Offshore mapping

We love our coasts in NSW, but what lies behind the waves? Little is known about the deeper seabed along the NSW coast. We are exploring these offshore waters to better understand the character of the coastal zone, the processes that shape it and to help inform its management.

What do we do?

We collect detailed information on the seabed along the coast of NSW. This includes high-resolution 3D elevation surfaces of the seafloor (digital elevation models) and data which reveal what the seabed is made of. This includes maps of seabed reflectivity (backscatter), sediment samples and underwater imagery.

Why is this important?

Sponges on the seabed showing 'Erect Sponges' – branching blue and yellow and rounded orange sponge typesThe collection of seabed data is critical for almost every aspect of coastal and marine management. In order to manage an area, it helps to know what is there. An understanding of what type of seabed there is, what it is made of and what is living there is critical so we can better manage coastal hazards and risk for NSW and ensure there are viable and healthy marine ecosystems for the future.

Detailed information on the seabed character and composition is important for management of coastal hazards, erosion and wave prediction models as well as marine planning, monitoring, research and emergency response.

Mapping the distribution of sediments across the seafloor can show how sediment moves around and between beaches, and can help to understand the processes behind sediment transport. Mapping the distribution of organisms on reefs and sediments can reveal the biodiversity of marine life within an area which is needed for marine conservation planning.

SeaBed NSW

We recently started a 4-year project, SeaBed NSW, to collect data on the structure and composition of the seabed adjacent to our beaches. This new program was funded as part of the NSW Coastal Reforms package and aims to provide a deeper understanding of the coast and seafloor to assist with coastal management.

The program builds on the research expertise and specialist capabilities OEH developed back in 2005 as part of the HABMAP program mapping seabed habitats of our marine estate. To date, our offshore mapping has covered some 15% of state coastal waters. This new project will map large areas of the seafloor on the inner continental shelf using airborne laser mapping (LADS) in shallow water depths and vessel-based multi-beam sonar further offshore. The seabed map will then be validated or ‘cross-checked’ by collecting and analysing sediment (grab) samples using specialist equipment onboard our research vessel RV Bombora.

The program is a major boost to our eventual goal of a continuous high-resolution digital elevation model (DEM) for the entire NSW coast. The data will: build significantly on our existing database; provide a more accurate 3D surface for our wave modelling tools (see links below); enable us to answer questions about how sand moves around the coastal-marine environment and provide baseline information from which to measure change.

Seafloor data

So, what’s down there? Are there reefs? Is there sand or mud? And how do these features vary from beach to beach and region to region?

The data we collect allows us to visualise the seafloor in a level of detail that no-one else has ever seen before.

Explore more of our Wollongong sea floor data in this innovative story map.

How do we do it?

We use different technologies to `see through’ the water column, map the seabed and collect basic information on the nature of the seafloor.

Sonar

We use sonar equipment mounted on our research vessels Bombora and Sea Scan, as well as jet skis and quad bikes. Sonar systems bounce sound (much like a fish-finder) off the seabed to determine seabed depth and reflectivity. Each wave of sound is called a ‘ping’. Systems which release single pings are called “singlebeam” sonars.  Systems which use multiple pings (beams) are called “multibeam” sonars and release sound in a fan-shape or ‘swath’ up to 200-300m wide. Pings of sound are generated up to 10–15 times a second.

Aerial photography and lasers

Through partnerships we access airborne mapping with lasers (marine LiDAR) mounted on small planes to collect detailed seabed maps of depth and reflectivity from the nearshore zone from the beach to depths of 20 to 30 m. We also use aerial photography to identify areas of reef and sand where the water is shallow and clear.

Video data

To investigate the diversity of the marine life across the states reefs and soft sediments we collect underwater video footage by towing a camera close to the seabed. This data allows us to: validate the seabed maps from the sonar with actual ‘visual’ samples identify the organisms living on or near the seafloor and characterise benthic reef communities.

Sediment data

We collect sediment samples of the seabed to help us understand the composition of the seabed surface. Our sampling system, called a ‘grab sampler’ acts like a jaw which snaps shut when it reaches the seabed and brings us a sample of the sediment. Understanding whether the sediment is sand, mud or gravel is important as this tells us how the sediment may move around within a beach and between beaches.

SeaBedNSW and HABMAP programs data