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Note that this Record has now been published as Record 2014/050, GeoCat number 78802
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Legacy product - no abstract available
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The service includes an outline of the Australian shoreline. The information was derived from the Geodata 3 Topographic 250K 2007 data, with a nominal scale of 1:250,000. It is a cached service with a Web Mercator Projection.
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The Fitzoy Estuary is one of several macrotidal estuaries in tropical northern Australia that face ecological change due to agricultural activities in their catchments. The biochemical functioning of such macrotidal estuaries is not well understood in Australia, and there is a pressing need to identify sediment, nutrient and agrochemical pathways, sinks and accumulation rates in these extremely dynamic environments. This is particularly the case in coastal northern Queensland because the impact of water quality changes in rivers resulting from vegetation clearing, changes in land-use and modern agricultural practices are the single greatest threat to the Great Barrier Reef Marine Park. This report includes: 1 Aims and Research questions 2 Study Area 3 Climate and Hydrology 4 Geology 5 Vegetation and land use 6 Methods 7 Sampling strategy 8 Water column observations and samples 9 Bottom sediment properties 10 Core and bottle incubations 11 Data analysis 12 Results 13 Discussion 14 The roll of Keppel Bay in accumulating and redirecting sediment and nutrients from the catchment 15 Sediment biogeochemistry 16 Links between primary production, biogeochemistry and sediment dynamics: A preliminary zonation for Keppel Bay 17 Conclusions
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The East Australian Current (EAC) onshore encroachment drives coastal upwelling and shelf circulations, changes slope-shelf bio-physical dynamics, and consequently exerts significant influence on coastal marine ecosystem along the south-eastern Australian margin. The EAC is a highly dynamic eddy-current system which exhibits high-frequency intrinsic fluctuations and eddy shedding. As a result, low-frequency variability in the EAC is usually overshadowed and rarely detectable. For decades, despite many efforts into the ocean current observations, the seasonality of EAC’s shoreward intrusion remains highly disputable. In this study, for the first time we use a long-term (26 years) remotely sensed AVHRR Sea Surface Temperature (SST) dataset spanning 1992-2018 to map the EAC off the coast of northern New South Wales (NSW), between 28°S - 32.5°S. A Topographic Position Index (TPI) image processing technique was applied to conduct the quantitative mapping. The mapping products have enabled direct measurement (area and distance) of the EAC’s shoreward intrusion. Subsequent spatial and temporal analyses have shown that the EAC move closer to the coast in austral summer and autumn than in austral winter, with the mean distance-to-coast ~6 km shorter and occupying the shelf area ~12% larger. This provides quantitative and direct evidence of the seasonality of the EAC’s shoreward intrusion. Such seasonal migration pattern of the EAC thus provides new insights into the seasonal upwelling and shelf circulations previously observed in this region. As a result, we were able to confirm that the EAC is a driving force of the seasonal ocean dynamics for the northern NSW coast.
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Beach ridges at Keppel Bay, central Queensland, Australia, preserve a record of sediment accumulation from the historical period back to middle Holocene times. The ridges comprise fine, well-sorted, feldspar-rich quartz sand that was eroded from the Fitzroy River catchment, deposited in Keppel Bay during floods of the Fitzroy River, and reworked onshore into beach and foredune deposits by the prevailing currents, waves and wind. These floods have an average recurrence interval of at least 7 yr and are induced by the passage of cyclones onshore into the large Fitzroy catchment. The youngest series of beach ridges sit sub-parallel to the modern beach and comprise six accretional units, each unit formed by a set of ridges and delineated by prominent swales. Optically stimulated luminescence (OSL) ages of beach ridges in these units indicate they were deposited in periods of rapid progradation approximately 1500, 1000, 450 and 230 yr BP, when there was an enhanced supply of sediment to the beach from the Fitzroy River via Keppel Bay. Estimates of the mass of sediment stored in the beach-ridge strandplain show that it represents a significant sediment store, potentially trapping the equivalent of 79% of the estimated long-term (100 yr) average annual bedload of the Fitzroy River that is deposited in Keppel Bay. There has been a reduction in the rate of sediment accumulation in the strandplain since around 1000 yr BP, which is consistent with other coastal records in eastern Australia of a relatively wetter phase of climate in the late Holocene compared to the present. The youngest beach ridges (OSL ages < 100 yr BP) are tall relict foredunes that reflect a low rate of sediment accumulation. These ridges have a distinctive trace-element composition produced by a greater contribution from catchment areas with basaltic soils. The change in catchment provenance has likely been a consequence of erosion that followed clearing of native vegetation in these areas. Our findings demonstrate the important insights that beach-ridge deposits proximal to a river sediment source can provide into processes of sediment accumulation and the response to variations in climate in tropical coastal sedimentary systems.
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We examine surface sediment and water column total nutrient and chlorophyll a concentrations for 12 estuaries with average water depths <4 m, and calculated sediment loads ranging from 0.2 to 10.8 kg m-2 year-1. Sediment total nitrogen, phosphorus and organic carbon concentrations vary inversely with sediment loads due to: (i) the influx of more mineral-rich sediment into the estuaries; and (ii) increasing sediment sulfidation. Sediment total organic carbon (TOC) : total sulfur (TS) and TS : Fe(II) ratios correlated to sediment loads because enhanced sedimentation increases burial, hence the importance of sulfate reduction in organic matter degradation. Curvilinear relationships were found between a weathering index and organic matter 13C in sediment, and sediment load. The rising phase of the curve (increasing weathering, lighter isotopic values) at low to intermediate loads relates to soil erosion, whereas regolith or bedrock erosion probably explains the declining phase of the curve (decreasing weathering, heavier isotopic values) at higher sediment loads. The pattern of change for water column total nutrients (nitrogen and phosphorus) with sediment loads is similar to that of the weathering index. Most water quality problems occur in association with soil erosion, and at sediment loads that are intermediate for the estuaries studied. Limited evidence is presented that flushing can moderate the impact of sediment loads upon the estuaries.
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Approximately 85% of Australia's population and much of its critical infrastructure is focused around the coastal zone. Continued migration to the coast and increasing coastal development creates challenges for coastal management and planning. It is anticipated that climate change will exacerbate these challenges in the coming decades through rising sea levels and more intense and frequent storms. These impacts will lead to increased risk of inundation, storm surge and coastal erosion which will damage beaches, property and infrastructure along susceptible shorelines and low-lying coastal areas and adversely affect a significant number of Australian coastal communities. The Australian Government's Framework for a National Cooperative Approach to Integrated Coastal Zone Management identified a need to 'build a national picture of coastal zone areas that are particularly vulnerable to climate change impacts to better understand the risks and interactions with other stressors in the coastal zone'. Decision-makers at all government levels need access to information to assist development and planning decisions and to identify valuable human and natural assets that require protection. Further to this aim, Geoscience Australia (GA) is assisting the Department of Climate Change to develop a 'first pass' National Coastal Vulnerability Assessment. This is providing fundamental information that will support decision-makers by identifying areas in Australia's coastal zone where potential impacts may be rated as high, medium and low. Potential climate change impacts have been assessed for cyclonic winds and coastal inundation from a combination of sea-level rise and storm surge scenarios.
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Some of the most visible consequences arising from climate change are sea level rise and more intense and frequent storms. On the open coast and low lying estuarine waterways these impacts will lead to the increased risks of inundation, storm surge and coastal erosion that can damage beaches, property and infrastructure and impact on a significant number of people. Understanding the potential risk of these coastal hazards is critical for coastal zone management and the formulation of adaptation responses, while early action is likely to be the most cost effective approach to managing the risk. Geoscience Australia (GA) is assisting the Australian Government's Department of Climate Change to develop a 'first pass' National Coastal Vulnerability Assessment. GA and the University of Tasmania (UTas) are developing fundamental spatial datasets and GIS modelling tools to identify which land areas of the Australian coast are likely to be physically sensitive to the effects of sea level rise, storms and storm surge. Of special interest is to identify sensitive areas where there is significant property and infrastructure that will be the focus of a more detailed study in a second pass assessment. A new national shoreline geomorphic and stability map or Smartline, developed for the project by UTas, is a key new spatial dataset. The Smartline is an interactive, nationally-consistent coastal GIS map in the form of a segmented line. Each line segment identifies distinct coastal landform types using multiple attribute fields to describe important aspects of the geology, geomorphology and topography of the coast. These data enable an assessment of the stability of the coast and its sensitivity to the potential impacts of shoreline erosion (soft coast) and inundation (low-lying coast), providing a useful indicative coastal risk assessment.
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In this paper a new benchmark for tsunami model validation is pro- posed. The benchmark is based upon the 2004 Indian Ocean tsunami, which provides a uniquely large amount of observational data for model comparison. Unlike the small number of existing benchmarks, the pro- posed test validates all three stages of tsunami evolution - generation, propagation and inundation. Specifically we use geodetic measurements of the Sumatra{Andaman earthquake to validate the tsunami source, al- timetry data from the jason satellite to test open ocean propagation, eye-witness accounts to assess near shore propagation and a detailed inundation survey of Patong Bay, Thailand to compare model and observed inundation. Furthermore we utilise this benchmark to further validate the hydrodynamic modelling tool anuga which is used to simulate the tsunami inundation. Important buildings and other structures were incorporated into the underlying computational mesh and shown to have a large inuence of inundation extent. Sensitivity analysis also showed that the model predictions are comparatively insensitive to large changes in friction and small perturbations in wave weight at the 100 m depth contour.