Meander
A river rarely flows in a straight line: it bends around because it drops sediment where it flows most slowly. There are areas of slower and faster water movement. The river flows faster on the outside of a curve, and the fast water erodes the outside bends of a river channel by hydraulic action and abrasion.  This forms a river cliff.  The river flows more slowly on the inside of the river beach.  The slower water drops sediment.