An interlocking spur is a natural feature which occurs in a river's upper course, where downward erosion (vertically downcutting) is the dominant force in determining the river's course. As the river wanders between banks that are far apart, the promontories of the hills tend to jut out into the river valley in a staggered formation, interlocked together in a formation like the teeth of a zip. These promontories are referred to as interlocking spurs.

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