MCU14/0106 Appendix E - Engineering Report

Noosa Civic
Stormwater Management Plan




2                 Stormwater Quantity Management
2.1               Regional Flood Mapping
Appendix A contains copies of Noosa Shire Council’s River Flood Information Map and Stormtide
Information Map. This mapping indicates that the site is effectively flood free from both River and Stormtide
flooding.
There is a small inundation extent on the site mapped for River flood for extreme events, but this does not
affect any land beyond the area identified as OS7. Therefore management of the stormwater and flooding
for this site will be based on local catchment management only.

2.2               Local Catchment Modelling
Unattenuated development would produce an increase in stormwater discharge from the site. Hydrologic
modelling was therefore undertaken to determine the detention volume required to mitigate this increase.
The hydrologic analysis was undertaken using the WBNM model in accordance with the requirements of the
Noosa Shire Council Planning Scheme (NSC, 2013), the Queensland Urban Drainage Manual (DEWS,
2013) and Australian Rainfall and Runoff (IEAust, 1998).
Two scenarios were considered for the assessment:
      Existing Scenario
       In the existing scenario the site drains to the west and south-west, primarily through the existing minor
       drainage corridor contained within OS7. Flows from the existing developed area of Noosa Civic to the
       west also contribute to the overall runoff in OS7. Flow is discharged from the site at three different
       points along the southern boundary. The existing site and catchments are shown on Figure 2.
      Developed Scenario
       For this scenario, the existing model was modified to include the proposed development based on the
       layout given in the reference drawings. The catchment boundaries for this scenario are shown on
       Figure 3.
Table 2-1 and Table 2-2 list the parameters adopted for the existing and developed scenarios respectively.
Table 2-1         Existing Catchment Properties

        CATCHMENT ID              Catchment area (ha)        Percentage Impervious
                                                                      (%)
                   A                     9.09                        15.28
                   B                     3.61                        5.61
                  C                      2.57                        26.30
                  D                      4.47                        85.00
                   E                     1.53                        5.00
                Total                    21.27                       28.89




QIC Noosa Civic Pty Ltd                              Version 1                                     November 2014
Appendix D - SMP.docx                                                                                    Page 2