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

River Styles assessment and geomorphic sensitivity of the Waipā River Catchment, Aotearoa New Zealand (#100)

Nicole Wheeler 1 , Will Marson 2 , Michael Pingram 3 , Bruno David 3 , Jon Tunnicliffe 4 , Gary Brierley 4 , Ben Pearson 1
  1. Hydrobiology, Auchenflower, Queensland, Australia
  2. Aerialsmiths New Zealand Ltd, Auckland, New Zealand
  3. Waikato Regional Council, Hamilton , New Zealand
  4. School of Environment, The University of Auckland, Auckland, New Zealand

River form within New Zealand’s North Island volcanic landscapes is strongly conditioned by geologic structure and large-scale reconfiguration of the drainage system in response to volcanic episodes. Rivers have been further conditioned historically by widespread drainage of wetlands, straightening of meandering river courses, reinforcement of banks and stop-bank emplacement. Waikato Regional Council, Hydrobiology QLD Pty Ltd, Aerialsmiths New Zealand Ltd and The University of Auckland completed a River Styles assessment of the Waipā River Catchment, the first known River Styles assessment carried out for government in Aotearoa (Marson, Wheeler & Brierley, 2021). This was to provide council with a geomorphic baseline of their catchment, as well as a catchment-scale sensitivity analysis, highlighting reaches that were more sensitive to change to better prioritize management initiatives. Building on this sensitivity analysis, GIS tools were used to analyze stream power and historic imagery time series to examine the relative capacity for river adjustment along 3,000 km of channels (3rd Strahler order and greater) in the catchment. Only 3% of the studied river length showed any indication of significant planform adjustment since the 1950s. These dynamic sites were generally gravel-bed reaches in high energy, laterally unconfined settings within the piedmont zone. Elsewhere, the river was constrained by bedrock, valley fill terraces, and legacy effects induced by anthropogenic margin-controls. From the perspective of efficiently scoping sites that may hold promise for dynamic habitat evolution and ecosystem renewal, this work provides catchment managers with a basis in which to prioritize management initiatives.

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