Funded by:
The Great Barrier Reef Foundation and the Australian Government’s Reef Trust
Partners:
The Mary River Recovery Consortium, made up of Burnett Mary Regional Group, Alluvium Consulting and Mary River Catchment Coordinating Committee
Background:
Australia’s irreplaceable Great Barrier Reef ecosystem is under threat due, in part, to poorer water quality runoff. The Mary River is one of the top five contributors of fine sediment into the Great Barrier Reef, with catchment modelling showing around 70% of the fine sediment from the Mary River that enters the Great Sandy Strait comes from streambank erosion.
The Great Barrier Reef Foundation, together with the Australian Government’s Reef Trust, has invested $9.4M in solving this issue, to build on the high calibre of work already being undertaken by Queensland’s farmers and agricultural community to help reach the targets set out by the Reef 2050 Water Quality Improvement Plan.
The main aim of The Mary River Recovery Program is to stabilise and revegetate badly eroding sections of the Mary River by working directly with cooperative landholders over a four-year period.
Burnett Mary Regional Group leads the Mary River Recovery Consortium (MRRC), a formal delivery group partnership between Burnett Mary Regional Group, Mary River Catchment Co-ordinating Committee, and Alluvium Consulting, which are all committed to this project.
Issue:
Catchment modelling shows that approximately 70% of the fine sediment that enters the Great Sandy Strait from the Mary River is from streambank erosion. Each year, 26 000 tonnes of sediment enter the Great Barrier Reef lagoon from just eight Mary River erosion sites. Streambank retreat and increased amounts of sediment not only negatively impact the Great Barrier Reef, but also impact the endangered Mary River cod and white-throated snapping turtle through the loss of nesting and feeding grounds. The collapse of streambanks block the river systems, preventing fish movement and smothering food sources.
Solution:
To address the source of fine sediment pollution in the Mary River catchment, large-scale restoration of eroding riverine areas is needed. This restoration includes streambank stabilisation (earthworks, pile field installation, rock chutes) and revegetation to restabilise banks and slow the flow of water over the bank. Community engagement through education helps improve land and streambank management practices in the Mary River catchment.
Project Scope:
Over four years, ending June 2024, weak points along the Mary River banks will be stabilised. Sites were determined according to where sediment saving was most cost-effective for the project and landholder cooperation. In-kind contributions are being negotiated with landholders, including riverbank fencing and environmental weed control. This project will further strengthen the culture of catchment management within the community, already established through BMRG’s existing on-ground projects.
Work done to date:
Seven sites have now been fully rehabilitated as part of the Mary River Recovery Program. This rehabilitation has included detailed engineering design, major earthworks and bank reprofiling, pile fields, revegetation and maintenance, monitoring and evaluation. More than 35 stakeholders and landowners toured to see the progress update and identify future opportunities.
An aerial survey was also completed to assess how rehabilitated sites withstood extreme weather (such as Cyclone Seth and subsequent flooding) and document damage to unrehabilitated sites. Fortunately, the rehabilitated sites had minimal damage, demonstrating that the earthworks, pile fields and revegetation have been successful in stabilising the streambanks. Meanwhile, unrehabilitated sites showed significant bank retreat, vegetation loss and self-battering.
Design plans for the remaining sites are planned. Due to extreme weather and further damage these sites may require further review and design changes prior to site work.
Future work:
Five new sites have been selected to continue streambank stabilisation and rehabilitation.
Recent flood damage (January – March 2022) will be reviewed and repair work undertaken.
Continuous monitoring of sites and water quality will continue until the project’s completion in June 2024.
