Flood Investigation & Stormwater Quantity Management Plan

Flood Investigation & Stormwater Quantity Management Plan
Proposed Residential Development at Doonella - Stage C


          FLOOD INVESTIGATION & STORMWATER QUANTITY
                       MANAGEMENT PLAN
             PROPOSED RESIDENTIAL DEVELOPMENT AT
                      DOONELLA - STAGE C

1.0 INTRODUCTION
Brown Consulting (Qld) Pty Ltd has been commissioned to undertake a Flood Investigation & Stormwater Quantity
Management Plan to support the Development Application for Stage C of the proposed “Doonella” residential
subdivision at Doonella - Stage C.
This report outlines the stormwater management strategies that will be adopted for the development to ensure there
are no adverse flood impacts to adjacent properties as a results of the development. The scope of the investigation
undertaken and discussed in this report is as follows:
      •   Hydrological investigations and modelling to determine existing peak flows and post development peak flows
          at the downstream site extent;
      •   Modelling to determine likely changes to peak flows at the downstream site extent that results from the
          proposed residential subdivision;
      •   Development of a management strategy to mitigate increases in peak flows resulting from the proposed
          residential subdivision at the downstream site boundary, with modelling to confirm the effectiveness of the
          strategy; and
      •   Hydraulic modelling to determine post development flood levels to confirm proposed lot and road levels have
          appropriate freeboard or acceptable flood immunity along the environmental corridor through the site.

1.1       Past Studies
Various stormwater management plans and related documents have previously been approved by Council prior to the
‘Change to an Existing Approval Decision Notice’ issued by Council on 9 May 2008.
The stormwater management plans and related documents prepared by WBM Oceanics Australia did not investigate
flooding in the environmental corridor. The design intent and function proposed by WBM Oceanics Australia for the
management of stormwater at the Doonella subdivision has been considered when reviewing road and lot levels for
the proposed development however, this flood investigation report has been written as a stand alone document and
does not refer to the WBM Oceanics Australia reports. The influence of flows in the environmental corridor as
determined by this report will not impact on stormwater quantity and quality outlets and infrastructure, and the WBM
Oceanics Australia approved Stormwater Management Plan does not need to be altered to account for the outcomes
of this flood investigation.
The detention basin design and stormwater management strategy for the adjacent residential development located at
the downstream end of the environmental corridor was prepared by JF&P Consulting Engineering Pty Ltd. The JF&P
Site Based Stormwater Management Plan, Beckmans Green Noosaville (Report No. M2099_SBSMP_Rev_D dated
June 2008) details the management strategy for that development and is referred to within this Flood Investigation.




B09182.W-02A                                                                                                    Page 1