Macquarie River rafts
Information about debris rafts recently formed along the Macquarie River.
Following recent flood events in NSW, debris rafts have formed along the Macquarie River, north of Warren.
Debris rafts are comprised of organic and anthropogenic (human derived) materials.
The Environmental Services Functional Area (the EPA is the lead agency) is working with other agencies and the community as part of coordinated environmental recovery. The EPA has no regulatory role.
The EPA is consulting with other government agencies to address the issue and engaged a consultant in hydrogeomorphology, EMM Consulting, for an independent expert opinion.
EMM Consulting provided a report (PDF 12MB) which found the debris rafts only have the potential to restrict flow and become hazardous in the Macquarie River channel during significant flood conditions when the river is flowing at or near bank full.
The report also found that the debris rafts have been forming for several years and have not directly resulted in significant flood damage despite the noteworthy river heights and flood volumes experienced in the 2022 events.
The NSW Government held a drop-in session in February in Warren to discuss management options for the rafts. The session provided feedback and insights into community concerns and the potential risks associated with rafts and proposed approaches to manage the rafts.
Environmental Services Functional Coordinator has considered the findings of this report and the views of the community and the State Recovery Committee has approved the partial removal of Macquarie River rafts, known as rafts four and seven.
The EPA is coordinating this work and will engage a contractor to complete the works.
The extent of the rafts to be removed from the Macquarie River will be determined by a risk-based assessment. The focus of debris removal will be on hazardous, manmade and exotic woody debris.
All works will be planned and coordinated in a manner that is safe to the environment.
Monitoring is being undertaken before and after the partial removal of the rafts to understand the impacts of the removal of debris. Monitoring includes water levels and flow and water quality. A broader monitoring program covering erosion potential, water levels and flow and water quality along the length of the Macquarie River where other rafts are present started in June 2023 and is being led by the Department of Planning and Environment.
Community feedback and questions
A risk-based approach to raft management is being undertaken. In addition to community feedback, considerations include: whether the rafts are anchored or floating; the nature of the debris in the rafts: manmade, hazardous, exotic woody debris, native woody debris; and impacts on water flow, fish passage and bank erosion.
The State Recovery Committee has approved removal works at rafts four and seven. The focus of debris removal will be on hazardous, manmade and exotic woody debris.
A monitoring program covering erosion potential, water levels and flow and water quality along the length of the Macquarie River where rafts 1, 2, 3, 5 and 6 are present will also be implemented.
Based on their understanding of fish behaviour in the Murray Darling Basin, DPI Fisheries advises that it is unlikely that the rafts, including the anchored rafts, are acting as a barrier to fish passage or impacting fish navigation due to decreased light conditions.
DPI Fisheries will be undertaking native fish movement research along the Macquarie River over the coming months in association with the Commonwealth Environmental Water Office related to water for the environment, which may provide an opportunity to assess fish movement related to the rafts.
DPI Fisheries advises that native woody debris plays an important role in rivers for fish habitat and productivity and should be retained where possible.
Based on in-field observations in December 2022 and February 2023, EMM Consulting advise that this may occur if water levels upstream of raft four increased by approximately 1.5 m or, if Bulla Bulla Creek has been enlarged and deepened, at a lower water height.
The Macquarie River raft monitoring program will include cross sections of the river and Bulla Bulla Creek and water level measurements which will inform understanding of this issue.
In-field observations, use of aerial photography and drones can provide a broad classification of the composition of the rafts. The debris, particularly whether the woody debris is native or exotic, would be better characterised during removal.
We’ll be doing this during partial removal of rafts four and seven. This will also allow for stockpiling of large native woody snags for possible reintroduction into the river system.
WaterNSW has advised that it is possible to restrict water flow to conduct works, such as debris removal, in the river. However, there are a range of issues that need to be addressed and it would require detailed planning and consultation with various stakeholders. This includes consideration of minimum environmental flows or targets at points along the river and obligations under existing work approvals and water sharing plans.
In the first instance, further details regarding the proposed debris removal works are needed.