Relatively flat land that borders a river channel and defined by the high water mark reached during flooding. Low gradient rivers tend to have a meandering form which makes the floodplain very wide because previous channels would have been in positions other than the current one. Because the area receives new sediments during floods, floodplains tend to be very fertile. The bottom photograph shows a floodplain of the Owens River in California. Some of the old river channels can still be seen.

After "Earth, An Introduction to Physical Geography"