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

Working with river process in managing sediment flux from the Kourawhero Catchment into Kaipara Harbour Aotearoa New Zealand (#66)

Jacqui McCord 1 2 , Jack Clothier 1 , Jon Tunnicliffe 1 , Gary Brierley 1 , Hannah Brightley 3 , Sarah Nolan 3 , Scott Speed 3
  1. School of Environment, University of Auckland, Auckland, New Zealand
  2. Morphum Environmental, Newmarket, AUCKLAND, New Zealand
  3. Auckland Council, Auckland, New Zealand

A major catchment-scale rehabilitation initiative is underway to address sediment flux in river systems that drain into Kaipara Harbour, northwest Auckland, Aotearoa New Zealand. Our study area, the Kourawhero Stream, drains approximately 5% of the catchment but has been identified as a key sediment hotspot. This is an unusual river system in New Zealand, behaving as a fine-grained cut-and-fill river system. Unless management programmes work with the distinctive properties of such a river, they are unlikely to be successful.

This work reports on collaborative investigations by researchers at the University of Auckland and river managers/practitioners at Auckland Council. It uses the River Styles Framework, combined with field investigations, landscape mapping and modelling analyses to assess river processes in the Kourawhero and provide scientific guidance to inform management practices.

The Kourawhero Catchment is a fine-grained cut-and-fill river system. Geologically-induced accommodation space, alongside long-term tectonic uplift has influenced the base level of the river. Subsequent incision and ongoing headcut erosion has released large volumes of sediment from this system, which is efficiently conveyed through to the harbour.

Unless management practices work with river processes and respect river diversity in their individual catchment setting, they are unlikely to be effective. Auckland Council are developing an approach for ‘Geomorphologically Effective Management Solutions’ (GEMS) to work with river processes to address concerns of sedimentation from rivers into the Kaipara Harbour. Use of the River Styles Framework presents opportunities for geomorphic analyses to support such applications.

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