Knowledge of the nature of buildings within business precincts is fundamental to a broad range of decision making processes, including planning, emergency management and the mitigation of the impact of natural hazards. To support these activities, Geoscience Australia has developed a building information system called the National Exposure Information System (NEXIS) which provides information on buildings across Australia. Most of the building level information in NEXIS is statistically derived, but efforts are being made to include more detailed information on the nature of individual buildings, particularly in business districts. This is being achieved in Sydney through field survey work.

This Geoscience Australia Record documents the scientific analysis undertaken, and results obtained from geodetic monitoring during the Camden Environmental Monitoring Project (CEMP); a collaborative project undertaken with the New South Wales Department of Planning, Industry and Environment. The aim of the CEMP was to determine the environmental impacts, if any, of active coal seam gas extraction projects in New South Wales. Geodetic monitoring, using satellite radar interferometry (InSAR) and Global Positioning System (GPS) measurements, was used to specifically assess if subsidence (downward vertical land movement) is occurring at the Camden Gas Project; at the time the State’s only actively producing coal seam gas project. To address this question, Geoscience Australia undertook a comprehensive InSAR analysis using data sets from three orbiting radar satellites (ALOS, Envisat and Radarsat-2) covering two periods of time (2006 to 2010, and 2015 to 2019). The outputs of this InSAR analysis are vertical and horizontal ground surface displacement and velocity map products, together with a quantification of the uncertainty of these measurements. Furthermore, a new network of 20 ground geodetic monitoring sites was established in May and June 2016 for the purpose of validating measurements made using InSAR. GPS data was collected at these monitoring sites between July 2016 and June 2019 and processed to obtain 3-dimensional ground surface displacement and velocity measurements. From the analysis of independent InSAR and GPS data sets undertaken during the CEMP, we conclude that no measurable subsidence (i.e. a land movement velocity not greater than 10 mm/yr) has occurred as a result of coal seam gas production in the Camden Gas Project during the time periods of monitoring. However, decimetre-scale horizontal and vertical surface movements have occurred in the Southern Coalfields at the locations of subsurface longwall coal mines. Comparison of the measurements made by InSAR and GPS across the 20-site geodetic monitoring network shows that the two independent geodetic techniques agree within 10 millimetres, even when decimetre-scale movement is occurring. This demonstrates the potential for utilising InSAR for accurate remote monitoring of ground surface movements (including subsidence) at large scales and in the absence of sufficient ground geodetic monitoring infrastructure. The conclusions drawn and the measurements made in this work are specific to the area covered by the CEMP geodetic monitoring project, and are therefore not applicable to other resource extraction activities in other areas because of operational and geological differences from site to site. However, the methods described herein would be applicable to monitoring other resource extraction activities.

<div>The Georges River (Sydney Region) 5m Digital Elevation Model (DEM) is generated from all relevant data available on the Elvis - Elevation and Depth - Foundation Spatial Data (Elvis) platform with a resolution of 5 Metres or higher. Source datasets with a resolution higher than 5m have been resampled to 5m.</div><div>This elevation model is generated from a total of 989 datasets sourced from multiple providers including State and Territory Governments. The capture dates for input data range from 2011/02/26 - 2021/06/05. See Table 1 below for further information. The area covers the land mass of the Georges River (Sydney Region) drainage basin as defined by the Bureau of Meteorology Geofabric.</div>

<div>The city of Sydney, Australia has been growing rapidly over the last decades, with rapid development of residential and transportation infrastructure. Land subsidence associated with the urban development can lead to serious issues which should be thoroughly understood and carefully managed. Hence&nbsp;this study developed an enhanced multi-polarisation time-series InSAR (Pol-TS-InSAR) processing framework to address this challenging application.&nbsp;This is done by integrating the information from different polarimetric channels with different weighting during the TS-InSAR analysis. Ninety&nbsp;dual polarization Sentinel-1 images&nbsp;acquired from&nbsp;2019 to 2022 are analysed using the developed&nbsp;Pol-TS-InSAR to map the land subsidence in Sydney with the assistance of the GPS measurements. Improvement of measurement points density from Pol-TS-InSAR is observed compared to the single polarimetric TS-InSAR counterpart for all land use types (ranging between 21% and 99%). The comparison between the Pol-TS-InSAR measurements and GPS measurements shows an&nbsp;absolute mean difference and RMS difference of 0.7 mm/yr and 0.9 mm/yr, respectively, in line-of-sight (LoS) direction. The ground subsidence results obtained have been investigated.&nbsp;It is found that the main subsidence factors in Sydney are related to groundwater extraction, mining activities, underground tunnel construction and landfill, which the latter two factors are less aware previously. In additional to these factors, land subsidence related to high-rise building construction has also been observed, even though the impact seems to be less significant than other factors. <b>Citation:</b> Alex Hay-Man Ng, Ziyue Liu, Zheyuan Du, Hengwei Huang, Hua Wang, Linlin Ge, A novel framework for combining polarimetric Sentinel-1 InSAR time series in subsidence monitoring - A case study of Sydney,<i>Remote Sensing of Environment</i>, Volume 295, <b>2023</b>, 113694, ISSN 0034-4257. https://doi.org/10.1016/j.rse.2023.113694.

This report, completed as part of Geoscience Australia’s Exploring for the Future Program National Groundwater Systems (NGS) Project, presents results of the second iteration of 3D geological and hydrogeological surfaces across eastern Australian basins. The NGS project is part of the Exploring for the Future (EFTF) program—an eight-year, $225 million Australian Government funded geoscience data and precompetitive information acquisition program. The program seeks to inform decision-making by government, community, and industry on the sustainable development of Australia's mineral, energy, and groundwater resources, including those to support the effective long-term management of GAB water resources. This work builds on the first iteration completed as part of the Great Artesian Basin Groundwater project. The datasets incorporate infills of data and knowledge gaps in the Great Artesian Basin (GAB), Lake Eyre Basin (LEB), Upper Darling Floodplain (UDF) and existing data in additional basins in eastern Australia. The study area extends from the offshore Gulf of Carpentaria in the north to the offshore Bight, Otway, and Gippsland basins in the South and from the western edge of the GAB in the west to the eastern Australian coastline to the east. The revisions are an update to the surface extents and thicknesses for 18 region-wide hydrogeological units produced by Vizy & Rollet, 2022. The second iteration of the 3D model surfaces further unifies geology across borders and provides the basis for a consistent hydrogeological framework at a basin-wide, and towards a national-wide, scale. The stratigraphic nomenclature used follows geological unit subdivisions applied: (1) in the Surat Cumulative Management Area (OGIA - Office of Groundwater Impact Assessment, 2019) to correlate time equivalent regional hydrogeological units in the GAB and other Jurassic and Cretaceous time equivalent basins in the study area and (2) in the LEB to correlate Cenozoic time equivalents in the study area. Triassic to Permian and older basins distribution and thicknesses are provided without any geological and hydrogeological unit sub-division. Such work helps to (1) reconcile legacy and contemporary regional studies under a common stratigraphic framework, (2) support the effective management of groundwater resources, and (3) provide a regional geological context for integrated resource assessments. The 18 hydrogeological units were constructed using legacy borehole data, 2D seismic and airborne electromagnetic (AEM) data that were compiled for the first iteration of the geological and hydrogeological surfaces under the GAB groundwater project (Vizy & Rollet, 2022a) with the addition of: • New data collected and QC’d from boreholes (including petroleum, CSG [Coal Seam Gas], stratigraphic, mineral and water boreholes) across Australia (Vizy & Rollet, 2023a) since the first iteration, including revised stratigraphic correlations filling data and knowledge gaps in the GAB, LEB, UDF region (Norton & Rollet, 2023) with revised palynological constraints (Hannaford & Rollet 2023), • Additional AEM interpretation since the first iteration in the GAB, particularly in the northern Surat (McPherson et al., 2022b), as well as in the LEB (Evans et al., in prep), in the southern Eromanga Basin (Wong et al., 2023) and in the UDF region (McPherson et al., 2022c), and • Additional 2D seismic interpretation in the Gulf of Carpentaria (Vizy & Rollet, 2023b) and in the western and central Eromanga Basin (Szczepaniak et al., 2023). These datasets were then analysed and interpreted in a common 3D domain using a consistent chronostratigraphic framework tied to the geological timescale of 2020, as defined by Hannaford et al. (2022). Confidence maps were also produced to highlight areas that need further investigation due to data gaps, in areas where better seismic depth conversion or improved well formation picks are required. New interpretations from the second iteration of the 18 surfaces include (1) new consistent and regionally continuous surfaces of Cenozoic down to Permian and older sediments beyond the extent of the GAB across eastern Australia, (2) revised extents and thicknesses of Jurassic and Cretaceous units in the GAB, including those based on distributed thickness, (3) revised extents and thicknesses of Cenozoic LEB units constrained by the underlying GAB 3D model surfaces geometry. These data constraints were not used in the model surfaces generated for the LEB detailed inventory (Evans et al., 2023), and (4) refinements of surfaces due to additional seismic and AEM interpretation used to infill data and knowledge gaps. Significant revisions include: • The use of additional seismic data to better constrain the base of the Poolowanna-Evergreen formations and equivalents and the top of Cadna-owie Formation and equivalents in the western and central Eromanga Basin, and the extent and thicknesses of the GAB units and Cenozoic Karumba Basin in the Gulf of Carpentaria, • The use of AEM interpretations to refine the geometry of outcropping units in the northern Surat Basin and the basement surface underneath the UDF region, and • A continuous 3D geological surface of base Cenozoic sediments across eastern Australia including additional constraints for the Lake Eyre Basin (borehole stratigraphy review), Murray Basin (AEM interpretation) and Karumba Basin (seismic interpretation). These revisions to the 18 geological and hydrogeological surfaces will help improve our understanding on the 3D spatial distribution of aquifers and aquitards across eastern Australia, from the groundwater recharge areas to the deep confined aquifers. These data compilations and information brought to a common national standard help improve hydrogeological conceptualisation of groundwater systems across multiple jurisdictions to assist water managers to support responsible groundwater management and secure groundwater into the future. These 3D geological and hydrogeological modelled surfaces also provide a tool for consistent data integration from multiple datasets. These modelled surfaces bring together variable data quality and coverage from different databases across state and territory jurisdictions. Data integration at various scale is important to assess potential impact of different water users and climate change. The 3D modelled surfaces can be used as a consistent framework to map current groundwater knowledge at a national scale and help highlight critical groundwater areas for long-term monitoring of potential impacts on local communities and Groundwater Dependant Ecosystems. The distribution and confidence on data points used in the current iteration of the modelled surfaces highlight where data poor areas may need further data acquisition or additional interpretation to increase confidence in the aquifers and aquitards geometry. The second iteration of surfaces highlights where further improvements can be made, notably for areas in the offshore Gulf of Carpentaria with further seismic interpretation to better constrain the base of the Aptian marine incursion (to better constrain the shape and offshore extent of the main aquifers). Inclusion of more recent studies in the offshore southern and eastern margins of Australia will improve the resolution and confidence of the surfaces, up to the edge of the Australian continental shelf. Revision of the borehole stratigraphy will need to continue where more recent data and understanding exist to improve confidence in the aquifer and aquitard geometry and provide better constraints for AEM and seismic interpretation, such as in the onshore Carpentaria, Clarence-Moreton, Sydney, Murray-Darling basins. Similarly adding new seismic and AEM interpretation recently acquired and reprocessed, such as in the eastern Eromanga Basin over the Galilee Basin, would improve confidence in the surfaces in this area. Also, additional age constraints in formations that span large periods of time would help provide greater confidence to formation sub-divisions that are time equivalent to known geological units that correlate to major aquifers and aquitards in adjacent basins, such as within the Late Jurassic‒Early Cretaceous in the Eromanga and Carpentaria basins. Finally, incorporating major faults and structures would provide greater definition of the geological and hydrogeological surfaces to inform with greater confidence fluid flow pathways in the study area. This report is associated with a data package including (Appendix A – Supplementary material): • Nineteen geological and hydrogeological surfaces from the Base Permo-Carboniferous, Top Permian, Base Jurassic, Base Cenozoic to the surface (Table 1.1), • Twenty-one geological and hydrogeological unit thickness maps from the top crystalline basement to the surface (Figure 3.1 to Figure 3.21), • The formation picks and constraining data points (i.e., from boreholes, seismic, AEM and outcrops) compiled and used for gridding each surface (Table 2.7). Detailed explanation of methodology and processing is described in the associated report (Vizy & Rollet, 2023).

High-precision radiometric dating using Chemical Abrasion-Isotope Dilution Thermal Ionisation Mass Spectrometry (CA-IDTIMS) has allowed the recalibration of the numerical ages of Permian and Triassic spore-pollen palynozones in Australia. These changes have been significant, with some zonal boundaries in the Permian shifting by as much as six million years, and some in the Triassic by more than twice that. Most of the samples analysed came from eastern Australian coal basins (Sydney, Gunnedah, Bowen, Galilee) where abundant volcanic ash beds occur within the coal-bearing successions. The recalibrations of these widely used palynozones have implications for the dating of geological events outside the basins from where samples were obtained. Our revised dates for the Permian palynozones can now be applied to all Permian basins across Australia, including the Perth, Carnarvon, Canning and Bonaparte basins (along the western and northern continental margins), the Cooper and Galilee basins (in central Australia), and the Bowen, Gunnedah and Sydney basins (in eastern Australia). Revised regional stratigraphic frameworks are presented here for some of these basins. The impact of an improved calibration of biostratigraphic zones to the numerical timescale is broad and far-reaching. For example, the more accurate stratigraphic ages are the more closely burial history modelling will reflect the basin history, thereby providing control on the timing of kerogen maturation, and hydrocarbon expulsion and migration. These improvements can in turn be expected to translate in to improved exploration outcomes. We have initially focused on the Permian and provide preliminary results for the Triassic, but intend to expand recalibrations to include Jurassic, Cretaceous and Paleozoic successions beyond the Permian. Preliminary data indicates that significant changes to these calibrations are also likely.