Some scientists at an international symposium in Vancouver warn most estimates for a rise in the sea level are too conservative and several B.C. communities will be vulnerable to flooding unless drastic action is taken.

The gathering of the American Association for the Advancement of Science heard Sunday the sea level could rise by as little as 30 centimetres or as much as one metre in the next century.

But SFU geology professor John Clague, who studies the effect of the rising sea on the B.C. coast, says a rise of about one metre is more likely.

He said that's serious enough to threaten the communities of Richmond and Delta, including homes, Vancouver's international airport, Deltaport and theTsawwassen ferry terminal.

Estimates for the rise in the sea level range from 30 centimetres to five metres by the end of the century. (Jonathan Hayward/Canadian Press)

"We're going to see people either defending property, spending tremendous amounts of money trying to defend coastal properties, or we need to relocate the peripheries of our cities to higher elevations," said Clague.

While the sea level has remained relatively constant during the past 5,000 years, it has been rising over the past 100 to 200 years, and Clague says melting glaciers and a warmer ocean that occupies more space are to blame.

"One of the most famous atmospheric scientists, James Hansen, is arguing we could be facing five-metre higher sea levels by the end of the century, and he's not a flake, he's a very renowned scientist," said Clague.

Higher dikes, houses on stilts

That's a drastic scenario that most scientists feel is unlikely, but if true, would force the abandonment of Richmond, says Clague.

Clague says building defences like protective dikes are costly, but retreat may not be an option in major cities like Vancouver or Seattle.

UBC researcher David Flanders says people living in low-lying communities have several options when it comes to protecting their properties from a rising sea, including building barrier islands in inter-tidal zones to reduce the impact of winds and waves during storms.

Residents of communities like Delta could also build higher dikes or implement unique architectural solutions, like building homes on stilts or even moving entire communities, says Flanders.

Margaret Davidson of the U.S. National Oceanic and Atmospheric Administration said the problem could impact as many as 500 million people worldwide.

A 2011 report from the B.C. government warned builders and developers to plan for a one-metre rise in the sea level within the next 90 years.