National Wetlands Update September 2012
Issue No. 21, September 2012
Southern Macquarie Marshes stream enhancement project
Tim Hosking, New South Wales Office of Environment and Heritage
The Breakaway channel, Macquarie Marshes Nature
Reserve (south). September 2010. (Tim Hosking
and New South Wales Office of Environment and
A new project is underway to maximise the environmental benefits gained from floods and environmental flows in the southern Macquarie Marshes and to help protect downstream wetlands.
The geomorphic characteristics (e.g. size, shape and location) of channels and wetlands in the Macquarie Marshes, in north central New South Wales, have changed considerably in the past 50 years. While gradual channel change and the occasional movement of channels on the floodplain are natural processes, human activities have affected key aspects of the system, such as:
- additional erosion and channel scouring due to change in river flows reaching the marshes (related to river regulation and floodplain development)
- increased sediment loads entering the marshes from catchment disturbance
- de-stabilisation of stream banks due to a combination of factors such as hydrology, drought, invasive species and land use
- historical stream intervention works leading to further changes over time, such as a block banks and weirs that are unsuitable for current conditions.
The changes to channel profiles have contributed to ecological degradation in some areas of the Macquarie Marshes, particularly where floodplain wetlands have become disconnected from their feeder streams.
Existing in-stream erosion and sediment control
works in 'The Breakaway' channel, Macquarie
Marshes Nature Reserve (south). (Tim Hosking and
New South Wales Office of Environment and Heritage)
The southern area of the Macquarie Marshes in particular has undergone, and continues to undergo, significant channel changes and associated degradation of floodplain wetlands on both public and private lands. This section of the marshes is the first major filter for sediment entering the system from upstream and acts as a buffer zone between the river and other high conservation value wetlands further downstream.
The Southern Macquarie Marshes Stream Enhancement Project will identify potential erosion control and stream restoration works and will examine the hydrological effects of such measures at the wetland system level. The project will ultimately deliver a recommended plan of works and measures that will aim to restore floodplain connectivity to maximise the ecological benefits from floods and environmental flows.
These works will also directly protect wetlands downstream by reducing the transport of silt that chokes channels causing redirection of water and increased stream instability.
The project began in April 2012 and will be completed by early 2013. The project is managed by New South Wales Office of Environment and Heritage in association with Barma Water Resources. A steering committee comprising government and land manager representatives has been established to support the project.
The project is funded under the Australian Government's Environmental Works and Measures Feasibility Program.
For further information on the project contact: Tim Hosking NSW Office of Environment and Heritage, Dubbo email@example.com or Daren Barma Director, Barma Water Resources firstname.lastname@example.org