An Investigation into Potential Operational Enhancements for the Tweed River Entrance Sand Bypassing Project
The Tweed River Entrance Sand Bypassing Project (TRESBP) is a joint scheme of the NSW and Queensland Governments. The primary objectives of the project are to establish and maintain a navigable entrance to the Tweed River and to restore and maintain the coastal sand supply along the southern Gold Coast beaches.
The TRESBP achieves this by capturing the majority of the northward moving coastal sands at a sand bypassing jetty before it reaches the river entrance. The sand is then pumped through a pipeline and under the Tweed River generally to the primary outlet beneath Point Danger, to the north of Duranbah Beach. Because of the location of the primary outlet, Duranbah Beach requires periodic nourishment. Pumping to Duranbah Beach occurs on average twice per year prior to stormy seasons. On a few occasions, sand has been pumped to outlets at Snapper Rocks West and Kirra Point. Sand that is discharged from the outlets is moved onto and along the southern Gold Coast beaches by the action of ocean tides, currents and waves. Access diagram showing Basis of outlet usage.
Not all of the sand moving northwards is captured by the jetty pumping facility, particularly during storm events. Sand that is driven by storms into the entrance of the Tweed River forms an entrance bar over time, which impedes safe navigation by vessels. A floating dredge is used occasionally, depending on the amount of shoaling within the river entrance, to help maintain the entrance navigation conditions as part of the sand bypassing operations. The sand removed from the entrance channel is deposited by the dredge in the project's designated nearshore sand placement areas (PDF 183kb) north of the river entrance, but generally offshore of Point Danger.
In the initial years of system operation, large volumes of sand were extracted and delivered by the project to clear the Tweed River entrance bar and restore the severely eroded southern Gold Coast beaches. Prolonged calm weather over the early to mid 2000's resulted in slower than predicted sand movement along the southern Gold Coast beaches. These factors contributed to the formation of wide beaches in Coolangatta Bay and at Kirra and accumulation of sand around Kirra Reef.
While recent studies have shown that the excess sand volumes are naturally dispersing from Coolangatta Bay, (Coolangatta Bay Sand Volumes) community concerns led to a campaign for changes to the operation of the system. In response the TRESBP implemented several strategies for reducing sand supply into the bay to aid the dispersal of the sand build up. The NSW and Queensland Governments also agreed to investigate the feasibility of four potential options for enhancing the longer term capability of the system to better achieve project objectives in the highly variable natural environment. The options investigated were:
- A new sand delivery outlet at North Kirra with an extension of the existing sand delivery pipeline by slightly over one kilometre,
- Additional Dredge Placement Areas potentially located along Bilinga and Tugun beaches about three kilometres to the north of the project placement areas, and also in deeper waters further offshore of the existing Point Danger to Coolangatta nearshore sand placement areas,
- Delivery of sand dredged from the Tweed River entrance to Kingscliff for beach nourishment of the eroded south Kingscliff Beach, and
- Sand Back-passing by either dredge placement and/or pumping of sand southwards along Letitia Spit Beach.
The following consultants undertook the feasibility studies:
- GHD undertook the assessment of the North Kirra outlet, alternative dredge placement locations and sand delivery to Kingscliff.
- BMT-WBM investigated the feasibility of the sand back-passing option.
- GHD also prepared the Summary Report to provide an overview of the assessment of all four options.
Use the link below to view the Options Feasibility Summary Report (PDF 946kb).
A community information evening regarding the feasibility options was held at the Tweed Heads Community and Civic Centre on 2 November 201 and feedback from the community on the feasibility options was sought up to 30 November 2011. The comments received by the community have now been reviewed and a summary report compiled and the report can be viewed here.
Other reference reports can be accessed through the links below,
'Feasibility Study of Sand Placement Options for System Augmentation', by GHD (PDF 8.0mb)
'Sand Back-Passing Feasibility Assessment', by BMT-WBM (PDF 1.2mb)