BC storm highlights cities struggling with heavy rain

Heavy rain is not uncommon for the Deep Cove community in North Vancouver, but Ashifa Safrali knew this storm was something different when she saw an e-bike floating in the middle of the street.

Saferali owns Honey Donuts and Goodies, a fixture in the community where he has lived and worked for nearly three decades.

Flash floods have occurred in the region before, but nothing like the flood on October 19, the day of BC’s provincial elections.

“There’s a stream up the road and I don’t know if that stream was supported by leaves or debris, but it was flowing down really fast and within an hour the stream of water was gushing down. “Going down the hill,” Saferali said, “It was pretty crazy.”

By the time it was over, 350 millimeters of rain had fallen in North Vancouver, turning streets into rivers winding through waterfront homes, piling rocks and gravel, and triggering a local emergency. The district told residents of six homes on the beach that they had to evacuate.

The flood is an example of how municipal infrastructure is struggling to keep up with the demands of a rapidly changing climate as extreme events increase in frequency and worsen in severity.

Engineers who once looked to history to plan conservation measures need to look to the future, said Shahria Alam, professor of civil engineering at the University of British Columbia’s Okanagan campus.

He gave the example of municipal engineers who design a stormwater drainage system and can look at rainfall going back 50 years.

However, weather conditions are changing rapidly.

“This means that the system you designed will not be able to accommodate such a large amount of additional water, and then of course your system will fail and disaster will occur,” Alam said.

“Unfortunately, such events will continue to occur due to climate change.”

Some communities are aware of the challenges and are preparing.

The City of Vancouver says in its climate change adaptation strategy that average autumn precipitation is expected to increase by 12 percent by the 2050s.

But more concerning from an infrastructure perspective is the increasing prevalence and severity of “extreme rainfall events.” The report states that heavy rainfalls, which occurred once every 20 years between 1981 and 2010, will occur twice as frequently in the 2050s.

It is stated that during such an event, the average amount falling in a single day will increase by 20 percent to 86 millimeters.

The city says it will prepare by examining steep slopes at risk of instability and managing stormwater to better filter and store it.

But even cities that have diligently improved their infrastructure over the years may find their drainage systems inadequate.

North Vancouver District Mayor Mike Little said the city is spending millions of dollars to improve infrastructure, including the Gallant Creek watershed system in Deep Cove, which has been subject to several heavy rainfalls over the past decade.

But the October 19 storm was so severe that it paralyzed the system by clogging it with large amounts of debris.

He didn’t remember much that day watching city crews use a backhoe and remove “six to eight feet of woody debris” as they tried to clear the catch basin off steep Gallant Boulevard.

“Even though it had been cleaned out prematurely, it was coming down so far that it was still locked,” said Little, whose own basement was flooded.

Honey Donuts is on Gallant Avenue.

“You couldn’t even walk. Safrali, the owner of the facility, said, “If you crossed the street, the water would come up to your knees.”

Heather Radant, manager of the Deep Cove Collective gift shop across the street, said she got soaking wet as she fought in vain to keep out the rising waters, barricading the store with plywood, sandwich boards and sandbags provided by city staff. neighbors.

He said the scene where the store was flooded was “crazy.”

“I was thinking, ‘man, how can I stay here and try to keep the drains clean? ‘How long will the water continue to come?’ I didn’t even know,” Radant said.

More concrete infrastructure is not the ideal answer in the long term, Alam said.

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

Alam said the new rainwater processing technology, known as continuous diverter separation, can better screen out debris and sediment in running water.

But solutions can be expensive.

“I’ve seen them work hard and make improvements in many places. But not all cities have such resources, and many cities are struggling to keep up,” Alam said.

Honey Donuts in Deep Cove is experiencing activity again, there was a line out the door on a recent afternoon.

Across the street, Deep Cove Collective had reopened, thanks in part to customers and neighbors who left dehumidifiers and fans to dry out the store.

“And that’s one thing I love about being in this community, everyone comes together and helps everyone,” Saferali said.

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