Marine acoustic mapping of turbid, macro-tidal coastal environments – a large-scale example from tropical northern Australia

Dr Rachel Nanson1, Kim  Picard1, Dr Justy Siwabessy1, Neil Smit3, David Williams2, Lynda Radke1, Brendan Brooke1, Scott Nichol1

1Geoscience Australia, Symonston, Australia, 2Australian Institute of Marine Science, PO Box 41775, Casuarina, Australia, 3Department of Environment and Natural Resources, Northern Territory Government, Palmerston, Australia


Coastal areas with highly turbid waters, such as most of northern Australia, present challenges for mapping seabed topography and habitats. In these environmental conditions multibeam sonar systems rather than LIDAR are relied upon. By integrating these data with sub-bottom profiles, critical environmental baseline information is obtained, improving our understanding of coastal processes.

Seabed mapping is a core part of a 4 year collaborative program between the Northern Territory Government, Geoscience Australia and Australian Institute of Marine Science, and has been made feasible through offset funds provided by INPEX-led Ichthys LNG Project to the Northern Territory Government Department of Environment and Natural Resource, and co-investment of the collaborators. Here, we outline some of the key insights gained from mapping the seafloor of the greater Darwin Harbour region using this integrated multibeam and sub-bottom approach.

These new data reveal both terrestrial and marine palaeo- and recent environments. Multiple geomorphic features were identified including reefs, sediment bedforms and erosional surfaces, indicating a range of contemporary processes. These features highlight the diversity of habitat that can be found in this turbid and dynamic coastal environment. These data will be used to inform management of the benthic habitats of the harbour and help guide future surveys to document and monitor the harbour’s biological communities.


As a graduate Rachel initially worked as a Rivercare Implementor for the Department of Land and Water Conservation (NSW), before returning to studies to undertake her PhD in fluvial geomorphology.  She has since been employed as a fluvial and marginal marine geomorphologist in both academic and consulting roles . Rachel has recently moved her research focus further offshore, and is today representing Geoscience Australia in her role as a marine geomorphologist.