‘Parade of storms’ How did heavy rain become so disastrous in British Columbia?

What has happened?

A huge storm dumped record rainfall across swathes of British Columbia in Canada and Washington state in the US between 13 and 15 November.

Thousands of people have been forced to leave their homes, others became trapped on impassable roads, and several towns were completely cut off. Mud and landslides have destroyed sections of highways. British Columbia’s premier declared a state of emergency last Wednesday and troops were deployed to help those still stranded.

The port of Vancouver, the largest in Canada, was forced to suspend all rail access, and the city was all but cut off from the rest of Canada. At least four people have been confirmed dead with others missing.

In the town of Abbotsford, farmers ignored an evacuation order to try to save their animals from rising waters, some tying ropes around the necks of cows and pulling them to higher ground.

Why was the flooding so bad?

The area has been drenched by unusually heavy rain – what one meteorologist has referred to as a “parade of storms” – since September. More rain fell in Bellingham in Washington state between Saturday and Monday than is usual for all of November.

The heavy rainfall is linked to an atmospheric river. Hurricane scientist Jeff Masters has described the phenomenon as like “a pipe

transporting huge amounts of water vapour out of the tropics”.

The flooding has been exacerbated by clearcut logging and the rate at which water is absorbed into the ground and the ability of root systems to hold water and stabilise soil. Without trees, heavy rains can wash large amounts of earth into nearby water systems, choking creeks and streams and causing them to quickly overflow.

The risk of landslides has also been heightened by summer wildfires. “There’s a very clear link,” Thomas Martin, a forester in the province, said. “There are fewer living things to intercept the water. It just flows directly off the hill. And fires can make the soil hydrophobic so the runoff increases.”

What happened in the summer?

The storm hit the same region that five months ago suffered an extreme heatwave, fuelling destructive wildfires. In June, the mountain town of Lytton registered 49.6C, crushing Canada’s record.

Police stations and hospitals reported a surge in heat-related deaths – 486 in British Columbia, and dozens more south of the border. Roads buckled as asphalt expanded. At least one city had power cuts. The extreme weather was caused by a “heat dome” created when high pressure in the upper atmosphere acts as lid, preventing hot air from escaping.

How is the situation linked to the climate crisis?

Scientists who analysed the heatwave found that human-caused climate change made the extreme weather at least 150 times more likely to occur. water treatment systems to fail, and the local government has warned residents not to drink tap water even if they boil it first.

While Merritt did not experience flames during the summer fires, Bhangu said his residents had suffered from thick smoke and extreme heat that reached 44.5C at the height of the heatwave. There were tense times when the town was put on evacuation alert, and people were worried they could lose their homes to the fires. The floods came when many were still struggling with the emotional aftermath of the summer’s blazes.

“I don’t think we’ve had an opportunity to process the fire season,” said Bhangu, who evacuated to a nearby city after floodwater swept through his town. “It takes some time after an event to grasp what you just went through and people didn’t have an opportunity to do that. It’s emotional, it’s stressful.”

The impact of the torrential rain has been widespread. Vancouver, which sits in a valley that funnels into mountainous terrain, has effectively been cut off from the rest of Canada, with road access only possible by a detour through the United States. Local media reported panic buying that left produce aisles empty, and the provincial government has been limiting sales of petrol in areas near the landslides after the storm damaged a gas pipeline.

Back in Lytton, Thorpe said the sense of community is what made her want to stay in the town, despite the terrible events over the past year. Volunteers in the community had come together to clean her property and build a new house in the aftermath of this summer’s fires, and she said the community will get through these floods together too.

“The people have been so resilient. This is where we belong, they’re family,” she said.