Assessing the value of a geomorphic toolbox to assist with determining ecological health of wadable streams within the Waikato Region : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Geography at Massey University, New Zealand
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Date
2020
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Massey University
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Abstract
Ecological measures such as quantification of taxa and chemical indicators are well established as tools for assessing river health, but the geomorphic component is often left out despite forming the template on which all other processes occur. To address the missing geomorphic component in monitoring river health, this research focused on framing river health within a geomorphic context and formulated a Waikato Region-specific geomorphic toolbox to be integrated with existing river health monitoring, providing a more holistic understanding of rivers in the region. Six indicators were chosen to assess geomorphic condition and develop a toolbox: riparian zone, wood, bank erosion, particle size, connectivity and geomorphic units. Reference conditions were established for each site based on ‘minimally disturbed’ conditions. Qualitative and semi-quantitative techniques for assessing each indicator were outlined and tested against six monitoring sites – four ecological reference state and two non-reference state – within the Waikato Region using desktop based ‘apriori’ methods, as well as in-field monitoring. Assessment outputs included a qualitative proforma of each stream and a scoring mechanism to provide comparable results of each streams. Streams were given an assessment level from ‘Excellent’ to ‘Very Poor’ depending on their geomorphic quality. Four reference sites were assessed as ‘Excellent’, while the two non-reference sites were assessed as ‘Poor’ for geomorphic quality. Comparisons to ecological monitoring data of the same reaches showed a relationship between ecological and geomorphic health, such as the excellent fish and MCI scores corresponding with ‘Excellent’ geomorphology. However, proximity to the coast can skew fish indicators due to the diadromous nature of many native New Zealand fish; whilst the Whangarahi Stream was considered ‘Poor’ for geomorphic health, it was inhabited by an order of magnitude more eels than any other reach assessed. The use of reference conditions is integral to a well-functioning geomorphic toolbox, although further exploration is needed around whether reference conditions should represent ‘minimally disturbed’ or ‘best attainable’ condition given existing land use patterns. Inclusion of more encompassing geomorphic unit indicators, as well as bed structure would strengthen the toolbox. The geomorphic toolbox was created to provide meaningful and comparable data for assessing geomorphic health in a time- and cost-efficient manner, which has been achieved. Subject to further testing and refinement of variables to maintain relevance to a range of geomorphic contexts, the toolbox is considered adequate for inclusion into State of the Environment reporting structures for the Waikato Region.
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These copyrighted Figures were removed: 1 (=Fryirs & Brierley, 2013 Fig 1.1), 2 (=Davies et al., 2010 Fig 1), 3 (=Fuller et al., 2019 Fig 3), 4 (=Baron et al., 2002 Fig 1), 5 (=Wohl et al., 2019 Fig 1), 6 (=Poole, 2010 Fig 4), 10 (=Corenblit et al., 2015 Fig 4), 11 (=Thorp et al., 2006 Fig 3) & 12 (=Fryirs, 2003 Fig 2). Figures 8 & 9 (=Lake, 2000 Figs 8 & 1) are re-used under license from the Copyright Clearance Center.