High-resolution depth model for the Great Barrier Reef and Coral Sea
There is a critical lack of information about the location and extent of deep-water ecosystems and seabed habitats for about a third of the Great Barrier Reef World Heritage Area that lies deeper than 200 m. In addition most of the inter-reefal (or between reefs) seabed shallower than 200 m on the Great Barrier Reef shelf, and many of the coral reefs themselves, have never been adequately mapped using modern echosounder techniques.
Figure 1. Results of multibeam mapping
Therefore key seabed geomorphic features, such as shoal habitats and submerged reefs, which help define the spatial boundaries of deep-water ecosystems, remain largely hidden from view and outside of effective Marine Park management. A new and detailed 3D seabed map of the Great Barrier Reef (GBR) and Coral Sea is needed as a fundamental mapping tool to help inform managers and marine scientists.ject 3D-GBR area
In recent years there has been a vast increase in the amount of digital depth data obtained in the GBR and Coral Sea through a series of research vessel ocean mapping expeditions using multibeam sonar (Figure 1). Combined with the latest singlebeam echosounder data, satellite remote-sensing and lidar bathymetric survey results, Project 3DGBR will develop a new high-resolution depth model for the GBR and adjoining Coral Sea.
Figure 2. Map of Project 3DGBR area
The area of interest is vast: over 3 million square km, from the Gulf of Papua to northern New South Wales, and easterly into the deep Coral Sea (Figure 2 & Map below). The new 3D depth model will accurately map elevation and depth points across the area using a grid pixel size of about 100 m resolution. This means that every grid node (or centre) will be about 100 m apart, making the final depth model more detailed than any previous model. The new grid will be called 'gbr100'.
The uses of a new high-resolution depth model are numerous, such as:
To model ocean current movements through the Great Barrier Reef and Coral Sea;
To accurately predict tsunami arrival times on the east Australia coastline;
To conduct inundation modeling for sea-level rise on the coastal zone; and
To help understand ecosystem and biodiversity patterns on the seabed.
Figure 3. Example 3D map of Coral Sea
The new gbr100 grid provided by Project 3DGBR will inform the managers at the Great Barrier Reef Marine Park Authority (GBRMPA) on where are the key seabed features in the deep GBR, and how well the current network of zoning protects the range of seabed habitats identified in the new depth model. In addition, marine scientists require a detailed depth map for planning future research locations and for targeting seabed biodiversity study sites (Figure 3 & Movie below).
The project is funded through a 2009 Queensland Smart Futures Fellowship awarded to Dr Rob Beaman, with matching funds provided by the Reef and Rainforest Research Centre (RRRC) and James Cook University (JCU). Project partners include staff from the Australian Institute of Marine Sciences (AIMS), Geoscience Australia (GA), CSIRO Marine and Atmospheric Research (CMAR), and Queensland Primary Industry and Fisheries (QPIF).
Much of the source depth data for the project are provided by the Australian Hydrographic Service (AHS) using Royal Australian Navy (RAN) hydrographic survey data collected over many years. Collected primarily for navigational safety, the AHS depth data is used as vital source data in the new 3D depth model. The project partners gratefully acknowledge the assistance of the AHS and RAN staff to the project.