Darwin Harbour Habitat Mapping Program: Predicted seabed gravel content

Brief description

This resource contains a predicted seabed gravel content grid for the greater Darwin Harbour region as part of a baseline seabed mapping program of Darwin Harbour and Bynoe Harbour. This project was funded through offset funds provided by an INPEX-led Ichthys LNG Project to the Northern Territory Government's Department of Environment and Natural Resources (NTG-DENR) with co-investment from Geoscience Australia (GA) and the Australian Institute of Marine Science (AIMS). The intent of this 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 and information to underpin marine resource management decisions. The predicted seabed gravel content grid was derived from a compilation of multiple surveys undertaken by GA, AIMS and NTG-DENR between 2011 and 2017, including GA0333 (Siwabessy et al., 2015), GA0341 (Siwabessy et al., 2015), GA0351/SOL6187 (Siwabessy et al., 2016), GA4452/SOL6432 (Siwabessy et al., 2017), GA0356 (Radke et al., 2017), and GA0358 and GA0359 (Radke et al., 2018), adding to those from a previous survey GA0333 collected by GA, AIMS and NTG-DENR. This dataset provides spatially continuous predictions of seabed %gravel (>2000 µm) content for the Darwin and Bynoe harbour region, northern Australian marine margin. Data are presented in 10 m resolution raster grids format and ascii text file. Predictions are based on 395 samples and 14 environmental variables derived from high resolution multibeam sonar bathymetry and backscatter data. Accuracy of predictions is high, with a VEcv = 59% for gravel; and the predictive accuracy has been increased by 68.4% for gravel in comparison with the commonly used method (i.e., IDW). Absences in predictions occur in this dataset as a result of non-availability associated with predictive variables. This dataset supersedes previous predictions of mud content for the Darwin and Bynoe harbour region with demonstrated improvements in predictive accuracy.

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Maintenance and Update Frequency: asNeeded

Statement: Sediment samples were exported from Geoscience Australia’s Marine Sediments database (MARS). These samples and relevant high resolution multibeam sonar bathymetry and backscatter data were collected during marine surveys GA0356 (Radke et al., 2017), GA0358 and GA0359 (Radke et al., 2018), GA0351/SOL6187 (Siwabessy et al., 2016) and GA4452/SOL6432 (Siwabessy et al., 2017). Predicting the spatial distribution of gravel content at 10 m resolution was undertaken using the average of the hybrid method of random forest and ordinary kriging (rfok) and the hybrid method of random forest and inverse distance weighting (RFOKRFIDW). All predictions were generated using the R package, spm (Li, 2018). The spatial predictive models used were selected from the methods in spm based on their predictive accuracy for each sediment type. This dataset is published with the permission of the CEO, Geoscience Australia.
References:
Li, J., 2018. spm: Spatial Predictive Modelling. R package version 1.1.0. https://CRAN.R-project.org/package=spm.
Radke, L., Smit, N., Li, J., Hunt-Lew Fatt, K., Harries, S., Windsor, J., Nicholas, T., 2018. Benthic Sediment surveys of inner Darwin Harbour and shallow water areas in and around Bynoe Harbour (2018) - GA0358 and GA0359 – Post-survey report.
Radke, L., Smit, N., Li, J., Nicholas, T., Picard, K., 2017. Outer Darwin Harbour Shallow Water Sediment Survey 2016: GA0356 – Post-survey report: Record 2017/06. Geoscience Australia, Canberra. http://dx.doi.org/10.11636/Record.2017.006.
Siwabessy, J., Smit, N., Atkinson, I., dando, N., Harries, S., Howard, F.J.F., Li, J., Nicholas, W.A., Potter, A., Radke, L., Tran, M., Williams, D., Whiteway, T., 2016. Outer Darwin Harbour Marine Survey 2015: GA0351/SOL6187 Post-survey report: Geoscience Australia Record 2018/08. Geoscience Australia, Canberra, ACT, Australia., p. 117.
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., Whiteway, T., 2017. 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.