Floods in British Columbia | When nature withdraws its rights

The men wanted to control the water, but they were able to come back. One hundred years ago there was a large lake in the Sumas agricultural plain east of Vancouver, which is now heavily affected by floods in British Columbia.

Jean-Thomas Liveill
Press

Cows up to their necks, barns submerged in water, water as far as the eye can see: The Sumas Farm in Abbotsford, east of Vancouver, looks like a large lake.

That too was a century ago.

A lake, with its area varying from season to season, year to year, about 80 km.^⁠2, Water low time, 134 km^⁠2, During flooding, extends beyond the Canada-US border.

Terence Day, a professor in the Department of Geography, Earth and Environmental Sciences at Okanagan College in Kelona, ​​said the major conflicts were causing headaches for nearby farmers.

“It was hard to fool the breeders into going up, down, and then up and down,” he says. They grazed the cattle and then had to move them as soon as the lake rose, which is why it was decided to evacuate it. ”

A diversion channel, dykes and a pumping station were built in the early 1920s, transforming this vast body of water into a fertile plain that today feeds many of Colombia’s farms, dairy and market gardens and egg production. And chicken.

Even the Trans-Canada Highway now passes through what was once Lake Sumas.

However, this work did not prevent sporadic flooding, including the most significant flooding in November 1990.

Is it a good idea to pollute the lake?

Professor Day believes it is inappropriate to ask the question from a contemporary perspective, and doubts whether such a plan would ever be implemented nowadays.

“Managing the legacy of this decision is a challenge,” he said.

Known danger … it is evolving

Although the lake has faded over time, Professor Day says living in drained land has always been a known danger.

“That’s why the pumping capacity is so high,” he says.

When operating at full speed, the four tubes could move at a rate equal to the content of the Olympic swimming pool per minute, a local newspaper explained Friday. Postford News.

But the problem is that Professor Day notes that the probabilities of flood recurrence are based on historical data that do not take into account new factors such as global warming.

“The dangers are clear [d’inondation] Will increase with global warming, but more people are living [dans la plaine de Sumas] 100 years ago, ”he says, adding to the significance of the effects of the floods.

A study conducted for the municipality of Abbotsford in 2019 recalled the risk of flooding a large flood plain and recreating Lake Sumas.

“The risks are always there, but they only get bigger over time,” says Professor Day, arguing that we need to intervene by combining long-term and short-term solutions.

In the short term, of course, we need to help people who have lost their homes and lost their source of income, but in the long run, “we need to realize and act on climate change,” he was quoted as saying. It was used in other parts of the world to expropriate some property in order to protect others and to direct direct flooding in these areas.

To flood

The great variation in the area of ​​the ancient Sumas Lake is explained by the fact that it is located in the sedimentary plain of the Fraser River, which discharges a large body of water.

“A sedimentary plain is a field where waterways migrate,” explains Maxim Bowen, a professor-researcher and geologist at the University of Quebec (UQAC) in Geographic (UQAC).

As it is by definition a place with very low variations in altitude, the river overflows and the vast expanse of land is submerged, what is currently happening in the area.

Another well-known lake once had a very different area: Lock Saint-Gene, before it was converted into a reservoir by the construction of dams.

But the terrain of the region is so different from Fraser Valley that the flooding of Lake Saint-Jean reflected, above all, a spectacular rise in its level, Maxim Bow recalled.

Thus, during the period from 1913 to 1925, the lowest level of the lake recorded during the low water period reached 86 meters, with a difference of 15 meters, compared to 101 meters during the flood period.

Professor Bowen underscores that this situation is also “very unique in the world.”