Short Virtual Presentation & Digital Poster 10th Australian Stream Management Conference 2021

Exploring the relationship between channel bed control structures and stream power in low-gradient floodplain wetlands (#32)

Timothy J Ralph 1 , Zacchary T Larkin 1 2 , William Farebrother 1 3 , Joanne Ocock 4 , Tim Hosking 5 , Tsuyoshi Kobayashi 2 , Michael Hughes 2 , Paul Hesse 1 , Kirstie Fryirs 1
  1. Faculty of Science and Engineering, Macquarie University, North Ryde, NSW, Australia
  2. Science, Economics and Insights Division, Department of Climate Change, Energy, the Environment and Water, Lidcombe, NSW, Australia
  3. School of Environmental and Life Sciences, College of Engineering, Science and Environment, University of Newcastle, Newcastle, NSW, Australia
  4. Northern Inland Branch, NSW National Parks and Wildlife Service, Narrabri, NSW, Australia
  5. Biodiversity and Conservation Division, Environment, Energy and Science Group, Department of Planning, Industry and Environment, Dubbo, NSW, Australia
Floodplain wetlands are complex fluvial systems that provide critical ecosystem services. Some floodplain wetlands suffer from erosion that threatens to create and enlarge channels and potentially disconnect wetlands from vital overbank flows. Excessive channel erosion can have dramatic effects on flow routing, inundation patterns and aquatic ecosystem dynamics. Channel erosion is sometimes mitigated by the use of bed control structures to arrest bed lowering and associated channel enlargement. Stream power modelling techniques based on Digital Elevation Models (DEMs) have rarely been used in low-gradient rivers and wetlands. A modified stream power modelling method was used to identify hotspots of enhanced stream power, and therefore potential erosion risk, in the Ramsar-listed Macquarie Marshes, NSW. Peaks in stream power occur where pronounced steps exist in channel longitudinal profiles, most notably at rock bed control structures. In low-gradient floodplain wetlands, local over-steepening within the channel is associated with increased stream power and erosion potential. Stream power modelling provides an important screening tool to prioritise sites for detailed investigation and erosion assessment. Ultimately, such modelling can guide further monitoring and/or interventions to reduce the risk of erosion and ecological deteriorations.
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