Insights for impact Preparing for coastal disasters: What happens when tsunamis strike Australia?

The challenge

When a tsunami warning is issued, emergency managers may have only hours — sometimes less — to make decisions that affect entire coastal communities. Which areas should evacuate? Which roads may become inaccessible? Which ports, marinas and low-lying neighbourhoods are most at risk?

Unlike a bushfire, which typically spreads over time, a tsunami can affect hundreds of kilometres of coastline within hours, leaving little time to move people and assets out of harm's way.

Traditionally, evacuation planning has relied on broad hazard zones, such as identifying all areas within one kilometre of the coast and less than 10 metres above sea level. These zones can encompass large populations and extensive infrastructure, creating evacuation demands that may exceed the capacity of emergency services.

More targeted planning depends on something most people never see: the shape of the seabed and coastal landscapes beneath the water.

From offshore earthquake to onshore impact

Most tsunamis are generated by undersea earthquakes. The 2011 Tōhoku earthquake and tsunami in Japan, which claimed nearly 20,000 lives, was a powerful reminder of the importance of understanding coastal hazards before disaster strikes.

As tsunami waves travel across the ocean, they are shaped by the seabed and coastline. Continental shelves, submarine canyons, reefs, harbour entrances, estuaries and coastal landforms can all influence wave height, speed and the extent of coastal inundation.

Understanding these interactions requires detailed modelling — and detailed modelling depends on high-quality bathymetry, elevation and coastal data.

Constructing a clearer view of Australia's coast

Around Australia, Geoscience Australia and its partners are improving the information used to model tsunami hazards and coastal inundation.

By combining high-resolution seabed mapping, elevation data and advanced probabilistic modelling based on thousands of potential earthquake scenarios, scientists can estimate tsunami wave heights, flow speeds, inundation extents, and even arrival times.

This work relies on data, products and infrastructure from across Geoscience Australia, including:

• The AusSeabed Marine Data Portal, which improves discovery and access to marine data collected by governments, researchers and industry.
• The ELVIS Elevation Information System, which provides access to national elevation datasets, including high-resolution LiDAR-derived terrain information.
• The national AusBathyTopo grids bring marine and terrestrial elevation data together into seamless bathymetry-topography products.

Supporting critical action plans

Improved tsunami modelling is already supporting emergency planning in Queensland, New South Wales and Western Australia.

In Queensland, detailed inundation modelling developed for the Gladstone region is helping inform tsunami evacuation planning and improve understanding of potential impacts to communities and infrastructure.

In New South Wales, Geoscience Australia and the NSW State Emergency Service developed tsunami inundation modelling for the entire NSW coastline, including many areas where detailed assessments had not previously been available.

In Western Australia, modelling from Geraldton to Dunsborough supported work with the Department of Fire and Emergency Services to improve tsunami evacuation mapping and planning.

These projects help emergency managers better understand where hazards may emerge, how severe impacts could be, and how communities may need to respond under different warning conditions.

More than a hazard model

Marine and coastal data collected for one purpose often delivers value far beyond its original application.

The data used to model tsunamis also supports coastal resilience, environmental management and infrastructure planning. By reusing bathymetry, elevation and geospatial information, we can better understand hazards such as storm surges, erosion and inundation while delivering broader value from existing datasets.

Blue geoscience for better decisions

With more than 87 per cent of Australians living within 50 kilometres of the coast, high-resolution seabed and elevation data underpins decisions that affect communities, infrastructure, industries and ecosystems around the nation.

By integrating data from many sources and partners, Geoscience Australia is equipping emergency managers for better preparedness, more targeted responses and a stronger understanding of risk before the next warning is issued.