River and Lake Boundaries

Surveying Water Boundaries - Second Edition

By James A. Simpson, PE and LS




A river’s meanders move outward and down-slope if not constrained. These movements can contribute towards formation of an avulsion in the river. An avulsion is connected with a change in river alignment which results in abandonment of all or part of a river channel.

The legal effect of avulsion is to fix the boundaries within the avulsed area as they were at the time the avulsion became complete.


Man-caused avulsions and channelization are covered as are international boundary river avulsions. Surveys and resurveys where avulsion has occurred are discussed here as well.  Litigation involving avulsions are also covered  in Chapter 7.