The flood threat to Sydney is already three times greater than a century ago, and it will triple with every 10cm the sea level rises, according to a report from the Climate Council.

Across the country almost 250,000 homes worth about $72 billion are vulnerable to a 1.1m rise in sea levels, with one-quarter of them in NSW.

“Australia is highly vulnerable to increasing coastal flooding because our cities, towns and critical infrastructure are mainly located on the coast,” the report says. “Australia’s infrastructure has been built for the climate of the 20th century and is unprepared for rising sea levels.”

If the sea rises 50cm, flood events now expected to occur once in 100 years could hit every few months, according to the report.

If carbon emission levels remain on their current trajectory, Sydney, Bundaberg and Hobart will experience such events every day or so by the end of this century, it warns.

About 52% of the country’s coast is vulnerable to recession as rising seas, backed by storm surges, eat into sandy or muddy shores. About 40% of the NSW coast is vulnerable.

Infrastructure worth about $226 billion is at risk nationwide, even before population and economic growth add to the number of homes and cost of assets.

In southeast Queensland the cost of coastal flooding could double by 2030 and quadruple by 2070.

“We need deep and urgent cuts in greenhouse gas emissions this decade and beyond if we are to avoid the most serious risks from rising sea levels and coastal flooding,” the report says.

Globally, sea level rises of 40-100 centimetres are expected by the end of the century.

Socioeconomic change alone is expected to push average flood losses in the world’s coastal cities to $US52 billion ($57.89 billion) a year by 2050, the report says.

If no adaptation measures are implemented and land subsidence and sea level rises are taken into account, the projected flood losses rise to $US1 trillion ($1.11 trillion) a year.

The Sydney-based Climate Council is an independent non-profit organisation. Formerly known as the Climate Commission, it was disbanded as a federal body by the Abbott Government.