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The Johnsons landing landslide is shown in this Thursday July 12, 2012 handout photo. (HO/The Canadian Press)
The Johnsons landing landslide is shown in this Thursday July 12, 2012 handout photo. (HO/The Canadian Press)

Applying reason to nature’s wrath Add to ...

That’s just the type of proactive study that is needed province-wide, Mr. Baumann argues, because whether it’s rising water or falling rocks, the future clearly has more natural disasters in store for B.C. “What’s important is that we recognize the hazards,” he said, “and do what we can to manage them.”

B.C.’s Big Six Natural Hazards1) EarthquakesHotspot: Victoria and parts of Metro Vancouver, with populations of 360,000 and 2.4-million. The probability, within the next 50 years, of earthquakes powerful enough to damage buildings is 12 per cent for Vancouver and 21 per cent for Victoria. Liquefaction is an added concern in Metro Vancouver, where Richmond is most likely to be affected.

What happens: A megathrust earthquake occurs when two tectonic plates are in collision – a real threat in the Cascadia subduction zone just off B.C.’s southwest coast. When one plate thrusts under the other, enormous forces are unleashed. Liquefaction takes place when a solid soil mass becomes saturated and loses its strength.

Last big incident: A magnitude 9 megathrust earthquake in the Cascadia subduction interface struck on Jan. 26, 1700.

2) TsunamisHotspot: The outer coast of Vancouver Island is at greatest risk, notably the town of Port Alberni, where about 25,000 people live at the head of a long, narrow inlet. An underwater landslide in Georgia Strait could also unleash large waves, which could overwhelm dikes protecting Richmond, a city of 190,000.

What happens: When a powerful earthquake occurs under the ocean floor, it pushes a large volume of water to the surface, creating waves which build as they enter shallower water approaching a coast. Narrow inlets can amplify the height, speed and impact of the waves.

Last big incident: In 1964, a 9.2 magnitude earthquake in Alaska sent a tsunami along the West Coast. It damaged more than 260 buildings in Port Alberni, where the highest wave was over six metres.

3) Landslides and debris torrentsHotspot: The Sea-to-Sky corridor, which includes Squamish, Whistler and Pemberton, with a combined population of more than 30,000.

What happens: Intense rainfall on steep slopes can destabilize soil masses, and earthquakes can fracture off parts of mountains, unleashing masses of earth, rock and vegetation with little warning. When sediment slumps into streams creating temporary dams, intense debris flows can pour out suddenly.

Last big incident: In 1981, a debris torrent raced down Meager Creek, in Howe Sound, releasing 20,000 cubic metres of debris and causing 10 deaths. And this month, four people died in a debris torrent in Johnsons Landing, on Kootenay Lake.

4) FloodsHotspot: Communities in the Fraser Valley, including much of Metro Vancouver, which has a combined population of about 2.4 million. Although there is a major dike system in place, many areas around Chilliwack, Mission and Hatzic remain vulnerable; provincewide, more than 200 communities are located on floodplains.

What happens: It usually takes a combination of a heavy snowpack, a sudden melt and intense rainfall to produce floods.

Last big incident: This spring the Fraser River reached near-historical levels, but the latest major flooding event was in June, 1948, when large areas of the Lower Mainland flooded, causing $20-million in damages.

5) Forest firesHotspot: Prince George, with a population of 71,000, may be the largest community facing major risk, because it lies in the middle of a zone where pine beetle infestation has killed a massive swath of forest.

What happens: Standing trees and a mass of fuel lying on the forest floor can create firestorms so large they generate their own wind, allowing flames to jump over fire barriers and across rivers.

Last big incident: There are massive forest fires almost every summer somewhere in B.C., but in 2003 a fire ran out of control on Okanagan Mountain, forcing the evacuation of 27,000 people and destroying 239 homes in Kelowna.

6) VolcanoesHotspot: There are three major volcanic belts in B.C. – Garibaldi, Anahim and Stikine – but they are located in relatively unpopulated areas and aren’t considered threats to any towns, although Mount Meager is only 50 kilometres from Pemberton.

What happens: Volcanoes can lie dormant for a long time, as all of those in B.C. have, but after an extended period of quiet they can become active and produce extremely large explosions, as Mt. St. Helens did when it erupted in Washington State in 1980, killing 57.

Last big incident: The Tseax River cone, at the southern end of the Stikine Volcanic Belt, erupted about 200 years ago and is thought to be Canada’s youngest volcano. Volcanoes in the Garibaldi belt, just north of Vancouver, have been sporadically active over millions of years, but the most recent eruption was at Mount Meager, which erupted 2,300 years ago.

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