A fifteen-foot-tall turf-covered earthwork berm, it happens to be identical in height and construction to the original westernmost portion of Hadrian’s Wall.

It’s especially refreshing to see Ms. Buchanan’s 1981 earthwork “Marsh Ruins,” for instance, as conversant with Robert Smithson’s similarly diffuse, ephemeral land art.

The group called Earthworks has commissioned an assessment of the potential risks to the local waters.