MCU14/0106 & OPW15/0001 Appendix E - Stormwater Management Plan

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 flood analysis was undertaken using the XP-SWMM 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). This modelling tool considered an integrated
hydrologic and hydraulic model, whereby the catchment runoff was directly input into storages and
stormwater link elements.
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
      proposed uses shown on the layout included in the reference drawings. The catchment boundaries for
      this scenario are shown on Figure 3.

2.2.1            Hydrologic Model Details
Table 2-1 and Table 2-2 list the parameters adopted for the existing and developed scenarios respectively.




QIC Noosa Civic Pty Ltd                          Version Final                                      11 May 2015
J13041R2_Final SWMP.docx                     Commercial in Confidence                                    Page 2