LOS ANGELES — Sea levels in California are set to rise by as much as a foot (30 centimetres) in the coming days as an enormous wave washes up the US West Coast.

The huge surge of energy, known as a “coastal trapped wave” or a “Kelvin wave,” is part of El Nino, a months-long phenomenon in the Pacific Ocean that scientists say could generate powerful storms and floods in some parts of the world, while leaving others in drought.

The Kelvin wave is not anything like a tsunami; nor does it crash on beaches. Rather it is a sustained bulge of excess water up to 30 kilometres wide that will hug the coastline as it travels all the way up to Alaska.

Dillon Amaya, an oceanographer at North Carolina State University, said the elevated sea levels could collide with other natural phenomena to create problems for coastal communities.

“What this wave is doing is it’s raising sea states, and then when... you combine this wave with things like storm surge from passing weather, large swells, or things like astronomically high tide... (you) elevate your risk for things like flooding and also beach erosion,” Amaya told AFP by telephone.

“The general rule of thumb is that every two to four inches (5-10 centimetres) of sea level rise that we see in that background state essentially doubles your flood risk.

“So it doesn’t sound like a lot, but because it’s over a huge volume of water, and it’s combined with these other factors, you start to get the flood risk.”

In recent weeks parts of Southern California have been hit by storm surges that have eaten away at beaches or damaged properties.

In Dana Point and Laguna Beach, south of Los Angeles, several houses have been left uninhabitable, and at least one has completely collapsed.

In Malibu, an enormous sink hole emerged in the driveway of a home belonging to Hollywood actor Nicolas Cage when pounding waves from a nearby hurricane eroded the coastline.