<div>The Abbot Point to Hydrographers Passage bathymetry survey was acquired for the Australian Hydrographic Office (AHO) onboard the RV Escape during the period 6 Oct 2020 – 16 Mar 2021. This was a contracted survey conducted for the Australian Hydrographic Office by iXblue Pty Ltd as part of the Hydroscheme Industry Partnership Program. The survey area encompases a section of Two-Way Route from Abbot Point through Hydrographers Passage QLD. Bathymetry data was acquired using a Kongsberg EM 2040, and processed using QPS QINSy. The dataset was then exported as a 30m resolution, 32 bit floating point GeoTIFF grid of the survey area.</div><div>This dataset is not to be used for navigational purposes.</div>

A mini-poster on GA's capability in tsunami hazard modelling.

A new methodology is proposed to estimate storm demand and dune recession by clustered and non-clustered events, to determine if the morphological response to storm clusters results in greater beach erosion than that from individual storms that have the same average recurrence interval (ARI) or return period. The method is tested using a numerical morphodynamic model that combines both cross-shore and longshore beach profile evolution processes, forced by a 2D wave transformation model, and is applied as an example within a 20 km long coastal cell at an erosion hotspot at Old Bar, NSW mid-north coast, Australia. Wave and water level data hindcast in previous modelling (Davies et al., 2017) were used to provide two thousand different synthetic wave and tide records of 100 years duration for input to a nested nearshore 2D SWAN model that provides wave conditions at the 12 m depth contour. An open-source shoreline evolution model was used with these wave conditions to model cross-shore and longshore beach profile evolution, and was calibrated and verified against long-term dune recession observations. After a 50 year model spin up, 50 years of storm demand (change in sub-aerial beach volume) and dune toe position were simulated and ranked to form natural estimators for the 50, 25, 16, 12.5 and 10 year return period of individual events, together with confidence limits. The storm demand analysis was then repeated to find the return period of clustered and non-clustered morphological events. Morphological clusters are defined here by considering the response of the beach, rather than the forcing, with a sensitivity analysis of the influence of different recovery thresholds between storms also investigated. The new analysis approach provides storm demand versus return period curves for the combined population of clustered and non-clustered events, as well as a curve for the total population of individual events. In this approach, non-clustered events can be interpreted as the response to isolated storms. For clustered and non-clustered morphological events the expected storm demand for a 50-year return period is approximately 25% greater than that for individual events. Alternatively, for clustered and non-clustered events the magnitude of the storm demand that occurs at a return period of 17 years is the same as that which occurs at a return period of 50 years for individual events. However, further analysis shows that for a 50-year return period, the expected storm demand for the population of non-clustered events is similar to that of the clustered events, although the size of the population of the latter is much greater. Hence, isolated storms can generate the same storm demand as storm clusters, but there is a much higher probability that a given storm demand is generated by a morphologically clustered event. Appeared online in Coastal Engineering Volume 168, September 2021.

This is a subset of Geoscience Australia's Marine Connectivity Database (<a href="https://pid.geoscience.gov.au/dataset/ga/82692">here</a>), covering the North-west marine planning region for initial releases taking place in the interval January-March 2010. The subset is intended for use in development and testing as part of the GovHack 2016 competition.

In November, 2018 a workshop of experts sponsored by UNESCO’s Intergovernmental Oceanographic Commission was convened in Wellington, New Zealand. The meeting was organized by Working Group (WG) 1 of the Pacific Tsunami Warning System (PTWS). The meeting brought together fourteen experts from various disciplines and four different countries (New Zealand, Australia, USA and French Polynesia) and four observers from Pacific Island countries (Tonga, Fiji), with the objective of understanding the tsunami hazard posed by the Tonga-Kermadec trench, evaluating the current state of seismic and tsunami instrumentation in the region and assessing the level of readiness of at-risk populations. The meeting took place in the “Beehive” Annex to New Zealand’s Parliament building nearby the offices of the Ministry of Civil Defence and Emergency Management. The meeting was co-chaired by Mrs. Sarah-Jayne McCurrach (New Zealand) from the Ministry of Civil Defence and Emergency Management and Dr. Diego Arcas (USA) from NOAA’s Pacific Marine Environmental Laboratory. As one of the meeting objectives, the experts used their state-of-the-science knowledge of local tectonics to identify some of the potential, worst-case seismic scenarios for the Tonga-Kermadec trench. These scenarios were ranked as low, medium and high probability events by the same experts. While other non-seismic tsunamigenic scenarios were acknowledged, the level of uncertainty in the region, associated with the lack of instrumentation prevented the experts from identifying worse case scenarios for non-seismic sources. The present report synthesizes some of the findings of, and presents the seismic sources identified by the experts to pose the largest tsunami risk to nearby coastlines. In addition, workshop participants discussed existing gaps in scientific knowledge of local tectonics, including seismic and tsunami instrumentation of the trench and current level of tsunami readiness for at-risk populations, including real-time tsunami warnings. The results and conclusions of the meeting are presented in this report and some recommendations are summarized in the final section.

Offshore Probabilistic Tsunami Hazard Assessments (offshore PTHAs) provide large-scale analyses of earthquake-tsunami frequencies and uncertainties in the deep ocean, but do not provide high-resolution onshore tsunami hazard information as required for many risk-management applications. To understand the implications of an onshore PTHA for the onshore hazard at any site, in principle the tsunami inundation should be simulated locally for every scenario in the offshore PTHA. In practice this is rarely feasible due to the computational expense of inundation models, and the large number of scenarios in offshore PTHAs. Monte-Carlo methods offer a practical and rigorous alternative for approximating the onshore hazard, using a random subset of scenarios. The resulting Monte-Carlo errors can be quantified and controlled, enabling high-resolution onshore PTHAs to be implemented at a fraction of the computational cost. This study develops novel Monte-Carlo sampling approaches for offshore-to-onshore PTHA. Modelled offshore PTHA wave heights are used to preferentially sample scenarios that have large offshore waves near an onshore site of interest. By appropriately weighting the scenarios, the Monte-Carlo errors are reduced without introducing any bias. The techniques are applied to a high-resolution onshore PTHA for the island of Tongatapu in Tonga. In this region, the new approaches lead to efficiency improvements equivalent to using 4-18 times more random scenarios, as compared with stratified-sampling by magnitude, which is commonly used for onshore PTHA. The greatest efficiency improvements are for rare, large tsunamis, and for calculations that represent epistemic uncertainties in the tsunami hazard. To facilitate the control of Monte-Carlo errors in practical applications, this study also provides analytical techniques for estimating the errors both before and after inundation simulations are conducted. Before inundation simulation, this enables a proposed Monte-Carlo sampling scheme to be checked, and potentially improved, at minimal computational cost. After inundation simulation, it enables the remaining Monte-Carlo errors to be quantified at onshore sites, without additional inundation simulations. In combination these techniques enable offshore PTHAs to be rigorously transformed into onshore PTHAs, with full characterisation of epistemic uncertainties, while controlling Monte-Carlo errors. Appeared online in Geophysical Journal International 11 April 2022.

The Northern Approaches to Broome multibeam survey was acquired for the Australian Hydrographic Office (AHO) onboard the MV Bhagwan K during the period 05 August– 02 October 2020. This was a contracted survey conducted by EGS as part of the Hydroscheme Industry Partnership Program. The survey area encompasses the northern approaches to Broome, WA located between the Talboys Rock and Gantheaume Point, Western Australia. Bathymetry data was acquired using a Kongsberg EM2040D 200-400 kHz and processed using QPS QINSy 9.2.3 processing software. The dataset was then exported as a 30m resolution, 32 bit floating point GeoTIFF grid of the survey area. <BR>This dataset is not to be used for navigational purposes.

<p>This resource contains multibeam backscatter data for Bynoe Harbour collected by Geoscience Australia (GA), the Australian Institute of Marine Science (AIMS) and the Northern Territory Government (Department of Environment and Natural Resources) during the period between 3 and 27 May 2016 on the RV Solander (survey SOL6187/GA0351). This project was made possible through offset funds provided by INPEX-led Ichthys LNG Project to Northern Territory Government Department of Environment and Natural Resources, and co-investment from Geoscience Australia and Australian Institute of Marine Science. The intent of this four year (2014-2018) program is to improve knowledge of the marine environments in the Darwin and Bynoe Harbour regions by collating and collecting baseline data that enable the creation of thematic habitat maps that underpin marine resource management decisions. <p>The specific objectives of the survey were to: <p>1. Obtain high resolution geophysical (bathymetry) data for Bynoe Harbour; <p>2. Characterise substrates (acoustic backscatter properties, grainsize, sediment chemistry) for Bynoe Harbour; and <p>3. Collect tidal data for the survey area. Data acquired during the survey included: multibeam sonar bathymetry and acoustic backscatter; physical samples of seabed sediments, underwater photography and video of grab sample locations and oceanographic information including tidal data and sound velocity profiles. <p>This dataset comprises multibeam backscatter data. A detailed account of the survey is provided in: Siwabessy, P.J.W., Smit, N., Atkinson, I., Dando, N., Harries, S., Howard, F.J.F., Li, J., Nicholas W.A., Picard, K., Radke, L.C., Tran, M., Williams, D. and Whiteway, T. 2016. Bynoe Harbour Marine Survey 2016: GA4452/SOL6432 – Post-survey report. Record 2017/04. Geoscience Australia, Canberra. http://dx.doi.org/10.11636/Record.2017.004.

The Australian Bathymetry and Topography (AusBathyTopo) Torres Strait dataset contains depth and elevation data compiled from all available data within the Torres Strait into a 30 m-resolution Digital Elevation Model (DEM). The Torres Strait lies at the northern end of the Great Barrier Reef (GBR), the largest coral reef ecosystem on Earth, and straddles the Arafura Sea to the west and the Coral Sea to the east. The Torres Strait area is bounded by Australia, Indonesia and Papua New Guinea. Bathymetry mapping of this extensive reef and shoal system is vital for the protection of the Torres Strait allowing for the safe navigation of shipping and improved environmental management. Over past ten years, deep-water multibeam surveys have revealed the highly complex continental slope canyons in deeper Coral Sea waters. Shallow-water multibeam surveys conducted by the US-funded Source-to-Sink program revealed the extensive Fly River delta deposits. Airborne LiDAR bathymetry acquired by the Australian Hydrographic Office cover most of the Torres Strait and GBR reefs, with coverage gaps supplemented by satellite derived bathymetry. The Geoscience Australia-developed National Intertidal DIgital Elevation Model (NIDEM) improves the source data gap along Australia’s vast intertidal zone. We acknowledge the use of the CSIRO Marine National Facility (https://ror.org/01mae9353 ) in undertaking this research.” The datasets used were collected by the Marine National Facility on 13 voyages (see Lineage for identification). All source bathymetry data were extensively edited as point clouds to remove noise, given a consistent WGS84 horizontal datum, and where possible, an approximate MSL vertical datum. The 30 m-resolution grid is a fundamental dataset to underpin marine habitat mapping, and can be used to accurately simulate water mixing within a whole-of-GBR scale hydrodynamic model. This dataset is not to be used for navigational purposes.

The Great North Channel Torres Strait Multibeam survey was acquired for the Australian Hydrographic Office (AHO) onboard the MV Offshore Guardian and MV Special Order during the period 04 February– 14 April 2021. This was a contracted survey conducted by Guardian Geomatics as part of the Hydroscheme Industry Partnership Program. The survey area encompasses the Great North East Channel of the Torres Strait located between the Stephens Island, Pearce Cay and Rennel Island, Queensland. Bathymetry data was acquired using a Kongsberg EM2040-07 and Norbit iWBMSh Stx 200-400 kHz and processed using CARIS HIPS & SIPS 11.3 processing software. The dataset was then exported as a 30m resolution, 32 bit floating point GeoTIFF grid of the survey area. <BR>This dataset is not to be used for navigational purposes.