What are waterfalls on the edge of the Piedmont called?

Waterfalls on the edge of the Piedmont are called "fall line waterfalls." The fall line is the boundary between the Piedmont and the Coastal Plain regions, where rivers and streams flow from hard, resistant rock to softer, more easily eroded rock. This change in geology creates ideal conditions for the formation of waterfalls as the water cascades over the edge of the harder rock layers.