British Columbia storm highlights cities’ struggle with heavy rain

Heavy rain is nothing unusual in the Deep Cove area of ​​North Vancouver, but when Ashifa Saferali saw an e-bike floating in the middle of the street, she knew this storm was something else.

Saferaly is the owner of Honey Donuts and Goodies, an establishment in the community where she has lived and worked for nearly three decades.

She has dealt with flash floods in the area before, but this is nothing like the deluge on Oct. 19, the day of the provincial election in British Columbia.

“There’s a creek up the road from us, and I don’t know if the creek was clogged with leaves or debris, but it was coming really fast, and within an hour the water just came pouring down. hill and go straight down,” Saferali said. “It was pretty crazy.”

By the time it was over, North Vancouver had received 350 millimeters of rain, turning streets into rivers that flowed through waterfront homes, accumulating boulders and gravel and triggering a local state of emergency. The county told residents of six homes along the riverfront that they needed to evacuate.

The flood is an example of municipal infrastructure struggling to cope with the demands of a rapidly changing climate as the frequency of extreme events increases and their severity worsens.

Engineers who once looked to history to plan safety measures must instead look to the future, says Shahriya Alam, a civil engineering professor at the University of British Columbia’s Okanagan campus.

He gave the example of municipal engineers designing a storm drain system who might look at 50 years of rainfall.

But weather conditions change quickly.

“What this means is that the system you designed won’t be able to accommodate that huge amount of extra water, and then of course your system will fail and there will be a disaster,” Alam said.

“Unfortunately, incidents like this will continue due to climate change.”

Some communities are recognizing the challenges and are preparing for them.

The City of Vancouver, in its climate change adaptation strategy, says average fall precipitation is expected to increase by 12 per cent by the 2050s.

But of even greater concern from an infrastructure perspective is the increasing prevalence and severity of “extreme rain events.” It says precipitation so heavy that it occurred only once every 20 years, from 1981 to 2010, will occur twice as often by the 2050s.

The average amount lost per day during such an event will increase by 20 percent to 86 millimeters, the report said.

City officials say they will prepare by studying steep slopes that are at risk of instability and managing rainwater to better filter and store it.

But even cities that have diligently upgraded their infrastructure over the years can find their drainage systems overloaded.

District of North Vancouver Mayor Mike Little said the city has spent millions upgrading infrastructure, including the Gallant Creek watershed system in Deep Cove, which has seen a lot of heavy rainfall over the past decade.

But the October 19 storm was so strong that it paralyzed the system, filling it with massive amounts of debris.

Little recalled city crews using a backhoe that day to try to clear a catch basin on steep Gallant Avenue, pulling out “six to eight feet of wood debris.”

“Even though it had been cleared out beforehand, there was so much falling down there that it was still locked,” said Little, whose own basement was flooded.

Honey Donuts is located on Gallant Avenue.

“You couldn’t even walk. If you crossed the road, the water would be up to your knees,” said owner Saferali.

Heather Radant, manager of the Deep Cove Collective gift shop across the street, said she was left soaking wet as she fought in vain against the rising water, barricading the store with plywood, sandwich boards and sandbags provided by the city and neighbors.

She said the store flooding scene was “wild”.

“I was like, man, how can I just stay here and keep trying to clear the drain? How long will the water last? I didn’t even know,” Radant said.

Alam said the ideal long-term answer is not more concrete infrastructure.

Instead, he pointed to “climate resilient” solutions such as rainwater harvesting and installing “green roofs” on buildings covered with plants and soil to store and retain moisture.

A new stormwater treatment technology known as continuous diversion separation can better separate trash and sediment from wastewater, Alam said.

But the solutions can be expensive.

“I have seen in many places how they are working hard and making upgrades. But not all cities have such resources, and many cities are struggling to keep up,” Alam said.

Back in Deep Cove, Honey Donuts is bustling again, with a line out the door on a recent afternoon.

The Deep Cove Collective store across the street has reopened, thanks in part to customers and neighbors who brought dehumidifiers and fans into the store to help dry out the store.

“And that’s what I love about this community—everyone comes together and helps everyone,” Saferali said.

This report by The Canadian Press was first published Nov. 2, 2024.