Changes in Inundation Patterns for Anastomosed River Landscape Units at Decadal Scales — ASN Events

Changes in Inundation Patterns for Anastomosed River Landscape Units at Decadal Scales (#261)

Danuta Kucharska 1 , Michael J Stewardson 1 , Dongryeol Ryu 1 , Justin Costelloe 1 , Neil Sims 2 , Gini Lee 3
  1. Department of Infrastructure Engineering, University of Melbourne, Melbourne
  2. CSIRO, Clayton
  3. Faculty of Architecture, Building and Planning, University of Melbourne, Melbourne

Flow patterns within heavily anastomosed river reaches are difficult to analyse, making environmental management problematic. Existing monitoring relies heavily on "snapshot" data, due to access and other limitations, particularly during major flow events on large floodplains. Landsat TM/ETM+/OLI data can provide a relatively continuous record back several decades but dealing with large numbers of large data files is a challenge.

Complicated multiple-channel areas can be divided into landform-based units of relatively homogeneous geomorphology. Changes over time to individual channel inundation behaviour can be compared between similar landscape units to better identify whether the change drivers are local or regional. Positional and duration changes along transects can indicate a gradual or sudden alteration in upstream flow connectivity. “Ribbon plots” provide a tool to summarise decadal Landsat data and emphasise localised  temporary water features such as ephemeral waterholes.

One such landscape, the floodplain at the confluence of the Cooper Creek and Wilson River, has been divided into landscape units. Representative channels within these units, and also transects across the entire floodplain, have been defined. Inundation and vegetation responses along these paths have been summarised for the period 1986 to the present using NDVI and water indices derived from Landsat spectral data. Relationships between the physical landscape units and the inundation behaviour patterns have been examined. Specifically, anectotal evidence that anthropomorphic flow interruptions on the floodplain have altered the waterhole filling direction and persistence has been compared to climate and Landsat records.

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