beheaded stream

A captured stream is regarded as “beheaded” when its headwaters are taken over by its captor stream, which at some point broke through the physical division between the two—a natural occurrence in the ongoing dynamic process of a drainage system. The aggressor literally chops off the headwater and diverts the captured stream into its own flow, an act of stream piracy. Some misfit, or underfit, streams begin this way. Without the runoff from its headwaters, such a stream becomes too small to cut through its own valley

Gretel Ehrlich