Bray Park Weir Tidal Protection Project

December 2024 project update
In November 2023, Council resolved to continue investigating options to raise the Bray Park Weir by either 800mm or 1300mm, to reduce the risk of saltwater contamination in the Tweed District water supply. In 2024, these 2 options were presented to Council at the December Council Meeting.

The 2 options were presented following thorough independent assessments and recent consultation with potentially impacted landowners.

At the 11 December 2024 Council Meeting, it was resolved that Council:

1. Further investigate the option of raising the Bray Park Weir by 800mm, including investigation of any downstream impacts and mitigation measures.
2. Continue targeted consultation with those who may be impacted by the raising of the weir.

Project overview

Council is progressing with vital work to secure our community’s tap water supply by investigating long-term solutions that would prevent saltwater from overtopping the Bray Park Weir.

From 1 January 2017 until 2 October 2024, there have been 90 overtopping tidal events, with 66 requiring blocks to be deployed for a total of 570 days to prevent saltwater from entering the weir pool.

This project is critical to protect the Tweed’s tap water supply from saltwater contamination and ensuring long-term sustainability in the face of rising sea levels.

Where we are now

Further investigating the option to raise the weir by 800mm: At the 11 December 2024 Council Meeting, Council resolved to further investigate raising the weir by 800mm—including investigating any downstream impacts and mitigation measures—and continue consultation with potentially affected landowners and stakeholders.

Raising the weir by 800mm would offer long-term protection for the Tweed’s water supply until around 2050, while also allowing for the weir to be raised further to 1300mm in the future if needed.

How we got here

• Previous investigations: Council formed a project reference group in 2017 to identify and assess options to reduce the risk of saltwater contamination of the Tweed water supply. The group identified a range of options including:
  • a hinged barrier across the entire weir
  • continued use of concrete blocks
  • narrowing the weir
  • moving the intake of the Bray Park Water Treatment Plant
  • raising the weir.

After the group recommended a hinged barrier, consultants engaged by Council conducted a detailed investigation, which found this option unworkable. The group ranked other options, including narrowing the weir and raising the weir. An investigation by consultants into narrowing the weir determined this option unviable because it would provide limited protection to the water supply. The continued use of concrete blocks doesn’t provide adequate protection against overtopping events and the manual installation and removal of the blocks is unsafe. Moving the intake of the treatment plant upstream would significantly reduce the catchment area of the Tweed district water supply, decreasing the amount of water available for most of the Tweed.

• Independent investigations into 2 weir raising options (2024): In September 2024, independent consultants GHD conducted detailed studies on options to raise the weir by 800mm and 1300mm. This considered issues such as flooding, impact on infrastructure and changes to the landscape.
  
  
• Targeted consultation for the 2 weir raising options (2024): In November 2024, we sought feedback of landowners who potentially could be impacted by raising the weir. 7 submissions were received. These submissions were included in the December 2024 Report to Council.

Learn more

We have compiled key information to help you better understand the 2 options and the potential impacts. Please take a look at these resources.

> Bray Park Weir Raising Assessment

The purpose of this report is to provide a summary of the investigations of the hydraulic impacts of raising the weir by 800 mm and by 1300 mm.

> Bray Park Weir Raising Assessment - Appendices (Flood Mapping and Fishway Layout Options)

Flood mapping, presenting the results of the flooding assessment for each scenario, is provided in Appendix A. A concept fishway layout has been developed for the 2 raising scenarios and included in Appendix B.

> Bray Park Weir Concept Design

This report aims to:

• document the data provided by Council and other sources that would be used to develop the concept design
• review relevance of the data in its ability to inform the design process
• undertake an assessment of what data was not provided and its impacts on the design process
• provide a summary of the basis of design for the weir and fishway to set the guiding criteria for the project moving forward.

> Bray Park Weir Concept Design Report

This report aims to document the:

• assessment of options to raise or narrow the weir
• outcomes of the preliminary desktop assessment to review 3 permanent weir raising options
• structural and geotechnical impacts of these works on the existing structure and its foundations.

> Bray Park Weir Review of Gate Options

This document provides a summary of information on hinged barrier options presented to Council. It summarises GHD’s opinions on the various technologies and provides scoring based on qualitative assessment of the options.

Ask us a question

Do you have any questions about the project or the options under consideration? We’re here to help. Use the form below to ask a question, and we will respond as soon as possible.

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Frequently asked questions (FAQs)

We’ve compiled a list of frequently asked questions to help address the most common queries about the project, its impacts and what the next steps are. You can access them on this webpage.

Q1: Why is Council looking at raising the weir?

The weir is under increasing risk of saltwater overtopping due to rising sea levels. This could jeopardise the supply of tap water for most of the Tweed. Raising the weir would safeguard this essential water source for years to come.

Q2: How often is the weir being overtopped by saltwater and blocks deployed?

From 1 January 2017 to 2 October 2024, there have been 90 overtopping tidal events, with 66 requiring blocks to be deployed for 570 days to prevent saltwater entering the weir pool. This has become a problematic risk to manage. Overtopping events have been occurring more frequently and on occasions twice a month. The frequency of events is well in excess of Water Research Laboratory predictions.

In the past year, the fishway has been blocked for 158 days to prevent saltwater from contaminating the Tweed District water supply. Any mitigation measure to prevent the saltwater contamination will need to consider fish passage.

Q3: What are the differences between raising the weir by 800 mm and by 1300 mm?

Raising the weir by 800 mm would protect our water supply from saltwater contamination until around 2050, while raising it by 1300 mm would extend protection until 2100. More details are available in the GHD Bray Park Weir Raising Assessment.

Q4: Would raising the weir increase flood risks upstream?

There would be increases in water levels during floods immediately upstream of the weir. However, further upstream the increase would be minimal. For example, at Byangum Bridge, the increase would be about 10 mm during large floods. More details can be found in the GHD Bray Park Weir Raising Assessment.

Q5: Can’t we continue to rely on weir blocks?

Since 2017, our workers have been managing overtopping events by manually installing concrete blocks to narrow or block the weir. The blocks are removed when the risk has passed. While the blocks reduce the risk of saltwater contamination, they don’t fully mitigate the risk and the manual installation and removal is a safety concern. The fish ladder in the weir must also be blocked in these events, impacting the movement of fish in the river.

Read more FAQs