Erosion along the shoreline at the Fortress of Louisbourg in Cape Breton. (CBC)

A storm surge that hit Nova Scotia in early January damaged more than the coastline of Cape Breton — it washed away 18th-century artifacts and took a bite out of a gravesite at the Fortress of Louisbourg.

The national historic site is a reconstruction of about a quarter of the town built by the French beginning in 1713. The rest of the site, the largest reconstructed 18th-century French fortified town in North America, is still under the ground, much of it next to the Atlantic shoreline.

The storm surge — high winds combined with high tides — happened during a winter storm Jan. 2.

The surge washed away a part of the fortress's history, said Willis Stevens, the cultural resource manager.

"Foundations, fortifications, the curtain walls — you'll also find remnants of the social life, the military, all sorts of artifacts that are representative of the 18th century," Stevens said Wednesday.

The high water also ate into a mass gravesite first uncovered by a storm surge in 2006 and destroyed the fortress's seawall gate.

"This is a pretty substantial gate we have here," Stevens said. "The gate was torn off its hinges, basically destroyed, and moved further up the coastline."

Fortress spokeswoman Germain LeMoine said staff are working with experts on the coastal erosion that is taking a toll on the site.

They will try to recover the lost artifacts "and do what we have to do with those archeological finds so that we can preserve them for the future," she said.

The February 2006 storm surge washed away parts of the coastline at Louisbourg, revealing a 250-year-old defence wall long thought destroyed.

Besides revealing the burial plot, it also uncovered a house foundation and a soldier's outpost, all of great historical significance.