A major washout has halted traffic along part of Canadian National Railway Co.'s main line in Nova Scotia after torrential rain and flooding struck the province over the weekend.

The disruption threatens to constrict the flow of container goods from Halifax to Montreal, Toronto and Chicago only days after service resumed across the country at B.C. ports, and raises alarming questions about infrastructure stability amid growing climate volatility.

The heavy rains washed out a culvert that left a stretch of track sagging unsupported over a massive ditch some 90 kilometres north of Halifax on the key rail connection for freight and passengers between the city and the rest of the country.

"Over the weekend, our network in the area was impacted by washouts, flooding and power outages. CN crews have already restored much of the damaged infrastructure, but some repairs will be delayed until the floodwaters recede," CN spokesman Scott Brown said in a statement.

"As of Monday morning, all CN tracks are passable in Nova Scotia except for a significant washout that occurred just south of Truro."

Canada's biggest railway declined to offer an estimate as to when service on the now-unmoored track would resume.

Via Rail has also issued a travel warning after three months' worth of rain deluged the province in 24 hours.

"As such, Via Rail's ocean route between Montreal and Halifax cannot operate east of Moncton, N.B., until further notice. No alternative transportation will be provided and impacted passengers are being contacted directly to inform them of the situation," spokesman Karl Helou said in a statement.

Those scheduled to board on that stretch of track — two stops lie between Halifax and Moncton — can receive a full refund if they opt to cancel or can change their ticket without charge, he said.

No new bookings are available until Friday between Halifax and Moncton, which sits about 260 kilometres northwest of the Nova Scotia capital.

The provincial state of emergency declared by the government Saturday is set to remain in effect until Aug. 5. On Sunday, federal Emergency Preparedness Minister Bill Blair approved a request from the province for continued assistance.

A severed rail artery could send ripples through the wholesale and retail markets of Canada and the upper United States, said Jacques Roy, professor of transport management at HEC Montreal business school.

"It's quite critical for any freight coming from the Port of Halifax that has to be moved inside Canada or even to the U.S.," he said, noting that no other large railway serves the port.

"The shippers and importers really depend a lot on this link. The alternative, of course, would be to use trucks, but you can imagine the cost of moving containers by truck from Halifax to Montreal and Toronto."

Last year, the Port of Halifax handled more than 600,000 20-foot equivalent units, or TEUs, last year (a TEU is the measurement of a standard 20-foot shipping container). Carrying products ranging from kitchenware to construction materials, the containers add up to 11,500 per week, most bound for the North American interior.

Experts say billions of dollars more are needed to strengthen road and rail networks against extreme weather — poised to strike with greater frequency amid global heating — such as the nearly 900 wildfires raging across the country as of last week or the atmospheric rivers that washed out transport links in British Columbia in 2021. 

Vital road, rail and port connections were cut for weeks when a series of record-breaking rains drenched southern B.C. in November of that year, flooding highways and farms and forcing about 15,000 people to evacuate their homes.

"The next question is, what do we do about it? In some cases, you could have alternate routes," Roy said. "But that's not always the case."

Government and major companies should conduct risk analyses to foresee where problems could arise and shore up infrastructure and contingency plans where possible, he said.

In October, a federal supply chain task force released a final report with 21 recommendations to improve Canada's supply chain, including to invest more in infrastructure around locations "most vulnerable to climate-related or other natural disasters."

Those projects could include alternate routes as well as "supply chain crisis working groups" in each province and territory to cope with "climate shocks" such as floods and wildfires.

"Extreme weather events are happening more frequently, further increasing the risk of disruptions to the transportation supply chain — and the corresponding financial and economic impacts across Canada," the report stated.

In 2021, severe weather caused $2.1 billion in insured damages, which does not include costs related to public infrastructure or uninsured private losses, according to the Insurance Bureau of Canada. In 2022 that rose to $3.1 billion.

Canada's new national climate adaptation strategy, rolled out last month, will tie future federal infrastructure transfers to the provinces to projects that incorporate adaptation efforts.

Blair Feltmate, head of the Intact Centre on Climate Adaptation at the University of Waterloo, has said the strategy rightly lists fires, floods and heat as the biggest risks, noting the first two are the most costly and the third the most deadly.

But he has also highlighted fears the government won't follow through, and pointed out adaptation plans and promises made in both 2016 and 2018 went nowhere.

The 2022 federal budget committed $603 million over five years to support transportation network upgrades such as port or rail expansions, on top of the $4.3 billion allocated to the National Trade Corridors Fund since 2017.

This report by The Canadian Press was first published July 24, 2023.