BC has been warned for years with the potential for the failure of the central Sumas dike

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Dikes that were breached in Abbotsford this week after a massive rainstorm were predicted to fail years ago.

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In fact, a consultant report found that most of the sample of dikes surveyed in the lower mainland were vulnerable to error.

The faults in a 100-meter section and another, smaller section at Cole Road, of the Sumas Lake extraction dike in Abbotsford have exacerbated the floods of the 150,000-acre community in Fraser Valley.

A temporary replacement is being built instead of 100 meters of failure to prevent more water from flowing into Sumas Prairie, an area of ​​farms with a population of about 3,000. Lake Sumas was drained in the 1920s to create much of the farmland.

John Clague, professor emeritus of geosciences at Simon Fraser University and a longtime supporter of swift action against climate change, said a legitimate question is why such information has not been followed.

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“What’s the point of putting it together if you do not have to do anything?” asked Clague.

The 2015 study by the government of BC consultants assessed a sample of 75 dikes on the lower mainland and found that 71 per cent were vulnerable to failure at overtop, where floods go over the top of the dike and wash it away, either during a major Fraser River or coastal flood.

The report rated the highest elevation of the central Sumas Lake extraction dike in Abbotsford as “unacceptable”, the lowest possible in the study. “Overcrowding is expected during the Nooksack River overflow,” the report said.

And that’s exactly what happened this week.

The report noted that the height of the dike at the Cole Road junction was 60 centimeters below the design for a major flood. The dike collapsed at the site this week.

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Provincial and local officials have been aware of the risk of dike failure and a major overflow of the Nooksack River for years.

But action that comes at a high dollar price has been slow.

In a briefing Friday, Secretary of Public Safety Mike Farnworth said there have been continued maintenance and dike improvement projects.

“But you know, events like this show very clearly that climate change will affect us in ways they never did before,” Farnworth said. “That means yes, the province and the federal government are going to pay and invest in our dike system in the years to come,” he said.

Following the 1990 flood of Nooksack, which caused extensive flooding in Abbotsford, an international group was set up to assess risks and come up with a mitigation plan. The Nooksack River International Task Force was active until 2012, then went into hibernation for eight years before being revived in May 2020.

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Originally, it included members of the BC, federal and Abbotsford governments, as well as representatives of federal, state, county, and community governments across the border.

The new iteration of the task force has the same types of members, but fewer participants from the United States

As early as 2003, the task force had warned that a 200-year flood would submerge Highway 1 for nine days and flood 1,160 primarily agricultural properties with a conservative $ 130 million damage estimate.

An updated 2020 consultant report conducted for the city of Abbotsford found that the damage from a major flood could be as high as $ 960 million.

Early estimates this week for dike repairs and flood compensation in Abbotsford alone top 1 billion.

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Dike corrections outlined in the 2020 report can cost anywhere from $ 29 million to $ 339 million, but no action has been taken.

When the report was delivered, Abbotsford city councilors said finding a solution to the risk of flooding and getting funding from higher levels of government is a problem that should not be dropped or shelved.

Repair work is underway on the larger of two quarries in the Sumas Lake extraction dike at Abbotsford near No.  4 Road and Trans Canada Highway.
Repair work is underway on the larger of two quarries in the Sumas Lake extraction dike at Abbotsford near No. 4 Road and Trans Canada Highway. Photo by JENNIFER GAUTHIER /REUTERS

Last December, Mayor Henry Braun said risks associated with inadequate dikes and overflow problems from the Nooksack River were already known. He noted that the amount of money required to reduce risks is not easy for seniors at government level to contend with, including probably in the United States.

“We have to keep up the pressure,” Braun said.

Abbotsford City Councilor Brenda Falk said at the time that it is easy to forget the risk of flooding until you have a flood.

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“So this is a very big eye opener,” she said, talking about the report. “I’m sure for some who do not even realize that we have such a danger here in our region, and the work is very important.”

The 2020 report noted that options considered to mitigate flooding from the overflow of the Nooksack River into the Sumas Prairie area had included raising the dikes.

Postmedia has learned that the province has carried out an updated risk assessment of the more than 200 regulated dikes in BC, with a total length of over 1,100 kilometers. It was completed in February 2021.

But officials say that due to the size and scope of producing the provincial-wide dike review, the data has taken some time to compile and visualize.

Officials said the ministry is in the process of completing quality control and intends to deliver the results through a “secured dike information portal” to local governments and other dike authorities when it is completed next month.

ghoekstra@postmedia.com

twitter.com/gordon_hoekstra

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