flood plain

or flood·plain


noun

a nearly flat plain along the course of a stream or river that is naturally subject to flooding.

Origin of flood plain

First recorded in 1870–75

British Dictionary definitions for floodplain

flood plain

noun

the flat area bordering a river, composed of sediment deposited during flooding

Scientific definitions for floodplain

floodplain
[ flŭdplān′ ]

Flat land bordering a river and made up of alluvium (sand, silt, and clay) deposited during floods. When a river overflows, the floodplain is covered with water.