River bed
"Lowest part of a river valley shaped by the flow of water and along which most of the sediment and runoff moves in interflood periods." (United Nations Publications, 2013)
Sources
United Nations Publications. "Glossary of Shared Water Resources (English-Arabic): Technical, Socioeconomic and Legal Terminology." (2013). DOI:https://dx.doi.org/10.18356/70b462ce-en