Meander scar

They are characterized by "a crescentic cut in a bluff or valley wall, produced by...a meandering stream.

[5][6][7] The term itself may refer alternatively to the actual cuts into the bank of a bluff,[1] or to the general feature of a drying or dried meander.

Meander scars are caused by the varying velocities of current within the river channel.

Due to higher velocity current on the outer banks of the river through the bend, more erosion occurs causing the characteristic steep outer slopes.

[1] In certain habitats, if the scar has sufficient water, or as an oxbow lake fills with sediment, these areas may become marshes or wetlands.