Papers by Robbi Bishop-Taylor
Remote Sensing
Accurately mapping the boundary between land and water (the ‘waterline’) is critical for tracking... more Accurately mapping the boundary between land and water (the ‘waterline’) is critical for tracking change in vulnerable coastal zones, and managing increasingly threatened water resources. Previous studies have largely relied on mapping waterlines at the pixel scale, or employed computationally intensive sub-pixel waterline extraction methods that are impractical to implement at scale. There is a pressing need for operational methods for extracting information from freely available medium resolution satellite imagery at spatial scales relevant to coastal and environmental management. In this study, we present a comprehensive evaluation of a promising method for mapping waterlines at sub-pixel accuracy from satellite remote sensing data. By combining a synthetic landscape approach with high resolution WorldView-2 satellite imagery, it was possible to rapidly assess the performance of the method across multiple coastal environments with contrasting spectral characteristics (sandy beach...
Estuarine, Coastal and Shelf Science
The intertidal zone represents a critical transition between marine and terrestrial ecosystems, s... more The intertidal zone represents a critical transition between marine and terrestrial ecosystems, supporting a complex mosaic of highly productive and biologically diverse habitats. However, our understanding of these important coastal environments is limited by a lack of spatially consistent topographic data, which can be extremely challenging and costly to obtain at continental-scale. Satellite remote sensing represents an important resource for monitoring extensive coastal zones. Previous approaches to modelling the elevation of the intertidal zone using earth observation (EO) data have been restricted to small study regions or have relied on manual image interpretation, thus limiting their ability to be applied consistently over large geographic extents. In this study, we present an automated open-source approach to generate satellite-derived elevation data for over 15,387 km 2 of intertidal terrain across the entire Australian coastline. Our approach combines global tidal modelling with a 30-year time series archive of spatially and spectrally calibrated Landsat satellite data managed within the Digital Earth Australia (DEA) platform. The resulting National Intertidal Digital Elevation Model (NIDEM) dataset provides an unprecedented three-dimensional representation of Australia's vast exposed in-tertidal zone at 25 m spatial resolution. We validate our model against LiDAR, RTK GPS and multibeam bathymetry datasets, finding that modelled elevations are highly accurate across sandy beach (± 0.41 m RMSE) and tidal flat environments (± 0.39 m RMSE). Model performance was least accurate (± 2.98 m RMSE) within rocky shores and reefs and other complex coastal environments with extreme and variable tidal regimes. We discuss key challenges associated with modelling intertidal elevation including tidal model performance and biased observations from sun-synchronous satellites, and suggest future directions to improve the accuracy and utility of continental-scale intertidal elevation modelling. Our model can be applied to tidally-influenced coastal environments globally, addressing a key gap between the availability of sub-tidal bathymetry and terrestrial elevation data.
Remote Sensing of Environment
Estuarine, Coastal and Shelf Science, 2019
The intertidal zone represents a critical transition between marine and terrestrial ecosystems, s... more The intertidal zone represents a critical transition between marine and terrestrial ecosystems, supporting a complex mosaic of highly productive and biologically diverse habitats. However, our understanding of these important coastal environments is limited by a lack of spatially consistent topographic data, which can be extremely challenging and costly to obtain at continental-scale. Satellite remote sensing represents an important resource for monitoring extensive coastal zones. Previous approaches to modelling the elevation of the intertidal zone using earth observation (EO) data have been restricted to small study regions or have relied on manual image interpretation, thus limiting their ability to be applied consistently over large geographic extents. In this study, we present an automated open-source approach to generate satellite-derived elevation data for over 15,387 km 2 of intertidal terrain across the entire Australian coastline. Our approach combines global tidal modelling with a 30-year time series archive of spatially and spectrally calibrated Landsat satellite data managed within the Digital Earth Australia (DEA) platform. The resulting National Intertidal Digital Elevation Model (NIDEM) dataset provides an unprecedented three-dimensional representation of Australia's vast exposed in-tertidal zone at 25 m spatial resolution. We validate our model against LiDAR, RTK GPS and multibeam bathymetry datasets, finding that modelled elevations are highly accurate across sandy beach (± 0.41 m RMSE) and tidal flat environments (± 0.39 m RMSE). Model performance was least accurate (± 2.98 m RMSE) within rocky shores and reefs and other complex coastal environments with extreme and variable tidal regimes. We discuss key challenges associated with modelling intertidal elevation including tidal model performance and biased observations from sun-synchronous satellites, and suggest future directions to improve the accuracy and utility of continental-scale intertidal elevation modelling. Our model can be applied to tidally-influenced coastal environments globally, addressing a key gap between the availability of sub-tidal bathymetry and terrestrial elevation data.
Ecological Indicators, 2017
In dynamic dryland regions, accounting for spatiotemporal landscape dynamics is essential to unde... more In dynamic dryland regions, accounting for spatiotemporal landscape dynamics is essential to understanding how ecological habitat networks are affected by hydroclimatic variability at regional or sub-continental scales. Here we assess how changes in the distribution and availability of surface water influence potential landscape connectivity for water-dependent organisms by combining graph theory network analysis with a Landsat-derived , seasonally continuous 25-year surface-water time-series. We focused on Australia's Murray Darling Basin (MDB), a globally significant and ecologically stressed 1 million km 2 semi-arid region recently affected by two unprecedented hydroclimatic extremes: the 1997–2010 Millennium Drought and 2010–2012 La Niña floods. We constructed potential habitat networks for two dispersal abilities using circuit theory resistance distances, and used 'habitat availability' graph theory metrics as indicators of regional-scale connectivity. We analysed 792 unique potential habitat networks containing over 6.6 million nodes, making our study one of the largest spatially explicit ecological network analyses yet conducted. Our indicators of connectivity revealed consistently positive but spatially heterogeneous relationships between flooded habitat area and landscape connectivity. Connectivity increased by over two orders of magnitude along the spectrum from severe drought to flood, associated with a transition from connectivity driven by intra-habitat or short-distance dispersal during drought to long-distance dispersal during wet conditions. Reductions in connectivity during drought were lower than expected given equivalent decreases in surface water habitat area, suggesting habitat network structure provides a degree of resistance to dry conditions. By providing insights into the processes driving connectivity during different phases along the drought-flood spectrum, our approach may assist in guiding conservation management aimed at maintaining or improving landscape connectivity within dynamic environments faced with increasing hydroclimatic variability.
Landscape connectivity is important for the long-term persistence of species inhabiting dryland f... more Landscape connectivity is important for the long-term persistence of species inhabiting dryland freshwater ecosystems, with spatiotemporal surface-water dynamics (e.g., flooding) maintaining connectivity by both creating temporary habitats and providing transient opportunities for dispersal. Improving our understanding of how landscape connectivity varies with respect to surface-water dynamics and land use is an important step to maintaining biodiversity in dynamic dryland environments. Using a newly available validated Landsat TM and ETM+ surface-water time series, we modelled landscape connectivity between dynamic surface-water habitats within Australia's 1 million km2 semi-arid Murray Darling Basin across a 25-year period (1987 to 2011). We identified key habitats that serve as well-connected ‘hubs’, or ‘stepping-stones’ that allow long-distance movements through surface-water habitat networks. We compared distributions of these habitats for short- and long-distance dispersal species during dry, average and wet seasons, and across land-use types. The distribution of stepping-stones and hubs varied both spatially and temporally, with temporal changes driven by drought and flooding dynamics. Conservation areas and natural environments contained higher than expected proportions of both stepping-stones and hubs throughout the time series; however, highly modified agricultural landscapes increased in importance during wet seasons. Irrigated landscapes contained particularly high proportions of well-connected hubs for long-distance dispersers, but remained relatively disconnected for less vagile organisms. The habitats identified by our study may serve as ideal high-priority targets for land-use specific management aimed at maintaining or improving dispersal between surface-water habitats, potentially providing benefits to biodiversity beyond the immediate site scale. Our results also highlight the importance of accounting for the influence of spatial and temporal surface-water dynamics when studying landscape connectivity within highly variable dryland environments.
Context: Landscape-scale research quantifying ecological connectivity is required to maintain the... more Context: Landscape-scale research quantifying ecological connectivity is required to maintain the viability of populations in dynamic environments increasingly impacted by anthropogenic modification and environmental change.
Objective: To evaluate how surface water network structure, landscape resistance to movement, and flooding affect the connectivity of amphibian habitats within the Murray–Darling Basin (MDB), a highly modified but ecologically significant region of south-eastern Australia.
Methods: We evaluated potential connectivity network graphs based on circuit theory, Euclidean and least-cost path distances for two amphibian species with different dispersal abilities, and used graph theory metrics to compare regional- and patch-scale connectivity across a range of flooding scenarios.
Results: Circuit theory graphs were more connected than Euclidean and least-cost equivalents in floodplain environments, and less connected in highly modified or semi-arid regions. Habitat networks were highly fragmented for both species, with flooding playing a crucial role in facilitating landscape-scale connectivity. Both formally and informally protected habitats were more likely to form important connectivity “hubs” or “stepping stones” compared to non-protected habitats, and increased in importance with flooding.
Conclusions: Surface water network structure and the quality of the intervening landscape matrix combine to affect the connectivity of MDB amphibian habitats in ways which vary spatially and in response to flooding. Our findings highlight the importance of utilising organism-relevant connectivity models which incorporate landscape resistance to movement, and accounting for dynamic landscape-scale processes such as flooding when quantifying connectivity to inform the conservation of dynamic and highly modified environments.
Conference Presentations by Robbi Bishop-Taylor
Landscape-scale research quantifying ecological connectivity is urgently required to maintain the... more Landscape-scale research quantifying ecological connectivity is urgently required to maintain the viability of populations in dynamic environments impacted by anthropogenic modification and environmental change. We evaluated how surface water network structure, landscape resistance-to-movement, and flooding affect amphibian habitat connectivity within the Murray-Darling Basin, a highly modified but ecologically significant region of south-eastern Australia. We created circuit theory, Euclidean and least-cost potential connectivity networks for two amphibians with different dispersal abilities, and used graph theory metrics to compare regional- and patch-scale connectivity across a range of flooding scenarios. Circuit theory networks were more connected than Euclidean and least-cost equivalents in floodplain environments, and less connected in highly modified or semi-arid regions. Networks were highly fragmented for both species, with flooding critical for facilitating landscape-scale connectivity. Both formally and informally protected habitats were more likely to form important connectivity "hubs" or "stepping-stones" compared to non-protected habitats, and increased in importance with flooding. In the Murray-Darling, habitat network structure and the landscape matrix affect connectivity in ways which vary spatially and in response to flooding. Our findings highlight the importance of utilising organism-relevant connectivity models which incorporate landscape resistance-to-movement, and incorporating dynamic landscape-scale processes such as flooding when quantifying connectivity to inform conservation.
Geological Society of Australia, 2014 Australian Earth Sciences Convention (AESC), Sustainable Australia. 22nd Australian Geological Convention, Newcastle, New South Wales. July 7-10
While the interdisciplinary field of geoarcheology now often involves petrological surveys at arc... more While the interdisciplinary field of geoarcheology now often involves petrological surveys at archeological sites, the Kazanlak Geoscience Project aimed to go back to the geomorphology-based beginnings of the field to demonstrate how a simple soil survey could be beneficial to an archeological project. During the 2011 autumn season of the Tundzha Regional Archaeology Project (TRAP), a small geoscience team conducted such a soil survey across the Kazanlak valley in central Bulgaria. Sample sites were randomly selected using stratified systematic random sampling (SSRS), and 155 soil samples were collected. The soil was tested for organic matter content, carbonate content, texture and coarse fraction, with the results analysed and interpolated in a GIS to determine spatial patterns in each of these soil properties within the study area. The data were then used in combination with topographic and land cover datasets to produce a quantitative model of soil erosion potential for the region, which predicted erosion rates of up to 895 t/ha/yr or 70 mm/yr. These findings have various potential applications, such as past landscape reconstructions or in determining spatial relationships between soil properties, landscape stability and surface distribution of archeological artefacts.
19th Annual Meeting of the European Association of Archaeologists (4-8 September 2013, Pilsen, Czech Republic)
Site catchment analysis has a long history in archaeological studies. It has been used to explore... more Site catchment analysis has a long history in archaeological studies. It has been used to explore a wide range of topics from changing land use patterns to socio-political organization. In this paper we discuss the results of site catchment analysis applied to the Late Bronze Age, Iron Age, and Roman eras in the Kazanlak Valley, Bulgaria, especially the evolving relationship between past inhabitants and their environment. Combining geoarchaeological data, geographic modelling, and multivariate cluster analysis, this study develops a quantitative potential arable productivity model for the cultivation of wheat and barley. We contextualise this model with settlement data produced through systematic surface survey conducted by the Tundzha Regional Archaeological Project (TRAP). Arable productivity proved to be a significant factor controlling the location of settlements within the study area during all periods except for the Early Iron Age. Multivariate cluster analysis produced three distinct productivity-based site classifications, and successfully delineated strategic site locations from those chosen based on agricultural potential. This study demonstrates how catchment analysis can reveal the factors determining human habitation in later prehistory. This arable productivity model also provides one of the inputs for site catchment analysis.
19th Annual Meeting of the European Association of Archaeologists (4-8 September 2013, Pilsen, Czech Republic)
During surface survey, the Tundzha Regional Archaeological Project (TRAP) identified a network of... more During surface survey, the Tundzha Regional Archaeological Project (TRAP) identified a network of surface concentrations across the Kazanlak valley. Subsequent trial excavations revealed that the sites associated with these concentrations represented short term and shifting habitations, a pattern observed elsewhere in Bulgaria during later prehistory. Scholars have interpreted the frequency of single-phase sites and the absence of structures built from durable materials as signs of increasing mobility in previously sedentary populations. The settlements explored by TRAP often gravitated towards particular topographic areas, indicating that habitation, while shifting, does display patterns over time. In order to understand these patterns and their relationships to subsistence strategies, this paper uses data from surface survey, soil geochemistry, and ethnography to model the footprints of various agro-pastoral regimes, from pure cereal agriculture to pure stockbreeding. We calculate the extent of land required by various strategies to support settlements of the size revealed by survey and subsequent excavation, in light of likely productivity, as calculated from a dynamic arable productivity model. We conclude by assessing which subsistence models best correspond to the observed settlement patterns during the first millennium BC.
Thesis Chapters by Robbi Bishop-Taylor
The Upper Tundzha valley, Bulgaria is one of most significant yet least systematically... more The Upper Tundzha valley, Bulgaria is one of most significant yet least systematically studied archaeological landscapes in south-eastern Europe. This study developed a diachronic spatial approach for the analysis of Prehistoric, Bronze Age, Iron Age and Roman settlement data recently made available by the
Tundzha Regional Archaeological Project (TRAP). Using techniques developed for landscape archaeology, this research identified temporally variable influences of environmental and cultural factors on human activity. These results contribute to current understanding of regional changes in settlement patterns, subsistence
strategies, strategic considerations and cultural factors, providing an important starting point for further analysis of developing social complexity throughout the region’s 8000 year history.
Reports by Robbi Bishop-Taylor
Environmental flows will soon be passed through Cowarra Dam in the form of a transpar... more Environmental flows will soon be passed through Cowarra Dam in the form of a transparent environmental flow regime. Larger discharges are clearly relevant to the flushing of streams like Cowarra-dam Creek that have been impacted by sedimentation. Accordingly, the objective of the present investigation was: To develop an initial understanding of the appropriate scale (magnitude and duration) of a discharge that is likely to flush deposited silts and clays from Cowarra-dam Creek. An additional focus was the identification of a discharge that will flush away excessive accumulations of leaf litterand improve important water quality features, notably dissolved oxygen(DO).The effectiveness of a single discharge event was investigated using before-and-after replicated measurements of the following variables at four downstream sites: 1) level of the underlying clay bed, 2) the abundance of leaf litter,and 3) surface and 4) near-bed DO concentrations. The release of ambient-temperature water was made over a one-hour period on 4th December 2008. A total volume of 10.56 ML was discharged with a peak flow rate of 267 ML/d,which persisted for the majority of the release time. The rectangular shape of the resulting hydrograph was highly unnatural, yet in terms of release volume and peak discharge rate, it was established that it was well within what would be expected under natural conditions.The discharge removed the majority of the excessive leaf litter accumulation from the centre portion of the creek and DO conditions improved dramatically. Near-bed DO conditions improved least and some deterioration had occurred 12-days after the discharge. It appears likely that the underlying clay bed has a high sediment oxygen demand (SOD),a result of either a high organic content or an abundant supply of reduced ‘chemical species’. If the deposited clays/silts have a persistent high SOD, it follows that they have an environmental liability additional to the habitat loss impact caused by the sedimentation. This possibility should be investigated by continued monitoring of DO,and if needs be, in situ measurements of SOD.The discharge removed substantial amounts of the underlying clay base in only the most upstream site. Unfortunately,further downstream deposition occurred. Accordingly, the use of larger discharges or the mechanical removal of the sediment is indicated, if this can be done without damaging the riparian zone of the creek. There was no geomorphic or environmental information gathered which indicated that experimentation with larger flushing discharges should not proceed.An examination of approaches to determine the shape of hydrographs for transparent environmental flows (TEFs) along the NSW coast indicated that the use of rainfall data is impractical and unreliable. The primary guide should be stream gauging in a representative catchment. Such a catchment (Sapling Creek) occurs within two kilometres of Cowarra Dam and it was recommended that the possibility of installing a gauging weir at an identified point be assessed.It was further recommended that Clarence Valley Council (who built Shannon Creek Dam) be interacted with on issues concerning TEFs so to be in a better position when developing a state-of-the-art system for Cowarra Dam.
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Papers by Robbi Bishop-Taylor
Objective: To evaluate how surface water network structure, landscape resistance to movement, and flooding affect the connectivity of amphibian habitats within the Murray–Darling Basin (MDB), a highly modified but ecologically significant region of south-eastern Australia.
Methods: We evaluated potential connectivity network graphs based on circuit theory, Euclidean and least-cost path distances for two amphibian species with different dispersal abilities, and used graph theory metrics to compare regional- and patch-scale connectivity across a range of flooding scenarios.
Results: Circuit theory graphs were more connected than Euclidean and least-cost equivalents in floodplain environments, and less connected in highly modified or semi-arid regions. Habitat networks were highly fragmented for both species, with flooding playing a crucial role in facilitating landscape-scale connectivity. Both formally and informally protected habitats were more likely to form important connectivity “hubs” or “stepping stones” compared to non-protected habitats, and increased in importance with flooding.
Conclusions: Surface water network structure and the quality of the intervening landscape matrix combine to affect the connectivity of MDB amphibian habitats in ways which vary spatially and in response to flooding. Our findings highlight the importance of utilising organism-relevant connectivity models which incorporate landscape resistance to movement, and accounting for dynamic landscape-scale processes such as flooding when quantifying connectivity to inform the conservation of dynamic and highly modified environments.
Conference Presentations by Robbi Bishop-Taylor
Thesis Chapters by Robbi Bishop-Taylor
Tundzha Regional Archaeological Project (TRAP). Using techniques developed for landscape archaeology, this research identified temporally variable influences of environmental and cultural factors on human activity. These results contribute to current understanding of regional changes in settlement patterns, subsistence
strategies, strategic considerations and cultural factors, providing an important starting point for further analysis of developing social complexity throughout the region’s 8000 year history.
Reports by Robbi Bishop-Taylor
Objective: To evaluate how surface water network structure, landscape resistance to movement, and flooding affect the connectivity of amphibian habitats within the Murray–Darling Basin (MDB), a highly modified but ecologically significant region of south-eastern Australia.
Methods: We evaluated potential connectivity network graphs based on circuit theory, Euclidean and least-cost path distances for two amphibian species with different dispersal abilities, and used graph theory metrics to compare regional- and patch-scale connectivity across a range of flooding scenarios.
Results: Circuit theory graphs were more connected than Euclidean and least-cost equivalents in floodplain environments, and less connected in highly modified or semi-arid regions. Habitat networks were highly fragmented for both species, with flooding playing a crucial role in facilitating landscape-scale connectivity. Both formally and informally protected habitats were more likely to form important connectivity “hubs” or “stepping stones” compared to non-protected habitats, and increased in importance with flooding.
Conclusions: Surface water network structure and the quality of the intervening landscape matrix combine to affect the connectivity of MDB amphibian habitats in ways which vary spatially and in response to flooding. Our findings highlight the importance of utilising organism-relevant connectivity models which incorporate landscape resistance to movement, and accounting for dynamic landscape-scale processes such as flooding when quantifying connectivity to inform the conservation of dynamic and highly modified environments.
Tundzha Regional Archaeological Project (TRAP). Using techniques developed for landscape archaeology, this research identified temporally variable influences of environmental and cultural factors on human activity. These results contribute to current understanding of regional changes in settlement patterns, subsistence
strategies, strategic considerations and cultural factors, providing an important starting point for further analysis of developing social complexity throughout the region’s 8000 year history.