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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 ...

Frank Baumann has watched with professional interest, and a sense of alarm, as one natural disaster after another has hit British Columbia this summer.

Over the course of a few catastrophic weeks, a flash flood washed away vehicles and homes in Sicamous, a debris flow killed four people in Johnsons Landing, and then another raced through the middle of Fairmont Hot Springs, miraculously missing crowds of shocked tourists.

“I heard the Premier saying on the news the other day that none of this was predictable. But you know, that’s absolute BS,” said Mr. Baumann, a geological engineer who makes his living advising government and industry on the hazards posed by B.C.’s steep terrain.

He is not claiming that experts like him can predict when specific landslides will occur, any more than they can say when a tsunami or earthquake will strike. But the flurry of natural disasters that has struck this year, mostly in southeast B.C., are part of a long continuum of events that stretches into the distant past – and will continue into the future, he said.

In B.C., slides and floods have always poured down out of the mountains. Tsunamis have always been, and always will be, a threat on the coast. And earthquakes are simply part of the natural order of things for a province that sits nearly atop two colliding tectonic plates. But if you identify the hazards, Mr. Baumann said, you can predict when the most dangerous times and places are for people to be, and take measures to mitigate the risks.

As a case in point, he refers to the Mount Meager landslide, which came thundering down a steep volcanic mountain near Pemberton, just north of Whistler, in the summer of 2010.

A short time before that event, the BC Forest Service had adopted recommendations made by Mr. Baumann to close campgrounds in the area when there were several successive hot days.

After studying the impact of glacial melt on unstable slopes, Mr. Baumann worked out a formula that predicted the slide risk would go up whenever there were more than five days of 26-degree weather.

“When that event happened [the Forest Service] had just closed the valley because the threshold had been met and the only people up there had snuck in,” he said. “If that hadn’t been the case, the campground would have been full and there probably would have been 50 deaths.”

A few hikers were in the valley, but what may have been the biggest slide in Canadian history rumbled to a halt without harming anyone.

Mr. Baumann credits the government for doing work along the Sea-to-Sky Highway to identify creeks that were prone to flash floods. That study was spurred by a series of washouts during the 1980s, including one that took out a bridge at night, causing five vehicles to plunge into an abyss, killing nine people.

“They identified the hazard, and they build catchment basins,” he said. “You still get those debris torrents, but they are stopped before they reach the highway or houses below. So we’ve taken these natural events and have managed them.”

But not enough work is being done to identify the hazards, he said, and too often local governments give in to pressure from developers to build in areas that are at risk.

“There is constant pressure,” he said, to allow development on the limited amount of flat land found in mountainous B.C.

A paper on landslide hazards along the Sea-to-Sky corridor – written by Andrée Blais-Stevens of the Geological Survey of Canada, and Oldrich Hungr, Earth and Ocean Sciences at the University of British Columbia – comments on the difficulty posed by that dynamic.

“Overestimation of the risks … estranges developable land which is rare and extremely valuable in this mountainous terrain. Underestimation of the risk could, of course, lead to major disasters,” the authors state.

Greg Utzig, a soil specialist who owns a cabin in Johnsons Landing, said climate change is altering the risk factor across the province, bringing not only more rain annually, but also more intense rainstorms. He said the government should be doing more work to assess and mitigate risks.

A City of Vancouver report on climate change adaptation, which was released this week, underscores that concern. “Scientists project that Vancouver will experience increased annual precipitation and temperatures, with hotter, drier summers. More intense and frequent rain and wind storms are anticipated and sea level rise may pose a significant challenge by mid-century,” it states.

Among other things, the report calls for a complete flood risk assessment, both along the coast and on the Fraser River.

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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