What Is The Imaginary Line Between The Piedmont And The Coastal Plain Where Rivers Rapidly Descend?

What Is The Imaginary Line Between The Piedmont And The Coastal Plain Where Rivers Rapidly Descend? A fall line is the imaginary line between two parallel rivers, at the point where rivers plunge, or fall, at roughly the same elevation. Fall lines are often located where different elevation regions, such as coastal and piedmont, meet.