IT is only a matter of time before a "catastrophic" 197ft tsunami slams into Australia and causes miles of inland destruction, experts have warned.

Coastal cities like Sydney could be drowned by a wall of water before it potentially roars 31 miles inland, it has been suggested.

Tsunamis are commonly known to be triggered by earthquakes and underwater landslides, but the devastating events can also be caused by large meteor strikes, which are harder to detect.

Dale Dominey-Howes, co-director of the Australian Tsunami Research Centre at the University of New South Wales said tsunamis posed a real threat to Australian cities.

He told the Australian Geographic: "If it occurred without warning on a Saturday afternoon in summer the impacts would be catastrophic.

"I suspect it's only a matter of time before we are affected by something damaging.

Tsunami expert Dr Ted Bryant, formerly of the University of Wollongong, believes detection systems would likely fail to pick up an incoming comet or meteor which could send enormous waves heading towards populated coastal areas.

Dr Bryant found evidence that monumental tsunamis have wreaked havoc across the east coast of Australia throughout history, the Mail online reports.

He believes a tsunami hit the Shoalhaven delta near Nowra on the New South Wales South Coast between 4,000 and 5,000 years ago, sending water 10km inland. There is also evidence to suggest a colossal tidal wave from a tsunami once reached the country's famous Blue Mountains, which lie 31 miles inland.

The most recent tsunami to hit Oz was in 1491 - it was recorded to measure 197ft high but did not travel as far from the coast according to Dr Bryant.

Coastline authorities monitor activity 24-hours-a-day for incoming tsunamis. They usually detect one every two years.