Resource Management and Geography - Theses
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ItemGeomorphology of small arid zone streams in the Pilbara (Western Australia) and implications for design of mine river diversions( 2022)This thesis is concerned with an under-recognised human impact on rivers: river relocations (called diversions herein), in which a section of river is diverted into an entirely new channel for part of their length. Relocated channels present a consistent set of physical and ecological challenges, often related to accelerated erosion and deposition. I develop a classification of river diversions and present a series of case studies that highlight some of the key issues with river diversion construction and performance. Changes to channel dimensions and materials, alongside changes to flow velocity and channel capacity, lead to a consistent set of problems, such as heightened erosion or deposition, hanging tributaries, vegetation loss, water quality issues, and associated ecological impacts. Diversion channels often suffer engineering failures. This thesis reviews river diversions as a global phenomenon, and then focuses on a major class of diversion in which streams are diverted around mine sites. Mining river diversions are constructed to avoid flooding of the mine site and to allow access to ore. During mine operation, river diversion channels are designed to convey large floods with an emphasis on channel stability and effective flow conveyance. After mining has ceased, the expectation is increasingly that river diversion channels eventually behave more like a natural river system and imitate characteristics of surrounding watercourses. However, in many regions there is limited guidance on how to incorporate the natural geomorphic and environmental attributes of the neighbouring watercourses into these diversion designs. The Pilbara region in Western Australia has many open-pit mines and river diversion channels relocating small headwater channels but generally there is a poor understanding of the regional watercourses within this semi-arid landscape. I examine the geomorphology of small arid zone streams in the Pilbara to provide improved guidelines for geomorphic criteria for river diversion designs. This work also fills a basic knowledge gap around the geomorphology and hydrology of headwater channels in the dryland Pilbara. Geomorphic processes occur on a continuum of timescales, where landforms are influenced by a series of imposed controls (e.g. climate and geology) and flux controls, those that adjust over geomorphic timescales (e.g. vegetation, bedforms). After a review of river diversions in general, this thesis uses an integrated approach to combine geomorphology, hydrology, hydraulics and ecohydrology to address three key questions about Pilbara streams: 1) What is the geomorphology of headwater streams in the Pilbara and what are the key sedimentological, hydrological, and hydraulic controls? 3) What are the conditions required to allow natural channel morphology to develop within river diversion channels? 4) How long does it take for a target morphology to develop in river diversion channels? Based on extensive field surveys, this thesis develops the first classification of dryland headwater channels in the Pilbara, describing the variation in channel form and the range of geomorphic features found in them. Vegetation contributes 35-54% of channel roughness (resistance) in these dryland channel types and can increase channel roughness by 110% in low-slope anabranching sandy channels. This thesis highlights the importance of incorporating appropriate roughness in diversion channels through the presence and distribution of vegetation. To better understand sediment flux in these catchments, I assessed the long-term denudation within catchments using cosmogenic nuclides (26Al and 10Be) using a nested catchment approach to quantify dominant sediment pathways from slopes to larger channels. Denudation rates in the Upper Fortescue catchments are among the lowest recorded between 0.94 - 4.04mMyr-1 and channel sediment have a complex exposure history. This is attributed to sediments undergoing prior-burial for a minimum of a few hundred thousand years, and/or b) sediments being largely derived from below the surface from cliff faces through spalling and slab fragmentation. This thesis is the first comprehensive geomorphic study of headwater channels in the Pilbara, generating a series of guideline hydraulic values for different channel types. Two-dimensional hydrodynamic modelling was used to estimate peak flood flows in lieu of adequate stream gauging. Before this research, there have been limited attempts to determine the best regional flood frequency estimates for small headwater catchments in the Pilbara, leading to confusion about the most appropriate approaches to calculate peak discharges. Finally, the thesis integrates the new geomorphic knowledge to produce a series of guideline hydraulic criteria for river diversions across a range of flood intervals. The developed hydraulic guidelines for the different channel types can help engineers and managers design a permanent river diversion that replicates conditions found within local headwater channels. The results also indicate a wide range of hydraulic values within each channel type, highlighting the importance of localised fluctuations in velocity, streampower and basal shear stress in maintaining channel form and complexity.
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ItemTurbulence, habit and desire: life after two coal mine closures( 2020)This thesis investigates the experiences of workers and their families as they navigate disruptions to everyday life caused by workplace closure and job loss. Situated in the boom-and-bust world of extractive industry, it draws on qualitative fieldwork at two recently closed coal mines in Australia and China to explore the twists and turns of life after loss in restructuring economies. Picking up people’s lives several years after the mine closures, this thesis traces the cascading chain of changes catalysed by the event of closure. It explores how circumstances of life come to press upon bodies in the wake of loss, and how these intensities can come to reshape how people experience the world. It ultimately asks how people might weather the crisis of loss such that they regain a sense of life as an ‘ordinary’ timespace, reorienting from the past to the future. To do this, this thesis approaches loss as a non-relational force of interruption, showing how loss decomposes existing relations and exposes people to an unknown present. Drawing on postphenomenological theories of bodily change, it then tracks the shifts in concerns, anxieties, and orientations that emerge in this timespace of vulnerability and exposure. These processes of change are explored through three empirical chapters on the forces of turbulence, habit and desire. Turbulence shows how loss can bring ordinary life into disorder, leaving people exposed to the intrusions of unfamiliar and often unmanageable conditions. Habit suggests how melancholy durations of life can redraw everyday existence, allowing bodies to pick up different lines of the past to make sense of the present. Finally, desire describes how encounters after loss might begin to mobilise processes of repair, reorienting people from a lost past towards an unfolding future. By examining the relationship between self and other in the constitution of subjectivity, this thesis shows how transformations of the subject can come about through affective intensities that fold otherness into the self. It contributes to understandings of affect, embodiment, and relationality in geography, addressing how the turbulent circumstances of life after loss can speak to tensions in geographers’ understandings of connection and disconnection, presence and absence, relation and non-relation, activity and passivity. By focussing on how people come to live on after loss, this thesis moves beyond the melancholic tendencies of existing literatures on loss to foreground incipient processes of corporeal transformation. Its thrust is thus consolatory: it aims to recognise the gaps and tears that accompany ends, whilst refusing to forgo the vital and affirmative possibilities of life after loss.