Breaching a dike; saving a salt marsh

In 2008, New Brunswick’s Department of Agriculture, Aquaculture and Fisheries was losing a battle with the Bay of Fundy tides. Waves were destroying the agricultural dike in Aulac, N.B., originally built to keep water in the bay’s Cumberland Basin from flooding farmland on the Tantramar Marshes.

When the department built a new dike, DUC staff approached them about forming a partnership. Their proposal: DUC would help fund the new dike, and scientific monitoring, if they could restore a salt marsh between it and the old one.

The groundbreaking project—funded jointly by the province’s Department of Transportation and Infrastructure and Canada’s Department of Fisheries and Oceans’ Small Craft Harbours program, as well as New Brunswick’s Environmental Trust Fund—would provide researchers insight into how salt marshes can help mitigate the effects of rising seas.

In fall 2010, DUC breached the old dike and allowed salt water back into two 20-acre (8-hectare) pieces of land behind it. But the dike was so weak, it eroded and opened in unplanned places sooner than expected, giving the young marsh less protection as it was establishing.

Since then, the marsh’s soil and vegetation has continued to stabilize so the marsh will be able to protect the new dike behind it. Meanwhile, researchers from DUC, nearby Mount Allison University, the University of New Brunswick and Acadia University, have discovered that plant and animal communities are becoming similar to those of other natural salt marshes near the restoration site. Thanks to this pilot project, the researchers —studying everything from birds to geomorphology—are now more prepared to undertake this kind of project in the future, and help mitigate the effects of climate change.

“It’s one adaptation to climate change, especially in low-lying areas protected by dikes,” says DUC conservation specialist Nic McLellan. “Salt marshes protect the dikes, and provide a buffer from the waves.”