El Nino, La Nina pose double whammy for B.C. coast

Victoria and Esquimalt residents may have to batten down the hatches as El Nino and La Nina weather systems make their way here.

  • Sep. 25, 2015 12:00 p.m.

— Pamela Roth

Victoria and Esquimalt residents may have to batten down the hatches this winter as El Nino and La Nina weather systems make their way to the West Coast.

Ian Walker, a geology professor at the University of Victoria, is an expert when it comes to coastal erosion and sea level trends. His research has taken him from Haida Gwaii to California, and he recently co-authored a new study on El Nino and La Nina.

According to Walker, coastal communities need to prepare for the possibility of extreme flooding, and erosion that comes with both weather systems. Low lying areas in Victoria and Esquimalt or those living close to coastal bluffs could see a greater chance of flooding, erosion or road closures with the arrival of storm season this year.

“We won’t really know until December or January, but all indications are that it’s going to be a very extreme one (El Nino),” said Walker. “It can’t help to be prepared and I think that’s the important take home message.”

El Nino is a natural ocean temperature phenomenon that results in warmer than average coastal waters near the equator that move towards South America’s northern coast, then turn as far north as Haida Gwaii and Alaska. Because the waters are warmer, Walker said their levels are higher due to thermal expansion. Some areas up the coast have seen as much as 40 cm to 70 cm of additional water.

La Nina is the opposite of El Nino, explained Walker, and usually follows some time after. During La Nina, the storm track that usually sits over Washington and Oregon shifts northwest to Vancouver Island, producing stronger winds and bigger waves, but average ocean levels are lower. A significant La Nina in 2011 and 2012 created lots of wind damage and coastal erosion.

Walker said 1997/1998 and 1982/1983 were the most extreme seasons thus far because of the two weather systems, and this year is shaping up to be close to that or even more extreme.

“Based on what we’ve seen in California we know that these El Nino years translate into higher ocean levels,” said Walker. “Even the average winter storm can have a greater impact because of the higher ocean levels.”

Researchers from 13 different institutions, including the University of Victoria, recently conducted a study that analyzed wave, water level and shoreline response data to identify the impacts of both El Nino and La Nina in coastal regions across the Pacific Ocean.

The study marked the first to show how the two climate events are linked to greater erosion and flooding in coastal regions, and was published this week in Nature Geoscience.