Resource Management and Geography - Theses
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ItemGravel-bed river behaviour: modelling and analysis of process feedbacks over spatio-temporal scales( 2021)Alluvial rivers arise through process interactions between water and a deformable boundary. These processes are poorly understood in gravel-bed rivers as they are difficult to measure, and are often described using simple conceptual models. Perhaps the simplest is the 'fluvial trinity' which describes the feedback between sediment transport, morphology, and hydraulics. There are two aspects of channel dynamics not explicated by this model: (1) the spatial distribution of channel feedbacks, and (2) interactions between processes across spatial-temporal scales. This thesis examined the effect of these two aspects using a recirculating stream table, from which conceptual frameworks and analytical tools were developed. First, I modelled the response of a channel to successive increases in discharge and identified stage-dependent feedbacks that controlled the adjustment of the system towards a steady-state. Notably, at low flows, transport capacity was modulated by the spatial concentration of shear stress and channel deformation was controlled by larger-than-average grains. The following chapters focused on two components of the fluvial trinity. I combined recent advances in fluid dynamics, statistics, and remote sensing to estimate how roughness length varied across different physical scales. The novel technique provided an intuitive representation of how morphology and hydraulics vary across different scales and affirmed the importance of bar-scale roughness in pool-riffle settings. I evaluated the performance of 1D and 2D bedload transport functions under high relative shear stress conditions. The results clarified that although the spatial distribution of shear stress may be required to predict transport under low stresses, 1D simplifications may be effective under high stresses. Despite being similarly accurate, the 1D and 2D approaches provided substantially different estimates of critical dimensionless shear stress, suggesting that the estimate and interpretation of critical shear stress may depend on whether it is averaged or considered a distribution. Finally, I reviewed hierarchical conceptual frameworks based on ideas of self-organisation or 'emergence' and their potential application to explain the relationship between processes occurring across different spatio-temporal scales within fluvial systems. These conceptual frameworks provide testable hypotheses about the relationship between process scales and may have implications for understanding sediment transport and approaching physical modelling of rivers.
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ItemPatterns and drivers of vegetation change in coastal dunes( 2022)Coastal dunes are dynamic and episodically respond to changes in climate, human disturbances, landforms and biota, resulting in varying dune mobility ranging from completely mobile to fully stable. Dune mobility also varies at different temporal-spatial scales, dominated by different drivers. The response of dune morphologies to changes in boundary conditions is non-linear, usually with a lag effect. In this thesis, the decadal change in dune mobility and primary drivers, as well as the precise trajectory of vegetation expansion during dune stabilisation were examined at different scales (the global, regional, and individual dune site). In the past century, the overall changes in climate and coastal management are pushing coastal dunes toward a more stable status at a broad scale. Specifically, there was a worldwide trend of dune stabilisation in 1870 - 2018 that 93% (164 out of 176) of the studied sites showed an increase in vegetation cover and urbanisation expansion. The global pattern of dune stabilisation was mainly caused by 1) land-use change, 2) dune stabilisation projects, 3) decline in sediment supply from the coast to the dune system, and 4) changes in climate and storms. A similar stabilisation trend was observed in Victoria, southeast Australia, that dune vegetation increased by 23% (from 61% to 84%) from the 1960s to 2020, mainly resulting from extensive coastal management (e.g., dune stabilisation projects by marram grass planting and protection from various disturbances by national and coastal parks) and a favourable climate condition (e.g., increasing temperature and decreasing windiness). At a small scale (e.g., specific dune site), local drivers (either climatic-induced disturbance or human interventions) can be the most critical factor of dune mobility change. A loss of dune vegetation only occurred in areas with retreating coasts (e.g., the coast of Inverloch and parts of the 90 Mile Beach), caused by storms, sediment deficit, or rising sea levels. The Woolamai dune field has shifted from nearly bare (with < 5% vegetation cover) to a new quasi-equilibrium state, being almost fully stabilised by vegetation (> 80%) from 1939 to 2020, mainly driven by a revegetation program over 1976 – 1988. These examples indicate the determining role of local drivers in changing vegetation cover and shifting dune mobility at the specific dune site scale. The spatial-temporal expansion of vegetation over the course of dune stabilisation are mainly regulated by the topography of the dune field, which can determine water content and the degree of shelter for vegetation establishment. Pre-existing vegetation also plays an important role in later expansion, likely by modifying soil nutrients and surface roughness, and providing the presence of seeds for further floral initiation and expansion. The major conclusion of this thesis is global climate change has provided conditions for enhanced dune stability across the globe. This has acted to enhance management activities aimed at increasing vegetation cover. Human activities, both intentional and unintentional are the drivers of dune mobility on the modern coast.
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ItemSynchrony and precise timing of millennial-scale climate events during the last glacial period based on speleothem palaeoclimate records( 2022)The climate of the last glacial period (115,000 – 11,500 years ago) is characterised by a series of abrupt climate changes, termed millennial-scale climate events, that are one of the best examples of naturally occurring abrupt climate change. These events are best recorded in Greenland ice cores, as well as marine and terrestrial records from a wide range of climate zones. However, many unknowns remain regarding the events, including whether they occurred synchronously between different climate regions, the precise timing of the events and the underlying cause. The objective of this thesis is to advance our understanding of millennial-scale climate events through the use of speleothem palaeoclimate records. Speleothems, cave deposits such as stalagmites, can provide high-resolution and precisely dated records of millennial-scale climate events from a range of climate regions. This thesis is approached through two complimentary projects. The aim of the first project is to assess if millennial-scale climate events occurred synchronously between different regions. Sixty-three published, precisely dated speleothem records were compiled, and the timing of the onset of interstadial conditions (the warming component of the events in Greenland) was compared between records. It is found that the events occurred synchronously between Greenland, Europe and the Mediterranean, and the Asian and South American Summer Monsoon regions. This finding supports the long held, but previously untested, assumption of synchrony in the timing of millennial-scale climate events, and suggests that the events were rapidly propagated between these regions through atmospheric teleconnections. A key output of this project is the development of the SIOC19 data set of precise radiometric constraints for the timing of the onset of interstadial events based on the compiled speleothem records. This data set enables the accuracy of non-radiometric chronologies to be evaluated. The second project of this thesis investigates the timing and expression of millennial and sub-millennial-scale climate events during the early last glacial period. This time period is less well represented by existing speleothem records, and exhibits a diversity of sub-millennial-scale climate variability which is not well studied outside of Greenland. Five new speleothem palaeoclimate records are assembled from Saint-Marcel and Orgnac Caves in Ardeche, south-east France, that collectively span the period from 127 to 87 ka. The replicated d18O and d13C time series provide a comprehensive record of millennial and sub-millennial scale climate variability, which mirrors events observed in the Greenland ice-core record, suggesting a strong climate coupling between south-east France and Greenland. Interstadial periods are interpreted to be associated with an abrupt increase in soil and vegetation activity, reflecting an increase in temperature, and an increase in the dominance of precipitation from the Atlantic. Variation in Mg/Ca, Sr/Ca and (234U/238U)0 is also observed across the main stadial-interstadial transitions, the interpretation of which is explored. A decoupling between temperature and precipitation changes over some sub-millennial events is found to occur, suggesting the events are distinctly different to the main millennial-scale climate events. A stacked chronology is produced, based on 130 individual uranium-thorium ages, that provides a well constrained chronology of the early last glacial period. Comparison is made between the timing of the onset of interstadial events in Greenland, the Ardeche speleothems, and in the SIOC19 data set. Overall, this thesis provides key insights into the synchronicity, precise timing and regional expression of millennial-scale climate events, that is useful for validating climate model output and testing hypotheses on the underlying cause of the events
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ItemWatering the ‘New Beijing’: Chinese ecotopia, Xiong’an and its water security( 2022)This thesis aims to examine the purpose-built Chinese ecotopia-Xiong’an from the perspective of sustainable development and efficient urban water management. Three research questions were addressed to achieve this aim: 1) What are the water-related justifications of Xiong’an? 2) How to secure water for Xiong’an? 3) to what extent is urban development for the new city informed by questions of water availability? Using a combination of quantitative and qualitative approaches, the three research questions addressed the water security perspectives involved in designing and constructing the new ecotopia. The thesis argues that the current eco-philosophy of building a city to mark the sustainable transition in China relies on using large-scale infrastructure projects, thus creating a paradox at local, regional scales that questions the very idea of water security. The analysis concludes that in contrast to the expectations from planning, Xiong’an cannot alleviate Beijing’s water pressure as expected by the central government. Rather than applying a water-saving urban design, in practice water uses pushed Xiong’an forward on its unsustainable path. Specifically, the existing infrastructure efforts, both geological and water conservancy, made this ecotopia a high cost, high expected maintenance and highly fragile project. The making of Xiong’an through centralized urban planning is contrary to the expectation of providing broad implications to other cities; Xiong’an is instead using its political importance to export water insecurity and transfer its unsustainability down through the urban hierarchy to other cities. The thesis fills several research gaps in urban geography through two lenses: one is the urbanization model in developing countries, the other is the urban water security. Water is the window used in the thesis to interpret China’s sustainable transition proposal and its eco-philosophy practice to create a future city through a centralized planning and water governance regime.
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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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ItemExamining the role that vegetation plays in inducing the deposition of fine sediment in Southeastern Queensland river corridors( 2020)Southeastern Queensland river corridors have a fine sediment problem, causing temporary water shortages to the Brisbane Metropolitan area during Cyclone Oswald in 2013, as well as edging Moreton Bay closer to a permanently turbid state, threatening seagrass, corals and important fisheries. One possible solution is revegetating rivers corridor in order to trap fine sediment and reduce its delivery into water supply reservoirs and Moreton Bay. This thesis examines the influence of shrubby vegetation on the deposition of fine sediment on benches and floodplains along rivers. Most researchers just assume that it is very effective at doing so and some argue that riparian shrubs world wide have actually evolved specific traits to induce the deposition of fine sediment and act as ‘ecosystem engineers’ (Corenblit et al., 2015). In doing so these ecosystem engineer plants construct fine sediment landforms in a river, and thus, create their own ecological niches. However, biogeomorphic ecosystem engineering has never been described in the subtropics, nor have studies illustrated that the above ground biomass density of riparian vegetation can actually induce the deposition of fine sediment during flows. Furthermore, though conceptual frameworks for the distribution of different biogeomorphic interactions have been developed (Gurnell et al., 2016), this framework has not been applied quantitatively to explain the distribution of biogeomorphic interactions due to the flow regime, geomorphic context, and biogeomorphic traits. Additionally, the construction of fine grained landforms by vegetation is dependent on the supply of fine sediment, and no studies on the subject have examined the patterns of incoming SS on the effectiveness of floodplains and vegetation as fine sediment filters. My thesis addresses these gaps outlined above, where I test the validity of this ecosystem engineering model in Southeastern Queensland river corridors for two rheophytic shrub/ tree species, Meleleuca bracteata and Casuarina cunninghamiana, in order to assess its use as a management strategy for reducing fine sediment yields from catchments. Specifically, my thesis addresses the following research question: How do the major drivers of the process of vegetated induced deposition dictate the types and spatial distribution of biogeomorphic interactions in Southeastern Queensland river corridors? To address this overarching question with the following research questions: 1. How does the supply of sediment and frequency of flow dictate the part of the river corridor where vegetation is most likely to induce sedimentation, and reduce end of catchment yields? 2. Under what flow conditions can riparian shrubs and trees in SEQld induce the deposition of fine sediment due to their above ground biomass density, and at what part of the river corridor do these conditions occur most frequently? 3. What kinds of bigeomorphic interaction occur most frequently in SEQld macrochannels, and where do these interactions occur most often? These three questions are addressed in three empirical chapters (Chapters 3, 4, and 5). The capacity of vegetation to trap sediment depends on how sediment is delivered to the floodplain. Analysis of an exceptional data set of suspended sediment from 19 streams in SE Qld demonstrated that the proportion of total annual sediment yield moving onto the floodplain in floods varies dramatically between catchments, from 5% to 95%. Hysteresis could increase or decrease the proportion of an event sediment load moving onto the floodplain by 10 - 20%, but the larger the flood the smaller the hysteresis. This is one of the most comprehensive analyses of this basic floodplain process available. I then turned to the probability of inundation of a vegetation patch, as well as the ability of that patch to influence suspended sediment transport and deposition. I applied hydraulic theory to Terrestrial LiDAR scanner derived measurements of vegetation density, in order to estimate the threshold shear stresses for within-patch deposition of suspended sediment. I found that rheophytes with patch averaged densities greater than 0.2 can influence hydraulics enough that they could induce deposition of silts in flow conditions that would otherwise only deposit gravels in the absence of vegetation. lend- ing process based evidence that vegetation can trigger the deposition of suspended silts when establishing on flow regimes where medium gravels would normally be deposited. Further, data from 21 stream gauges suggest that vegetation could induce deposition at between 15 to 25 % of the total inset bank height, providing a process based estimate of the critical zone for biogeomorphic interaction (Gurnell et al., 2016), namely the height above the thalweg where vegetation induced deposition is most likely to occur. Although vegetation can induce deposition I did not find compelling evidence for the proposition that these plants create ecological niches by converting gravel bars into fine- grained landforms. Out of 103 trees that I excavated on floodplains, only 7 (7%) showed this pattern. In the rest of cases the plants established on a fine grained surface, and further deposition was also fine grained. Thus, these plants appear to be opportunists rather than engineers. The peak in both burial depth, and deposition rates occur between 30 - 100 % of the inset bank heights, implying that the the actual critical zone for deposition is broader, and higher up the bank than the process based estimate made earlier in chapter four. The findings of this thesis show that riparian vegetation can induce the deposition of fine sediment, but the proportion of catchment sediment yield will vary enormously between catchments. Where plants do establish coarse bars, they can occasionally induce the deposition of a new floodplain. However, in the reaches of SEQld studied in this thesis, patches of vegetation are more likely to establish as a consequence of existing fine sediment deposition than be the cause of that deposition, implying that these riparian species are opportunists, before they become biogeomorphic engineers.
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ItemSpatiality and materiality in knowledge controversies: the co-production of expertise with socio-material order( 2020)This dissertation examines knowledge controversies and the role of spatial and material forces in the production of expertise. The focus is on the spatial and material aspects of expert knowledge production, how they shape the performance of expert knowledge, and what this means for analyses of decision-making power. The core problem being addressed is the under-interrogation of spatiality and materiality as it relates to the production of expertise in knowledge controversy events. The aim is to expand the explanatory potential of the literature by incorporating spatiality and materiality into analyses of expertise. The fieldwork concerned a knowledge controversy event that centred around the White River in the Southern Carpathian mountain ranges of Romania. This river captured the attention of a coalition of NGOs in Romania known as the Natura 2000 Federation Coalition of Romania. They brought legal action against an arm of the Romanian state who granted a proposal to develop a micro-hydropower project on the river. The research then analyses the spatiality and materiality of expert knowledge and its role in shaping the case of the White River as a knowledge controversy event. My research questions focus on how spatial and material forces are garnered in the production of expert knowledge, and how this influences the exercise of decision-making power by experts in knowledge controversy events such as the White River case. My approach to addressing these questions assembles work in knowledge controversies, STS, materiality, spatiality, geographies of science, and critical legal geographies literatures. In addressing my research questions, I argue that experts need to create, maintain, and defend space in order to underpin their knowledge claims and related claims to decision-making power. This conception is contrasted with arguments that assume the primacy of the socio-material rubric, and given that condition, the pre-eminence of ‘socio’ forces in a context of ‘socio-material’ order. My critique contributes to spatiality, materiality, STS, and knowledge controversies literatures with an analysis of the experts attached to the White River controversy. In particular, my analysis foregrounds the spatiality and materiality of expert knowledge practices to illustrate their influence in knowledge controversy events. I do this by outlining various forms of expertise involved with the White River case (e.g., law, science, government, NGO) to examine the intersection and contestation of knowledge production in spatial and material terms. Ultimately, I argue for a ‘space creating analytic’ to be applied to knowledge controversy analyses that utilises the explanatory power of the spatiality and materiality of expertise.
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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.
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ItemExperiencing and Adapting to Heatwaves: A Study of Bangladesh-Born Migrants in Victoria( 2020)Climate change is a critical concern in Australia and globally. Anthropogenic climate change will contribute to increasing intensity and frequency of heatwaves. People view and respond to heatwaves in many ways, depending on their awareness, expertise, access to resources and geographic location. Previous experience of climate extremes is a critical factor in shaping how people perceive risks and adapt to reduce the impacts on their lives and livelihoods. In the past decades, many studies have focused on heatwaves, heat-health impacts including mortality and morbidity, and heatwave adaptation and mitigation. However, limited research reflects on culturally and linguistically diverse (CALD) populations and migrants in relation to heatwave experiences and adaptation. Advancing understanding of the impacts of heatwaves on migrants' lives, and the significance of their cultural beliefs and past experience of heatwaves, can provide insight into heatwave adaptation. In particular, migrant communities with heatwave experience may have potential to respond effectively to heatwave events at the resettlement site. This study aims to understand the experience of heatwaves among members of a migrant community in a site of settlement, namely Bangladesh-born migrants in Victoria. It investigates risk perception around heatwaves, the impact of heatwaves on daily lives, and coping techniques used by this cultural community. Considering the diverse cultural background and experiences of the participants, this study also examines whether and how their environmental knowledge, cultural beliefs and previous adaptation experience influence their ability to adapt to heatwaves in Victoria. In addition, this study discusses some of the major challenges confronting this population in applying heatwave adaptation strategies. A mixed-methods approach comprising both qualitative and quantitative research was used to conduct this study. The data collection instruments consisted of a semi-structured interview protocol and a survey questionnaire. One-on-one, semi-structured interviews were conducted with 20 participants, who were purposively chosen from five Local Government Areas (LGAs). The survey data (n=393) were collected from five LGAs in Victoria using a three-stage cluster sampling technique. A four-part survey questionnaire involving Heatwave Risk Perception, Heatwave Adaptation Strategies, Cultural Beliefs towards Heatwave Adaptation and Barriers towards Heatwave Adaptation was developed to assess the experience of participants. The 33 item Heatwave Adaptation Strategies measure was used to identify heatwave adaptation techniques used by participants; participants were asked to respond to these 33 items both in relation to adaptation measures used previously in Bangladesh, and currently in Victoria. The questionnaire used a six-point Likert type scale for recording participants' self-reported responses. Quantitative data were processed and analyzed using Statistical Package for Social Science (SPSS) version 26. A descriptive analysis (mean and standard deviation) was undertaken to report the overall results, while advanced inferential statistics (i.e. t-tests & multiple regressions) was used to identify several predictor variables and their association with each other. The findings of the study are presented in chapters four and five. In chapter four, the analysis of the interviews yields the Bangladesh-born Victorian migrants' own explanation on their understanding of heatwaves, their risks to everyday life, and a range of challenges and adaptation measures to cope with this climate extreme based on their current and previous heatwave experience. The semi-structured interview protocol was developed to gain an in-depth understanding of participants' pre- and post-migration heatwave experiences and challenges. A hybrid method of thematic analysis, comprising both inductive and deductive approaches, was used to analyse interview data. The quantitative results are presented in chapter five. The results show the extent to which the participants perceived heatwave risks, their use of adaptation strategies, cultural beliefs, and barriers towards heatwave adaptation. For instance, this migrant community perceived a high frequency of heatwave risk (M=4.60, SD=1.22). The stepwise multiple linear regression results also demonstrate the significant predictors of heatwave adaptation strategies (HAS) in Victoria. Both qualitative and quantitative findings suggest that lack of access to information about heatwaves and their consequences is one of the major challenges for participants in adapting to heatwaves in Victoria. In addition, both qualitative and quantitative findings add nuance to understanding migrants and their adaptive capacities in coping with climate extremes in the host country. The study may provide useful insights for relevant planning organisations and government officials engaging in climate change adaptation planning and striving to reduce the negative impacts of heatwaves across all members of the community.
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ItemEvaluating barriers to dispersal: weirs and tributaries in the montane rivers of the Australian Alps( 2020)Dispersal involves the movement of individuals between established populations or colonisation of uninhabited areas and is a key organising process underpinning patterns in populations and communities. Dispersal is a fundamental component of metapopulation and metacommunity theory, central to explaining the underlying the patterns of abundance and distribution of species, both spatially and temporally. Furthermore, dispersal is a main determinant of community assembly, governing how communities are constructed and maintained through immigration. Barriers that limit or prevent species from dispersing to a location can have a major influence on population dynamics and how communities assemble. In a restoration context, this can result in delayed or poor restoration outcomes due to a lack of dispersing colonists preventing colonisation. In freshwater environments, one key hypothesis describing how dams and weirs affect rivers is that they disrupt longitudinal connectivity, fragmenting river ecosystems, potentially limiting dispersal of biota along rivers. In this thesis, I asked three main questions: 1) Are there natural barriers to dispersal in advective systems? 2) Do artificial barriers hinder dispersal more than natural barriers? 3) Do artificial barriers constrain dispersal in ways that affect population and communities, especially community assembly? The study focused on rivers located mostly within Kosciuszko National Park, in the Snowy Mountains region of south-east Australia. Many rivers in this area are affected by the Snowy Mountains Hydro-electric Scheme and associated culverts, weirs and dams, which capture and divert numerous alpine and montane streams, severing flow connections between much of the Snowy River catchment and its headwaters. First, I tested how species dispersal between suitable habitats was influenced by the characteristics of the intervening matrix of unsuitable habitat. Specifically, I examined whether stream insect drift was constrained by natural river features, potentially limiting connectivity within rivers. I found that natural, slow moving pools may limit the connectivity of benthic invertebrate populations in rivers by reducing drift rates between riffle habitats. Furthermore, I determined that the hydraulic conditions within a pool limit drift dispersal and total distance between riffle habitat patches was not an important factor in limiting dispersal via drift. Secondly, I tested whether species dispersal was constrained by a human-made barrier, potentially limiting connectivity between populations more than natural landscape structures. In a natural river system, I studied whether a weir and associated pool reduced the drift rates of insects to a greater degree than natural pools. This component addressed a major knowledge gap about the effect of weir structures on downstream dispersal of stream biota. The weir consistently reduced numbers of drifting insects for 3 of 4 study taxa, exceeding the reduction of drifters in natural pools. The morphology of the weir pool was substantially deeper and wider and slower than the majority of studied natural pools. The combined effects of much lower average water velocity, multiple large low velocity areas within the weir pool and the weir wall were likely to be central causes of the reduction stream insect drift through the weir. Lastly, in a multi-year study, I tested whether and how the removal of dispersal constraints affected community assembly in new habitats and whether changed dispersal can alter existing communities. In this study, I investigated the patterns and mechanisms of freshwater invertebrate community assembly after the reintroduction of water to 2 streams downstream of weirs that were previously dry for over 50 years. Colonisation of the newly formed habitat in the tributaries downstream of the weirs was rapid and strongly influenced by dispersal via drift from upstream. Even with some dispersal constraint via reduced drift rates, the new communities rapidly resembled unimpacted communities that were the source of colonists. In the regulated rivers, a reduction in environmental constraints had a much greater influence on the trophic structure of established communities than increased dispersal from the newly formed community in the tributaries. Collectively, this research has overturned important, pre-existing assumptions about dispersal in advective systems by identifying and quantifying the influence of different types of barriers on movement and the effect of altered dispersal rates on community assembly. This information can inform the development of river restoration strategies in rivers affected by weirs and dams and elucidate how and why restoration measures may have been unsuccessful in the past.