Why is the flooding in Abbotsford so severe? A look at the Nooksack

Water spilling across the Canada-U.S. border from the Nooksack River is contributing to the massive flooding in Abbotsford this week.

According to Dave Campbell at the BC River Forecast Centre, the whole area is an extension of the same floodplain left behind by the glaciers, meaning there’s not much separating the watersheds.

“Really the Nooksack is kind of flowing along that old floodplain, so it’s a lot of close connection between the flows that come out of the Nooksack up into the watersheds on the Canadian side,” he explained.

“The floodplain itself, the area is very flat so it’s a very narrowly defined watershed boundary between what flows into the Sumas River on one side and the Nooksack River on the other side. Normally it’s fine, the rivers are contained within their banks and there isn’t an issue, but when we get these flood conditions, the water spills out of the Nooksack River and can cross that divide, which is quite low.”

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The kind of flooding we’re seeing in the Abbotsford area is “incredibly unusual,” Campbell notes, describing the current situation as a “significant event.”

However, this kind of thing has happened before.

“There was a significant event in 1990 that was very similar to this,” he told CityNews. “I think it’s a little preliminary for us to sort of get the handle on whether this is worse or not.”

Because of how flat the land is in the region, it will likely take a while for all the floodwater to drain off.

The speed and sheer persistence is this river is astonishing.

Homes in the area below the level of the levee are sandbagging, just in case. pic.twitter.com/hy7xthtFsk

— Peter Wagner (@peterjontheair) November 16, 2021

When it comes to current water levels, Campbell admits it’s a little more complicated than just about the spillover. Drainage features, protection works, flow, and terrain, are all factors currently at play and that can impact how quickly water can rise or fall.

“I think a lot of us are looking at this event and trying to piece together. We’re still very much in the response phase of things,” Campbell said. “I’m sure there will be a lot more digesting of the specifics of the event and the implications as we go forward for things like climate change.”

He notes we are expecting to see extreme weather events become more severe and frequent in the coming years, admitting this latest storm and subsequent flooding is likely not going to be the worst we’ll see.

There’s also been a lot of chatter about the former Sumas Lake, which used to sit where the current Sumas Prairie is located.

The lake was drained in the 1920s, giving way to land that is mostly used for farming today.

-With files from Lasia Kretzel