Champaign and Flood plain

Champaign noun - A broad area of level or rolling treeless country.

Flood plain and champaign are semantically related. In some cases you can replace phrase "Flood plain" with "Champaign", this terms are similar.

Flood plain noun - A low plain adjacent to a river that is formed chiefly of river sediment and is subject to flooding.

Champaign and flood plain are semantically related. Sometimes you can use "Champaign" instead a noun phrase "Flood plain".