Seaham Weir Pool Erosion Management
Hunter Water is remediating eroding riverbanks on the Williams River between Seaham and Clarence Town. This will help prevent further erosion and improve water quality.
Progress update
Remediation work will take place in stages, with the first stage of work now underway for those landowners who have committed to the project with a signed agreement.
The first package of stabilisation work is progressing well. Log structures have been installed in the river to help prevent river bank erosion, with weed management, and installation of stock management fencing underway. Re-vegetation of river banks is also underway, using a range of native plants.
Most work is being carried out from 7am until 6pm Monday to Friday, and Saturday from 8am to 1pm.
Project background
The section of the Williams River between the Seaham Weir and Clarence Town, known as the Seaham Weir Pool, is highly valued by the local community. Around half the water in Grahamstown Dam is pumped from Seaham Weir Pool on an ongoing basis, providing drinking water for over half a million people in the Lower Hunter.
The Seaham Weir Pool requires active intervention to stop ongoing bank erosion and stabilise banks in the long term. This will help improve water quality now and into the future.
Several government agencies collaborated to develop an Erosion Management Plan (EMP) for Seaham Weir Pool. The Plan is a product of expert studies, government agency expertise, and feedback from the local community, landholders, boaters and other waterway users. The Plan includes a program of remediation work to repair and stabilise eroding river banks.
Hunter Water has been tasked with carrying out the remediation program and has engaged NSW Soil Conservation Service (SoilCon) to complete river bank stabilisation works.
The Seaham Weir Pool remediation program is funded by Hunter Water and the NSW Government.
How will river banks be stabilised?
Along severely eroded stretches, work will involve a combination of engineered structures (log and/or rock), bank revegetation, weed removal and stock management fencing. Indicative images are below.
Stretches with less severe erosion will require revegetation on the riverbanks, weed removal and stock management fencing.
Where river banks are currently showing little erosion with good vegetation, no works are proposed at this stage.
Indicative images:
Did you know ...
Many of the logs used for the Seaham Erosion Management program have been sourced from the nearby M1 Pacific Motorway extension to Raymond Terrace project, with thanks to Transport for NSW and their construction partners, John Holland Gamuda and Seymour Whyte.
Not only does this reuse help minimise the amount of timber going to mulch, firewood and waste, but using native logs in-river will help create habitat for aquatic species, sunbaking spots for reptiles, trap debris from floods, and provide shade to regulate water temperature.
Frequently asked questions
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Why are Hunter Water and the NSW Government investing in erosion management?
The results of long-term water quality monitoring in the Seaham Weir Pool show a gradual and continuing deterioration in water quality, which can be attributed to ongoing bank erosion, among other causes.
A 2015 study conducted by University of NSW’s Water Research Laboratory (WRL) stated the leading causes of bank erosion in the weir pool are a combination of historical and current land practices, flood events, and wake-generating boating activities.
The Australian Drinking Water Guidelines (ADWG) states that the most effective and efficient way of assuring drinking water quality and the protection of public health is through the adoption of a preventive management approach that encompasses all steps in the water supply chain, from catchment to consumers. Effective management of our drinking water supplies requires governments, water utilities, land management agencies, landholders and other custodians to work together to put in place a range of measures across multiple barriers.
Catchment management and the protection of source water is the first barrier for the protection of water quality. Effectively managing erosion within Seaham Weir Pool will improve the protection of this important drinking water source in line with relevant public health requirements, including the ADWG, which advocates that source waters should be protected to the maximum degree practicable. Compliance with the ADWG is a requirement of Hunter Water’s Operating Licence.
Remediation work will repair and stabilise eroding banks to improve the long-term resilience of the weir pool for the benefit and enjoyment of all users.
Read more about erosion and water quality in our fact sheet.
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Is our drinking water safe if water quality in the weir pool is a concern?
We adopt a precautionary approach to harvesting water from the Williams River for treatment and supply to customers and the community. This includes not using water from a particular source if water quality does not meet specified criteria.
The measures we have in place to ensure the safety of drinking is never compromised include:
- robust multi-barrier water treatment processes
- routine water quality monitoring
- the ability to switch between different water sources
- continuous system monitoring, and
- regular liaison with NSW Health on water quality.
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Are there any plans to introduce further boating restrictions for the Seaham Weir Pool?
Transport for NSW’s existing boating management plan for the weir pool will be retained. This plan permits certain high wake-generating boating activities within designated zones of the weir pool and aims to help prevent riverbank erosion.
By retaining this plan, two important factors are addressed:
- the social and economic benefits boating brings to the local area, particularly Clarence Town
- the potential transfer of the erosion problem to other local waterways if a ban on wake-generating boating activities in the Seaham Weir Pool was introduced.
Some additional temporary boating restrictions are expected to be required during bank remediation works, causing short-term inconvenience to some river users. Any temporary restrictions will be communicated to local residents and weir pool users in advance where possible.
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What consultation has occurred already?
In 2016 community feedback was invited on the University of NSW’s Water Research Laboratory’s 2015 report Riverbank Vulnerability Assessment using a Decision Support System: Seaham Weir Pool and Lower Williams River (the WRL report).
A total of 119 submissions were received from a range of stakeholders, including recreational boaters, landowners along the affected river stretches, local residents and owners of businesses dependent on use of the river for recreation.
The feedback received informed the revised draft Erosion Management Plan which was on public exhibition from Tuesday 25 October to Tuesday 22 November 2022. During this time, a total of 45 meetings and discussions were held with potentially directly affected landowners in the project area and 23 formal submissions were received.
The feedback received during the public exhibition period has been collated in a Community and Stakeholder Engagement Outcomes Report.
After consideration of the feedback received during the public exhibition period, the Seaham Weir Pool Erosion Management Plan has been finalised.