2016-07-18 General Committee Meeting - Item 3 - Attachment 1 - Flood Management Plan

5.4 Coastal and Storm Tide Studies                                     5.4.1.2     NDRP Storm Tide Hazard Interpolation
                                                                                   Study (GHD)




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5.4.1.1    Sunshine Coast Storm Tide Study (Aurecon




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           2013)                                                       The NDRP Storm Tide Hazard Interpolation Study15 was




                  A
                                                                       undertaken by GHD on behalf of the Department of




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The Sunshine Coast Storm Tide Study was commissioned                   Science, Information Technology, Innovation and the Arts
by the Sunshine Coast Council prior to de-amalgamation                 (DSITIA). DSITIA were seeking information on the risk of
and completed by Aurecon in December 2013.                             storm tide hazards across the State that would identify the
As a part of the Storm Tide Study a new Noosa River                    relative likelihood of specific communities being subjected
TUFLOW (Classic) model was prepared using a detailed                   to dangerous inundation events.
nested 2D grid and drawing on available survey and                     The principal requirement of this study was to identify,
bathymetric data, along with the latest available LiDAR                based on a consistent methodology using data from
survey. Model calibration was undertaken to demonstrate                existing studies, the Average Recurrence Interval (ARI, or
tidal and storm tide performance at selected locations.                Return Period event) for a range of ocean water levels for
                                                                       each coastal LGA area. The minimum ARI levels required
The Noosa River TUFLOW Storm Tide model covers a large
                                                                       were the 20, 50, 100, 500 and 1000 y ARI event, plus the
computational area which includes the inter-tidal lakes in
                                                                       estimated Probable Maximum Level.
the upper estuary. A relatively coarse 40 m computation
grid was adopted to represent bathymetric and hydraulic                This was a state wide study with reference to Noosa and the
conditions over much of the model area. However, for                   Sunshine Coast.
the Noosa River entrance and the estuarine areas around
Noosa Heads, Noosaville and Tewantin higher resolution                 5.5 Key initiatives – Flood studies
was adopted to ensure model and mapping detail was
adequately represented. Accordingly, the model has been                The implementation plan will include initiatives that aim
prepared as a nested 2D2D model so that these areas could              to –
be modelled as higher resolution, but ensuring the dynamic              •   Prepare a flood study of Six Mile Creek using latest
interactions between the entrance areas and the upper lakes                 flood modelling techniques and standards that are
were maintained. The urbanised areas around the inlet were                  consistent with other flood models for the region.
modelled using a fine grid of 5 m. The nested high resolution
                                                                        •   Upgrade of the Noosa River Model to a contemporary
grid is 6.7 km by 5 km and covers the area from the estuary
                                                                            2D modelling platform and cover the major
inlet upstream to just north of Tewantin and south toward
                                                                            watercourses and floodplains to and beyond Kin Kin.
the entrance to Lake Weyba.
                                                                        •   Explore foreshore erosion within the lower reaches of
The river channels between the lakes, particularly                          the Noosa River using the Noosa River Model.
upstream of Tewantin and between Lake Cootharaba and
Lake Cooroibah, are relatively narrow and were poorly                   •   Include flood mitigation modelling for Daintree
represented at 40 m resolution. To address this, nested                     Estate, Cooroy Creek and Cooroora Creek for all
1D channels were introduced to represent the hydraulic                      design flood events in Council’s Flood Information
conveyance characteristics of these channels.                               Repository.
                                                                        •   Review the custodianship and management of
                                                                            Council’s flood study data (including spatial flood
                                                                            data files) with the view of establishing a clear point of
                                                                            contact with regards to flooding information.

 15
   NDRP Storm Tide Hazard Interpolation Study Report by GHD
 for Department of Science, Information Technology, Innovation and the Arts, May 2013




                                                                                        Noosa Council | Flood Management Plan | Page 21