How B.C.’s string of natural disasters are connected, While weather is naturally variable, events such as extreme heat, wildfires and flooding will become more frequent and more intense because of climate change by Kathryn Blaze Baum, Carrie Tait, Justine Hunter, and Matthew McClearn, Nov 21, 2021, The Globe and Mail

The two-lane highway between the B.C. communities of Lillooet and Pemberton is a notorious mountain pass: a ribbon of curves and switchbacks often littered with rocks and other debris dislodged from steep slopes. It’s a cellphone dead zone.

Driving was slow going late Monday morning, with motorists navigating rain, slush, snow and debris on this stretch of Highway 99, known as Duffey Lake Road. About 40 kilometres south of Lillooet, traffic hit a standstill. A mix of mud, shale, and busted trees cut across the highway, stranding dozens of motorists.

Among them was Jukka Tuisku, who was returning home to Vancouver with two friends after a weekend trip to Lillooet.They peered out at the destruction, until one friend said Mr. Tuisku’s name with the kind of urgency that indicates serious trouble. A second landslide was barrelling down the mountain. At first, it sounded like something scraping on gravel. Then, a river of muck roared in, shoving vehicles and people off the highway. Two car lengths separated Mr. Tuisku from the slide.

“It looked like the forest had just come right over the road,” Mr. Tuisku told The Globe and Mail this week. “We got out of the vehicle and ran. It was pandemonium.”

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Above them, way up in the sky somewhere over southern B.C., flowed an atmospheric river – a narrow band of moisture-laden air that brings heat and precipitation from the tropics to the poles. Atmospheric rivers can carry 25 times more water than the Mississippi River.

This one made landfall on Nov. 13, dumping record-breaking precipitation and wreaking havoc on southern B.C. … The deluge caused widespread flooding, as well as damage to roads, bridges, rail lines, energy pipelines and other vital infrastructure. At least one person died in the Duffey Lake Road slide. Several other people have been reported missing, and reports of more fatalities are expected in the coming days. Roughly a dozen other slides have caused closures on other crucial thoroughfares. On Wednesday, B.C. Premier John Horgan declared a state of emergency.

It would be an understatement to say it has been a tough few months for the country’s westernmost province. In late June and early July, a once-in-one-thousand-years heat wave blanketed the Pacific Northwest, claiming the lives of at least 595 people in B.C. alone and fuelling wildfires. It was the most deadly weather event in Canadian history.

It’s easy for laypeople to connect extreme heat to fires: high temperatures dry out vegetation, creating tinder-like conditions. But scientists will tell you that flooding and mudslides are also part of the cascade of climate-change disasters. With wildfires come changes to the soil and vegetation that can exacerbate the effects of heavy rainfall.

Lytton, the Fraser Canyon village that hit 49.6 degrees during the heat wave and then went up in flames, is a case in point: Stretches of the highway near the village were shut down because of post-wildfire mudslides or the threat of them.

The government of B.C. is well aware that the province is in the crosshairs of global warming. In 2019, the province released a preliminary climate-change risk assessment that warned of provincial-scale climate risks. That same year, the government committed to implementing a new provincial flood strategy, which has yet to be completed.

While weather is naturally variable, events such as extreme heat, wildfires and flooding will become more frequent and more intense because of climate change. All of Canada is vulnerable for different reasons and in different ways. And nowhere is adequately prepared.

Most infrastructure across the country was built for a world we no longer live in. Emergency medical systems could easily become overwhelmed in the face of a sudden and widespread calamity. Weather alert systems need to be adapted to properly communicate the severity of an event at precisely the right time.

“One of the lessons of what happened this week is that the climate is changing faster than we can adapt,” said University of British Columbia climate scientist Simon Donner. “We’re not ready for this.”

Atmospheric rivers are, put simply, rivers in the sky. They’re long (more than 2,000 kilometres), narrow by the standards of atmospheric phenomena (up to a few hundred kilometres wide) and can be up to a few kilometres deep. They occur frequently throughout western North America, bringing the kind of wet weather British Columbians are accustomed to in the fall and winter.

So when the B.C. River Forecast Centre looked at its modelling for the days before the historic rain, the mere fact that an atmospheric river was on the way wasn’t considered exceptional or alarming. “Leading up to the weekend of Nov. 13-14, 2021, there was no indication that this event was significantly different than the other heavy rainstorm/atmospheric river events that happened this fall season,” Aimée Harper, a spokesperson for Emergency Management B.C., said in an e-mail. “Atmospheric river rainfall events have a high degree of uncertainty and complexity, making accurate long-term forecasting difficult.”

Climate Scientist and Professor Simon Donner explains what the phenomenon ‘atmospheric river’ is and why the one that hit Western Canada dumped record breaking amounts of rain in the Lower Mainland of British Columbia.

After several days of warnings about rainfall, wind and snow in coastal B.C., Environment and Climate Change Canada issued a warning on the morning of Nov. 13 that specifically mentioned the atmospheric river bound for the province. “A significant atmospheric river event will bring copious amounts of rain and near-record temperatures to the B.C. south coast beginning late this afternoon,” the warning said, noting that the rain would be heaviest Sunday and could cause flash floods and water pooling on roads.

Even by noon that day, the B.C. River Forecast Centre’s modelling still showed that river flows (terrestrial rivers, not the atmospheric kind) for the south coast and Vancouver Island would be in the range of a one-in-five-year event. As it turned out, the disaster was more like a one-in-500-year event.

The atmospheric river coincided closely with other phenomena that made things worse. To begin with, much of the affected area in southern B.C. had experienced drought just months earlier, accompanied by wildfire in some cases. Those conditions reduced vegetation and primed soils for the sort of structural failure that can precede mudslides.

And the area had recently had snowfall, including at mid-elevations on mountainsides. When rain falls at temperatures hovering around freezing or higher, snow melts very quickly. Compounding matters, much of B.C. has experienced a particularly wet autumn. The soil was already saturated, reducing its ability to absorb more water.

This particular atmospheric river was notable for the sheer volume of water it carried. Sunday’s rainfall alone broke 20 records for the date, from Victoria to Yoho National Park on the Alberta border, according to Environment and Climate Change Canada.

The Lillooet area beat its 1975 record of 16 millimetres with a new record of 28 millimetres, and the Pemberton area beat its 1948 record of 33 millimetres with a new record of 39.5 millimetres. But those numbers aren’t necessarily striking when compared to areas like Hope, southeast of Pemberton. There, the old record of 35 millimetres set in 2018 was smashed by a factor of five, with rainfall measuring 174 millimetres.

When organic material burns at high intensity, water-repellent compounds are vapourized and condense on cooler soil layers below. Heavy rains run off the layer of water-repellent soil much as it would pavement, which can cause flash flooding. If the top layer becomes saturated, it can slide downhill, causing mudslides and landslides.

The downpour on Sunday swamped roads and caused extensive flooding, including in the Premier’s own home in Langford, on Vancouver Island. He spent part of the day stacking sandbags next to his house after his basement was overrun with water.

“We had a river literally running beside our house,” Mr. Horgan told The Globe. “I thought, ‘This is not supposed to be happening at this time of year.’” He was briefed by Public Safety Minister Mike Farnworth at 7:30 p.m. on the magnitude of the storm damage, but said it wasn’t until daylight the next day that the real picture emerged. “We needed the clear light of day to see the magnitude of the impacts on the highway infrastructure,” he said.

What made the Duffey Lake Road area so susceptible to a dramatic mudslide was its geography. Mudslides – or debris flows, in scientific terms – occur on gradients steep enough for rainfall to cause saturated soil to break loose from the underlying bedrock, explained University of British Columbia fluvial geomorphologist Brett Eaton.

The mountains in the area surrounding the road tend to be covered by only a relatively thin layer of soil (if any at all), held together by tree roots. The soil and water mixture adopts a consistency similar to poured concrete, and it picks up debris and sediment as it moves through a gully system that drains into the valley. In this area, Prof. Eaton said, debris can flow downslope for more than a kilometre. A debris flow typically moves about as fast as a world-record sprinter – in excess of 10 metres per second. “The bigger they are, the faster they go,” he said.

Matthias Jakob, a principal geoscientist at BGC Engineering whose PhD field work decades ago was on debris flows in the area that includes Duffey Lake Road, said that, because of their density and speed, debris flows have a very high impact force. In this case, he said, another scientific term might apply, at least at the trigger zone where the flow started: debris avalanche, for the speed at which the organic matter descended.

Charlotte Hall, who was travelling south along Duffey Lake Road with two friends late Monday morning, used the word “hurtling” to describe the rate at which trees, rocks and mud slammed onto the road during the second of the two slides that hit that stretch of the highway.

“It was immediate panic,” Ms. Hall said. “People just hopped in their cars as fast as they could to drive away from the slide. They were honking, and you could see the trees just clipping the backs of the cars.” The slide itself was over in a matter of seconds, but it pushed upward of 10 vehicles off the road and down an embankment toward a creek. Those who remained on the highway were wailing, shaking and crying.

A group of strangers got together to form a makeshift search-and-rescue crew, under the leadership of a man multiple witnesses believe was an off-duty firefighter. The group included three hunters, a forestry worker, a Commercial Vehicle Safety and Enforcement employee, and Kathie Rennie, who owns a traffic-control company. They quickly set about gathering whatever tools they could from people’s vehicles – shovels, chainsaws, tie-downs, ropes, pulleys.

The rescuers went deep into the mud trying to find cars and people. Ms. Rennie, who was appointed to first-aid duty, said the group helped four people to safety. “I assessed them and started yelling for clothes and water and socks and shoes and jackets and blankets, and people just started pulling stuff out of their cars,” she said. The rescue team, she said, never found a fifth person they knew to be missing. The man’s status remains unclear.

Ms. Rennie and the other stranded travellers got out of the disaster zone before emergency crews arrived by helicopter. A snow plow driver on the Pemberton side of the first slide managed to carve a narrow escape path through the debris. The travellers immediately convoyed out. “When that road was opened, it was go-time,” she said. “Let’s get out of here.”

At a news conference in Victoria on Monday, Mr. Farnworth was on the defensive about his government’s response to the storm. “Travel advisories and high-stream-warning advisories have been issued by the appropriate ministries over the weekend,” he said. He maintained that responsibility for flood response in communities lies with local governments. “They’re making the decisions that impact that particular community and taking the appropriate action.”

Historically, B.C.’s provincial government played a central role in managing flood risks, but in 2003 the province transferred responsibility for flood management to local governments. The offloading has resulted in a hodgepodge of regimes across the province. In Metro Vancouver alone, for example, there are 21 municipal authorities with varying capacity to deal with the growing threats of extreme weather.

There has been ample evidence in recent years that this approach isn’t working. A 2018 report by B.C.’s auditor general found that the province was ill-prepared for flooding. “The government may not be able to manage flood risks,” the report noted, “given that roles and responsibilities are spread across many agencies and levels of government, and these organizations may not have adequate staffing or technical capacity.” Most floodplain maps were outdated, it added, and the province’s dikes likely wouldn’t hold during major events. “Given the impacts of climate change,” it warned, “flood risk will likely increase in the province.”

Ms. Harper, the Emergency Management B.C. spokesperson, said the province’s new flood strategy is anticipated in mid-2022. She also said the province aims to introduce new legislation next fall that will modernize the Emergency Program Act. “This will ensure there’s adequate time to develop the legislation, considering the pause we had to take in July and August during peak wildfire activity and response,” she said.

That the government had to halt its work on emergency-management legislation because of a weather-related emergency is telling. And the situation in B.C., as elsewhere, is only going to get worse.

On the same day as the Duffey Lake Road slides, a study co-authored by Prof. Jakob, who is also an adjunct professor at the University of British Columbia, was published in the peer-reviewed journal Geomorphology. It predicts that climate change will coincide with an increase of up to 300 per cent in the frequency of landslides in Vancouver’s North Shore Mountains area by the end of this century. “Outside of the Vancouver watersheds, infrastructures will increasingly be tested by more frequent and sometimes higher magnitude landslides,” the study says.

This tested infrastructure will inevitably include dikes and highways, both of which were hard-hit this past week. The disruptions along a series of critical highways, all at once, reveal that policy-makers must change the way they think about climate-change resiliency, according to Prof. Eaton. “This wasn’t a natural disaster; this was an infrastructure disaster,” he said. “We need to really try to engage with what climate change means for our systems of infrastructure, rather than individual sites.”

In addition to emergency preparedness and infrastructure, there’s also the matter of forestry activity in the province. Whether a loss of trees is due to logging or wildfires, the effects are similar: Water and snow that would typically be intercepted by trees instead lands directly on the ground; water that would typically be absorbed by trees remains in the land; soil becomes unstable without roots to hold it together. It’s unclear whether logging contributed to the vulnerabilities in the Duffey Lake Road area.

Back in Vancouver, Mr. Tuisku is grateful to have survived the slide. He knows it was a close call – that he could have been in one of the vehicles pushed over the embankment. And he’s still shaken. “I’m waiting,” he said, fighting back tears, “until they find everyone.”