Spatial Analysis of the Impacts of Urbanisation on the Health of Ephemeral Streams in Southeast Queensland Author Millington, Heidi Kathryn Published 2016 Thesis Type Thesis (PhD Doctorate) School Griffith School of Environment DOI https://doi.org/10.25904/1912/511 Copyright Statement The author owns the copyright in this thesis, unless stated otherwise. Downloaded from http://hdl.handle.net/10072/367358 Griffith Research Online https://research-repository.griffith.edu.au Spatial Analysis of the Impacts of Urbanisation on the Health of Ephemeral Streams in Southeast Queensland Heidi Kathryn Millington Master of Science Bachelor of Chemical Engineering Griffith School of Environment Griffith Sciences Griffith University Submitted in fulfilment of the requirements of the degree of Doctor of Philosophy April 2016 i STATEMENT OF ORIGINALITY This work has not previously been submitted for a degree or diploma in any university. To the best of my knowledge and belief, the thesis contains no material previously published or written by another person except where due reference is made in the thesis itself. Heidi Kathryn Millington i ACKNOWLEDGEMENTS I would like to acknowledge the academic and financial support of the Australian Rivers Institute. I would like to acknowledge the Australian Government for their financial support with an Australian Postgraduate Award Scholarship. I would like to thank my supervisors for their support and guidance. They are Professor Stuart Bunn, Professor Angela Arthington, Professor Bofu Yu and Dr Doug Ward. Thank you to Professor Yu for mentoring and editorial assistance. Thank you to Dr Ward for guidance on developing the ecological connectivity metrics of Chapter 5 and editorial assistance. I would especially like to thank my Principal Supervisor, Professor Bunn, for his guidance on research questions, ecological insights and editorial clarity, as well as Professor Arthington for her ecological insights, guidance on the selection of indicator species, and generous and articulate editorial assistance. Thank you to Brisbane City Council for provision of GIS data used in this research and the stream health data used in Chapters 5 and 6. Special thanks to Anne Simi. Thank you to my fieldwork assistants Miriam Paul, Peter Edwards, Andrew Bentley, Richard Grantham, Tim Jardine, Kuta Rovera, Anthony Smith, Andy Tidemann and Julie Lovell. Thanks to Dominic Valdez for helping me to source equipment. Thank you to Erin Peterson for guidance and mentoring in spatial analysis and statistics. Thank you to Julie Lovell, Geoff Heard, Peter Edwards, James Edmonds and Erin Kenna for additional editorial guidance. Special thanks to my colleagues and mentors for discussing ideas and concepts and providing suggestions on research directions and methods: thanks to Knox Lovell, Julie Lovell, Seth Wenger, Catherine Leigh, Fran Sheldon, Siti Amri and Peter Pollard. Thanks to James Edmonds and Gemma Tidemann for their friendship and support. ii DEDICATION To my daughters, Lucinda and Stella, and my grandfather, Winston iii ABSTRACT Aquatic ecosystems are vulnerable to threats from human activity. Numerous studies have shown that urban freshwater stream ecosystems are especially vulnerable to the intensity and complexity of stream health stressors associated with activities in the surrounding urban landscape. Scientists, government organisations and local volunteer groups are well aware of the deteriorating health of urban streams and are working towards understanding and managing the sources of stress on stream health. Improving the health of urban streams has the potential to provide local benefits such as biodiversity protection, enhanced ecosystem health, water purification, access to green space, scenic amenity and improved land values. While several important stressors have been identified in the Urban Stream Syndrome (elevated sediments, nutrients and contaminants, increased hydrologic flashiness and altered riparian and biotic assemblages) further research is required on the most important stressors and the mechanisms by which they impact stream health, especially in systems within dry climates where urban streams experience low flow conditions and flashy natural hydrology. Catchment-scale impervious surface has been identified in previous studies as a major driver of altered urban stream hydrology leading to degraded stream health. However, especially in drier climates, other aspects such as water quality and ecological processes associated with longitudinal and lateral connectivity have been identified as potentially more important stressors on urban stream health. This study on the ephemeral urban streams of sub-tropical southeast Queensland (SEQ) was designed to detect the relative importance to stream ecosystem health of catchment- scale impervious surface as well as reach-scale riparian cover. It also investigated the role of the ubiquitous stormwater piping found in urban areas and whether it influenced ecological connectivity, especially in terms of biota dispersal. Further, the influence of the areal extent of the study on the detection of the relative importance of different stream stressor metrics was considered. Reach, local and catchment-scale spatial (inverse-distance weighted and areal buffer) and non-spatial (lumped) land-cover metrics including several novel metrics relating to effective riparian buffers and in- stream ecological connectivity were generated in a geographic information system to represent land-cover stream stressors. A lumped land-use metric (population density) and various landscape metrics such as catchment extent were also considered. The investigations were carried out in two study areas: (1) a focus study of 30 sites along two highly urbanised catchments (Bulimba Creek and Norman Creek) within the larger iv study area, and (2) the larger study area consisting of 33 sites within multiple catchments of the Lower Brisbane River and surrounding coastal catchments. For water quality and biotic diversity and abundance, land-cover and land-use stream stressor metrics and additional landscape metrics were combined into a priori models that were fitted using generalised least squares and compared using the Akaike Information Criterion statistic. Model averaging provided further evidence to differentiate the importance of relatively similar metrics. Occurrence models for several native aquatic species were developed using generalised linear modelling and tested by comparing the Root Mean Squared Predictive Errors. The key findings of this study, which are relevant to the predominantly ephemeral urban streams in sub-tropical SEQ, were: 1) Catchment and local-scale impervious surface metrics were not strongly associated with variation in water quality and health indicators (macroinvertebrate and fish health indicators) compared with previous studies in temperate streams. This finding suggests that altered hydrology associated with impervious surface is also relatively less important in this region. 2) Reach-scale riparian buffer condition was relatively important in explaining variation in water quality and health indicators (maximum temperature and fish and macroinvertebrate diversity and abundance. 3) Metrics accounting for stormwater piping (effective riparian buffer metrics) were relatively important to explaining variation in diversity and abundance of macroinvertebrates (but not fish) and minimum dissolved oxygen, and they were relatively more important than lumped and distance-weighted catchment-scale impervious surface metrics in the study of smaller areal extent. This suggests that there is an influence of stormwater piping on stream health due to more than its association with impervious surface and altered hydrology. 4) When studied across a larger area (medium instead of small areal extent), the relative importance of catchment-scale impervious surface metrics for explaining variation in macroinvertebrate diversity and abundance in SEQ (as indicated by Stream Invertebrate Grade Number Average Level, SIGNAL2) was greater. The increased difficulty in differentiating the relative importance of various catchment-scale metrics in the medium areal extent study (due to multiple metrics having similar strengths of association with stream health), v suggests that localised effects are averaging out across larger assessment areas, as opposed to the larger-scale study better representing the scale at which stream health stressors are operating. 5) Several different ecological connectivity metrics designed to represent dispersal paths and habitat fragmentation, both in-stream and terrestrial, were relatively important in explaining variation in fish and macroinvertebrate diversity, abundance and occurrence and in several cases were relatively more important than catchment-scale impervious surface metrics. Different ecological connectivity metrics, as well as other land-cover and land-use stressor metrics, were relatively more important for explaining the occurrence of different taxa, a result that may be associated with different life history traits. Therefore such taxa may be useful indicators of the relative importance of ecological connectivity and other land-cover stressors in other studies. The thesis concludes with recommendations for policy and planning especially relevant to ephemeral, drier climate urban streams. Reach-scale rehabilitation and the protection of ecological connectivity should be combined with traditional water sensitive urban design approaches. The intermittent