B.C. atmospheric river a successful first test of community-led rain management project

The St. George Rainway runs along East Vancouver’s St. George Street

Isaac Phan Nay, CBC News. October 26, 2024. Original article.

The torrential rains that drenched the Lower Mainland last weekend were the first test for a new, community-led rainwater solution in Vancouver’s Mount Pleasant neighbourhood. 

The St. George Rainway, which is still under construction, is a City of Vancouver project designed at the request of the community and with its input. It includes pebbles, soil and vegetation running along the east side of St. George Street as it slopes from East Broadway Avenue to East Fifth Avenue.

It follows the path of an ancient, buried creek and soaks up rainfall that would otherwise pool up and flow down the street. When torrential rains reached the Lower Mainland last weekend, causing damage and mudslides across Metro Vancouver, the unfinished rainway helped keep the street from flooding. 

When it’s done, the four-block project will be able to drain 17,000 cubic metres of water per year from the roadway — as much water as approximately seven Olympic-sized swimming pools. 

Meanwhile, a city engineer and a flood researcher say projects like St. George Rainway could be a key way to protect neighbourhoods across Canada from heavy rainfall. 

The road and homes along St. George Street are constructed above a creek that historically emptied into False Creek. The creek still runs underground, through a series of pipes and culverts — where it hasn’t offered the community adequate drainage for at least a decade, often leading to street flooding and damage to the roadway.

Rita Wong, a local resident, said rain would cause massive amounts of water to pour down St. George Street, often seeping into her neighbours’ basements. Flooding on the street had contributed to cracks and potholes that marred the asphalt.

“When it rained heavily, you could see where the river used to be because the flow of water was still up on the street,” she said. “There was just a lot of water coming down the street, and it had nowhere to stop.”

Wong said she had heard of other buried creeks across the city being uncovered to restore the ecosystems’ natural drainage systems.

In the early 2010s, Wong and her neighbours held a series of meetings about the flooding. Together, they asked the city to find a way to restore the creek — a plan that would eventually shape the St. George Rainway.

But according to Robb Lukes, the city’s associate director of green infrastructure implementation, uncovering the creek would mean moving several homes and rerouting a gas line. 

“Doing a full stream [surfacing]  wasn’t going to be practical. It’s a very deep stream,” Lukes said. “But what we could do is this rainway, which is a representation of that historic stream.”

Instead of uncovering the creek, the city built a blocks-long garden that would mimic the creek. 

The project cost $6.2 million, 60 per cent of it funded through an Infrastructure Canada grant called the Natural Infrastructure Fund. 

The project got underway in 2023, but construction started in earnest this summer. 

The street was narrowed to make room for the rain garden. By the start of this month, the channel along St. George Street was peppered with grasses, trees and pebbles. 

Every metre or so, a barricade called a weir slows — but doesn’t stop — the flow of water through the rain garden. Some blocks have benches or chairs built into the channel. 

Lukes said the project will help prevent flooding in the neighbourhood as it experiences stronger rainfalls. 

“It filters runoff, absorbing it, keeping it out of the sewer system and helping to maintain [drainage] capacity, as we experience more intense rain events from climate change,” Lukes said.

The project is the city’s largest rain garden. He said the solution would scale well along the city’s bikeway corridors, where pedestrian and cyclist safety is a priority.

Already across the city, there are about 300 similar rainwater projects, including the covered, tree-lined trenches that filter rainwater off Richards Street downtown — a solution Lukes said works in busier environments, like along the Broadway Subway extension. 

The rainway faced its first test last weekend when an atmospheric river soaked the Lower Mainland.

Environment Canada data shows rainfall records were set across Metro Vancouver. According to the city, anywhere up to 211 millimetres fell on Vancouver proper. 

On St. George Street, rain soaked into the soil and the vegetation. Water flowed down the rainway like a creek, instead of pooling on the street. 

“It performed beautifully,” Lukes said. “We were able to see all of the weirs in action and the flow along the rainway.”

Loree Campbell, who has lived on the street for more than 15 years, said she watched the rainway in action Sunday. 

“It worked perfectly. It was really beautiful,” she said.

The other half of the project, which will close St. George Street between Sixth and Seventh avenues to cars to extend the garden down the road, is scheduled to be completed in December. 

Campbell, who has joined the community in asking for the rainway, said she’s looking forward to having it completed. 

“It’s just absolutely gorgeous,” she said. 

Charlotte Milne, a flood risk researcher at the University of British Columbia, said projects like the rainway can help Vancouver manage rainfall as atmospheric rivers become more extreme.

“It’s not just nuisance flooding that we’re seeing. It’s pretty regular flooding that’s going to increase into the future,” She said. “Wider implementation of these projects would help a lot.”

She said infrastructure like rain gardens are often less expensive than traditional stormwater systems and provide greenery. 

They are not perfect for every situation, she said, adding they might not be a realistic solution for busier areas, roads where there isn’t enough space to accommodate necessary traffic, or where residents resist the changes.

Milne said they may not be able to handle the extreme amounts of rainfall that are more likely to occur with climate change. 

Still, she said incorporating vegetation and water flow into city infrastructure will help cities cope with rainfall better than ditches, sewers and culverts. 

“We’ve definitely got some issues with our stormwater systems, but a better solution is to keep implementing these natural ones throughout the city,” Milne said. “They can have a greater benefit in the long term.”