As sea levels continue to rise and powerful tropical storms become more common in the region, experts say the communities straddling the Chignecto Isthmus are under increasing threat.
The Chignecto Isthmus is a narrow stretch of low-lying marshland that connects New Brunswick and Nova Scotia, protected by a series of dikes and aboiteaus constructed in the 17th century by Acadian settlers.
But those dikes, which have held back the ocean for the last few hundred years, are nearing the end of their lifespan.
“They’re made of mud and rocks and a mix of things so they were never meant to withstand something like Fiona,” said Sabine Dietz, executive director of CLIMAtlantic.
“Sackville and Amherst both have infrastructure behind the dikes. This is community infrastructure: roads, sewage, water infrastructure, there’s homes behind them, businesses behind them, Nova Scotia has the wind turbines behind them. So there’s a lot of things behind these dikes.”
The existing dikes stand at about eight metres above sea level. During high tide the powerful waters of the Bay of Fundy can reach as high as seven metres, meaning storm surge of a couple of metres could breach the dikes, with grave consequences for the low-lying areas behind them.
Portions of Sackville are five metres above sea level, the TransCanada Highway sits at about six metres and the CN rail line is around seven metres high.
Provincial flood maps say that sea level rise would cause high tide to top the dikes by the end of the century, but Dietz says a weather event like post-tropical storm Fiona would threaten the area now.
“If Fiona happened tomorrow, the dikes would not be able to withstand it,” she said. “You’d have water everywhere, you’d have damage of infrastructure.
“If you have five centimetres of water over a road, if it’s not moving too much, that’s OK, infrastructure can handle it. If you get three metres of water over a road, you’re looking at washouts, you’d be very quickly looking at damage to infrastructure.”
A proposal to raise or replace the dikes is being discussed, which carries a price tag ranging between $200 and $300 million and a 10-year timeline. The federal government is offering to pay for half the project, but that offer isn’t quite good enough for provincial governments in Nova Scotia and New Brunswick.
New Brunswick Infrastructure Minister Jeff Carr told the legislature’s estimates committee in April that the province feels Ottawa should take on the “lion’s share” of the cost for the project since it would primarily protect federal infrastructure like the highway and rail line.
“The behind-scenes work is happening between the two provincial governments on governance structures and those pieces like that, we just need the federal government to be at the table in a more substantial way,” he said.
“We appreciate their generous offer, we really do … but we feel the federal government needs to take a more important role.”
But some have criticized the proposal, saying a more complete and nuanced solution is needed. Jeff Ollerhead, a coastal geomorphologist at Mount Allison University in Sackville, says more options need to be considered.
“You need to work with communities to come up with a strategic, holistic plan for how you’re going to deal with the landscape and simply putting the dikes back where they currently are … it’ll be an ever-growing cost to society to maintain them where they are because they will become increasingly out of equilibrium with the system,” he said.
Ollerhead says the best solution would likely include a mix of bolstering dikes, resettlement and restoration of the natural salt marshes.
While it would likely cost more up front, he says it could be cheaper in the long term considering the money required for maintenance if the current proposal goes ahead. He added that the salt marshes would also act as a massive carbon sink and could be used to generate revenue in the future should a global carbon credit trading system ever be established.
“I don’t think the focus should be on the capital cost. It may not even matter if it costs $400 million to put a solution in if that solution would decline in operating cost as time goes on … it would be a better solution,” Ollerhead said.
“We should figure out what it actually costs all in over 50 years and not focus just on the capital cost over four years or five years, or however long this will take.”
As various levels of government haggle over the cost, there’s a growing sense of urgency in Sackville that something needs to move forward. Andrew Black, the mayor of Tantramar, says he’s been hearing about possible solutions to protect the isthmus since 2016, but little progress has been made over the last six years.
“The concern is great in the community and I think that it would be great if it got started, some commitment to at least start the project, whichever one it was going to be, because it’s going to be a 10-year project,” he said.
“As each passes, the possibility of a Fiona-level storm or the storm we had in 2015 could happen again.”
The town of Sackville, which is now part of Tantramar, has spent about $15 million over the last number of years to establish storm ponds to help deal with inland flooding in the town’s low-lying areas. That infrastructure would be under threat if the dikes breached. Black is hoping the various government involved can begin work to ensure the area is better protected from coastal flooding too.
Black says he understands the price tag for the dike project is high, but says the consequences of a dike breach would be catastrophic and have impacts throughout the country.
“The sort of back and forth between the provincial and federal government about who’s going to foot the bill is frustrating,” he said.
“It’s not a small bill but … we know that $35 billion a year goes across that strip of land by rail and by road, so $300 million if that’s what it would cost is a drop in the ocean compared to the amount of money that would be lost even if that piece of land was flooded for a couple weeks.”
And while he says the project is no “silver bullet,” recognizing that more will need to be done to mitigate and adapt to the growing risks, Black says it’s time that something is done.
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