A revetment, or facing, protects an embankment against erosion. Revetment materials range from stone, concrete, and mixed rubble to dead trees and specialty fabrics known as revetment mattresses. Shoreline revetments may be used to check erosion on lakes and along coastlines. Stream revetments, also called riprap revetments, stabilize banks by reducing slumping and deﬂecting the channel away from the bank or slowing the stream’s velocity against it. On small streams, tree revetments—cut trees laid against the bank—offer a biological alternative to the once common D-Day–style rubble pile of broken concrete.