also: かせんしき
noun
riverbed area; flood plain; riverside land
Refers to the flat land along a river, often used for parks, sports fields, or agriculture, and typically within the river's flood control zone.
河川敷で野球の練習をした。
We practiced baseball on the riverside grounds.
大雨で河川敷が水没した。
The riverbed area was submerged by heavy rain.