In Sydney, reclaimed land is the most exposed to the threat of rising sea levels, especially that on the edge of Botany Bay, which includes Kingsford Smith Airport and Port Botany.

"The good news is that we have plenty of time to elevate these areas," said Sydney University professor Andrew Short, who is an expert in coastal systems.

"We have decades, if not a century or more, during which time you can elevate the existing infrastructure to levels that they would not be inundated."

While it does not sit on reclaimed land, the suburb of Brighton le Sands on the shores of Botany Bay in the city's south was one of the more vulnerable because of its low elevation.

"It is an area that in some time in the future would require elevating," Professor Short said.

Analysis based on a report from US group Climate Central has found about 1.9 million people in Australia live in areas that would be submerged if there was an 8.9 metre rise in sea level. At 4.7 metres, it would be 668,000 people.

The analysis assumes that global warming by 4 degrees could lead to 8.9 metres of long-term sea level rise in the centuries to follow.

Professor Short said sea levels were already rising at about 3 millimetres a year, and cautioned that the scenarios in the report were at the "extreme level".

Rockdale City Council said it was "actively managing" foreshore at Lady Robinsons Beach by installing sea walls and rock groynes as part of efforts to help reduce tidal erosion.

The areas most susceptible to flooding included the Rockdale wetlands corridor, areas around Wolli Creek and land near Sandringham.

"These areas have previously experienced damage from storms and associated rain events. If sea levels rise, these impacts would be exacerbated," a council spokesman said.

However, the council did not believe Brighton le Sands was any more vulnerable to rising sea levels than many other coastal areas around the country.

While airports and ports are usually at higher elevations, experts say it is the threat to roads and railway lines from rising sea levels that is often overlooked.

Mark Baker-Jones, a partner at law firm DibbsBarker who specialises in climate change, said roadways were often the "weak link" in "climate proofing" key assets in Australian cities.

"Climate change has often been taken into account when building new runways ... but there is no point flying there if your passengers can't get in or out of the airport," he said.

"One break in the chain can affect the whole thing. As climate changes, so do the consequences of that change. You can't just have a climate change plan and say you are safe for 20 years."

Flooding in Bangkok has highlighted the impact on businesses, workers and residents.

In 2011, technology giant Apple faced a large bill not because its factory in the Thai capital was seriously damaged but because workers were unable to reach it due to impassable streets.

A spokeswoman for Sydney Airport said it "actively considers" the impact of climate change across a range of areas, and takes into account flood studies and forecasts.