The Macquarie Marshes are an extensive wetland system located in central New South Wales within the lower Macquarie Catchment, representing one of the largest semi-permanent wetlands in southeastern Australia. The Marshes are one of most biologically diverse wetland systems in the Murray Darling Basin, and support some of the largest waterbird breeding events in Australia. A number of studies have demonstrated the critical role of inundation in maintaining the ecological values of the Marshes. The inundation extent, duration and depth of the core wetlands in the Marshes are variable over long and short time-scales, related to geomorphology and flow variability in the Macquarie River.
Processes of sedimentation and erosion underlie channel changes in the Marshes and have created a range of landforms with distinct characteristics and spatial distribution. As channels change and move on the floodplain, flooding and sedimentation patterns change and the wetlands respond by relocating, expanding and contracting. The streams and wetlands of the southern part of the Macquarie Marshes have been associated with notable hydrological and geomorphic changes over recent history including channel erosion, changing flow paths and reductions in wetland inundation. Some wetlands have been partly or wholly abandoned by the modern streams (e.g. Macquarie Terminus Marsh and Willie Marsh), while ecologically important wetlands have also developed and changed over time (e.g. Willancorah Swamp). In addition to natural fluvial landforms, there are many anthropogenic features (e.g. roads, levee banks, regulators and channels) that modify the natural landscape and influence flow in the system.
While channel change over time is a significant factor for wetland conservation, the impacts of channel change and potential intervention scenarios have never been assessed at the wetland system or sub-system scale in the South Marshes. In this study, we built a 1D/2D coupled hydrodynamic model (MIKE FLOOD) at fine spatial resolution (30 m) for the South Marshes. The MIKE FLOOD gives us the ability to evaluate the impacts of channel change on flow distribution both within channels and on the floodplain. We constructed and simulated three scenarios representing the baseline (i.e. no change to the current channel depth as in 2008), worsening (i.e. erosion keeps on going resulting deepened and built-up channels), and improved (through channel stabilizing etc.). The flow distribution and inundation extent under the three scenarios were compared for low, medium and high flows. The results showed that there were substantial differences in flooding patterns in terms of river flow distribution, flow breaking (into floodplain) locations, and inundation extents even for low flow conditions. However, the biggest changes were for medium flow. The study demonstrated that hydrodynamic models could be a useful tool in floodplain restoration through comparing the outcomes of alternative remediating works and predicting the outcomes of proposed works on wetland system hydrology and inundation patterns.
|Title of host publication||20th International Congress on Modelling and Simulation (MODSIM2013)|
|Editors||Julia Piantadosi, Robert Anderssen, John Boland|
|Place of Publication||Australia|
|Publisher||Modelling & Simulation Society Australia & New Zealand|
|Number of pages||7|
|Publication status||Published - 2013|
|Event||20th International Congress on Modelling and Simulation (MODSIM) - Adelaide, Australia|
Duration: 1 Dec 2013 → 6 Dec 2013
|Name||Proceedings - 20th International Congress on Modelling and Simulation, MODSIM 2013|
|Conference||20th International Congress on Modelling and Simulation (MODSIM)|
|Period||1/12/13 → 6/12/13|
- MIKE FLOOD
- Channel erosion
- South Macquarie Marshes
- FLOODPLAIN EVOLUTION
- ARID AUSTRALIA
Wetlands in Drylands: conservation through environmental research, citizen science and global engagement
Tim Ralph (Participant)
Impact: Science impacts, Environment impacts, Policy impacts, Society impacts