river plain; riverbed area
Refers to the flat land along a river, often within the river's floodplain or between levees. Can include the dry riverbed and adjacent low-lying areas. Used in contexts like parks, sports grounds, or land management.
A baseball field was built on the river plain.
The riverbed area was submerged by heavy rain.
Formed from 川 “river” and 敷き, the nominalized stem of 敷く “spread; occupy an area,” denoting the land occupied or covered by a river.