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

Delineating multiple flow paths in anastomosing river systems with wetlands using DEMs (#8)

Timothy Ralph 1 , William Farebrother 1 2 , Zacchary T Larkin 1 3 , Joanne Ocock 4 , Carl Helander 1 , Neda Yousefi 1 , Tsuyoshi Kobayashi 3 , Paul Hesse 1 , Kirstie Fryris 1
  1. Faculty of Science and Engineering, Macquarie University, North Ryde, NSW, Australia
  2. School of Environmental and Life Sciences, College of Engineering, Science and Environment, University of Newcastle, Newcastle, NSW, Australia
  3. Science, Economics and Insights Division, Department of Climate Change, Energy, the Environment and Water, Lidcombe, NSW, Australia
  4. Northern Inland Branch, NSW National Parks and Wildlife Service, Narrabri, NSW, Australia

Anastomosing rivers with wetlands are difficult systems to measure and model using conventional geographic, hydrodynamic and morphodynamic tools. Successful environmental assessment, monitoring and modelling of these systems relies on realistic and accurate delineation of flow paths and channels. High-resolution Digital Elevation Models (DEMs) allow for improved flow path and channel delineation in low-gradient anastomosing rivers with wetlands. Several flow accumulation tools commonly used to derive drainage networks from DEMs in GIS software packages were reviewed, and the GRASS flow accumulation model was applied to a 1 m DEM of the Gwydir Wetlands, NSW. Flow convergence settings in GRASS yielded few variations, and all had limitations where channels became very small and entered wetlands. Zones of flow dispersal and channel breakdown were not easily identified. Manual adjustment of polylines derived from the model outputs were required to achieve the most accurate representation of major and minor flow paths. Identification and mapping of channel networks in anastomosing rivers with wetlands provides an improved understanding of the channel hierarchy and flow routing patterns. Ultimately, advances in channel delineation techniques can guide further research including hydrodynamic, morphodynamic and landscape evolution modelling to support environmental management. 

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