What term describes a river's sudden change in flow to a new channel, leaving an upland area?

The term that describes a river's sudden change in flow to a new channel, leaving an upland area, is avulsion. Avulsion refers specifically to a rapid event where a river establishes a new course, often due to factors like flooding or erosion. Unlike a gradual meandering process, avulsion occurs quickly and significantly alters the landscape, which may isolate portions of land that were previously adjacent to the river.

Meandering, on the other hand, describes the slow, sinuous way a river curves across its floodplain, which does not involve a sudden channel change. A delta is a landform created at the mouth of a river where sediment build-up occurs as the river meets a body of water, such as an ocean or lake. Confluence refers to the point where two rivers meet and merge into one. These terms, while related to river systems, do not accurately describe the specific phenomenon of a river suddenly shifting its flow to a new channel.