A tsunami would surge through most Illawarra beachside suburbs within minutes of appearing off the coast.
Residents might get just two hours' warning if it originated near New Zealand.
Water would surge forcefully along roads and waterways, carried to low-lying areas - in some cases more than a kilometre inland.
The scenario has been used as part of animated hi-tech modelling to predict the impact of a large-scale disaster in Australia.
A national working group studying emergencies chose the region ahead of other locations for the rare simulation - not generally for public eyes.
The Mercury was granted special permission to publish stills from the four 20-minute videos.
They show a 6m wall of water surging across the ocean and onto land at Wollongong, Bellambi Point, Wollongong Harbour and the Port Kembla steelworks.
The simulations focus only on a limited section of the Illawarra. Thousands of tonnes of water gush through eastern areas, with water levels rising the fastest in Woonona, Bellambi, Corrimal, Towradgi, Fairy Meadow, Wollongong and Port Kembla.
A separate map of the potential impact zones predicts that suburbs not shown in the videos could also be affected.
These suburbs include Windang, Primbee, Kanahooka, Oak Flats, Barrack Heights, Mt Warrigal, Warilla and Lake Illawarra.
The study did not mention areas further north or south but authorities confirmed that in the event of a tsunami, people living up to 1km from the coast in Wollongong, Shellharbour, Kiama and along the South Coast could be evacuated.
Tsunami expert Ted Bryant of the University of Wollongong said such an event was safer watched from afar.
"Don't race down to Flagstaff Hill ... headlands are one of the regions prone to tsunami," he warned.
The videos were created by Geoscience Australia and the Australian National University based on topographical characteristics of the Illawarra coast and ocean floor.
They were used to study threats posed by natural hazards and to predict the possible economic and human toll.
Emergency Management Australia, which oversees state response procedures, used the modelling in its planning.
Its director-general, Tony Pearce, said the videos originally were used by the national Catastrophic Disasters Working Group as it assessed Australia's response capacity.
"They were going to look at a flood in the Nepean (west of Sydney) area as an example but it was after the 2004 tsunami and they were a bit light on for modelling disasters in NSW, which was the state they wanted to do it in," he said.
"They wanted to look at a serious scenario and they decided on a tsunami.
"The group was looking for a community along the coastline that was fairly well developed with ... industry - Wollongong seemed to fit the bill so the model was done there."
It was based on the unlikely event of a landslide in the ocean.
"The model is used to discuss the sort of problems that could occur in catastrophic events," he said.
After seeing the Wollongong model, the Western Australia Government commissioned similar models for its coast.
Illawarra-South Coast State Emergency Service said it would organise warnings in the region during the approach of a tsunami and evacuate high-risk areas such as beaches and caravan parks.
Deputy region controller Dianne Gordon said a tsunami education and evacuation plan for Illawarra would be released in November.
"People living under the 10m contour line within 500m of the coast, or 1km from the coast and in a flood plain, would be evacuated in the case of a major tsunami," she said.
Bodies such as Port Kembla Port Corporation also have a role to ensure the spread of oil or chemical spills was minimised.
The research will be used as part of the $68.9 million Australian Tsunami Warning System project, due to be fully operational by next June.