A ridge of sand, rock, and other debris can be found running along the back of most beaches. This berm—the term can also include the flat behind the ridge—marks the spot reached by the swash of water from the highest wave of the worst storm; it will stand witness until some higher wave eventually scours farther up the shore. A series of smaller berms mark successively lower high-water marks, right down to the line of seaweed along yesterday’s high tide line—each more ephemeral than the last. The term has slowly acquired more meanings: in the nineteenth century, it was the bank of a canal opposite the towpath; in our time, it is the raised shoulder at the side of a road.

Bill McKibben