Chignecto Isthmus communities under increasing threat of coastal flooding: experts

Experts say a powerful storm could breach the dikes that protect the Chignecto Isthmus, which would damage some communities in the region.

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.