What is a head cut in stream terminology?

In stream terminology, a head cut refers to an abrupt vertical drop in the stream channel, often occurring where a stream encounters a more resistant material or where erosion has taken place. Over time, the head cut can migrate upstream, leading to significant changes in the stream's topography and ecosystem. This phenomenon often indicates active erosion processes and can contribute to the deepening and widening of the stream channel. Understanding head cuts is essential for managing stream health, as they can impact sediment transport and aquatic habitats. Other definitions provided in the options refer to different aspects of stream morphology and ecology, but they do not accurately capture the specific nature of a head cut as an erosive feature within a stream channel.