.

The lot contributing to the overall development and subject to this report is shown in the Site Location Plan, Figure
1.1, below, and is described as Lot 3 on RP113733, located at 2 Pearsons Road, Cooroy. The existing topography of
the site and the relevant catchment areas are shown in Figure 1.2 on the following page of this report, together with
the proposed development layout on Figure 1.3.

The north-east corner of the site is traversed by the floodway of a tributary of Six Mile Creek, and a minor waterway
flows in a north-easterly direction across the middle of the lot.

The increased stormwater runoff from the proposed residential areas will be mitigated by an off-line detention basin
linked to a flow profile control in the minor waterway, as shown in Figure 1.3. The development proposal is
particularly cognisant of the need to not adversely affect the storage-routing capacity of the adjoining floodway and to
not increase local stormwater peak discharge rates to that floodway.

The assessment process was therefore structured as follows:

•         Abstraction of the Year2100 1%AEP flood levels from a 2014 flood model of the adjoining floodway
compiled by Brisbane Stormwater Management Pty Ltd, so as to define the floodway boundaries, and then ensuring
that the new lots are flood-immune and the stormwater detention facilities to not intrude into that floodway - as
described in Section 2.0 of this report.

•         Determination of the required detention volume so as to match the post-development peak discharges to
the pre-development peak discharges, from 1 year ARI to 100 year ARI, and proposing a detention arrangement that
will achieve that volume – as described in Section 3.0 of this report




                                                                                Site location




Figure 1.1:         Site Location


                                                                                                                  4
2035 2 Pearsons Road – Flood Study – Revision 3                                                  April 2021