A scientist at Mount Allison says he’s disappointed that a $700,000 study has recommended raising dykes to protect the Chignecto Isthmus from flooding without including any nature-based solutions.
“It’s a little disheartening to think that we’re going to use 20th century solutions for a 21st century problem,” says Professor Jeff Ollerhead who teaches in the university’s department of geography and environment.
“There are other creative ways with multiple benefits that can be employed for the 21st century,” he adds.
He was referring to an engineering report released last week that recommends spending $190 to 300 million to raise dykes to 10.6 metres to protect the TransCanada Highway, the CN Rail line and other critical infrastructure on the isthmus.
Ollerhead himself has been working for 10 years on the Aulac salt marsh restoration project in front of Fort Beauséjour.
He explains that after the province moved a badly eroding dyke about 70 metres inland, he and his colleagues created a plan to let sea water flow into the space between the old and new dykes turning it into salt marsh.
“A salt marsh will grow naturally, vertically with rising sea level, at least in the upper Bay of Fundy,” Ollerhead says.
“There’s plenty of sediment available for that to happen,” he adds.
‘The vegetation will provide natural protection to the dykes, buffer wave energy and so, you basically get a natural buffer, natural protection at no ongoing maintenance cost.”
Ollerhead explains that for natural protection to work effectively, some existing dykes would need to be moved inland and there’s plenty of room for that in most places without affecting either the highway or rail line.
“So let’s say you wanted to move a dyke back 300 metres and create salt marsh out in front of it as a natural buffer,” he says.
“Well, obviously that 300 metres of land, somebody in most cases either owns that land or uses it, so you would have to engage [negotiate] with those stakeholders,” he adds.
Protect every inch
Ollerhead says the engineers who conducted the study seemed to start from the assumption that every inch of land must be protected by existing dykes without taking into account the benefits of a natural buffer that would also sequester carbon linked to climate change.
“Nobody’s saying that there’s no need to raise and reinforce some of the dykes,” he says.
“All people are saying is there are other solutions that can be employed that are more environmentally friendly and more cost-effective over the long term,” he adds.
“If you look at Europe, for example, where they’re doing some of these projects, where the land would be on a dollar-for-dollar basis worth far more, they’re doing exactly this, moving dykes back in some cases 300-400 metres in order to create natural habitat and get ready for climate change.”
He says that selling carbon credits could generate revenues to compensate landowners.
Ollerhead is particularly concerned that two of three options in the engineering study call for construction of a water control structure where the Tantramar River drains into the bay.
Although provincial officials say the big water gates would be closed only when exceptionally high tides threaten extensive flooding, Ollerhead points out that no studies have been conducted on potential effects.
“Nobody’s done the [scientific] modelling work on whether this could actually be done in a way that wouldn’t be disruptive to the wider eco-system.”
He says he finds it perplexing that the causeway and water control structure were removed with much fanfare from the Petitcodiac River in Moncton, and yet a big control structure is now proposed for the Tantramar River.
“Have we learned nothing from the Petitcodiac?” he asks.