noun
river delta
Geographical term for a triangular landform at a river mouth formed by sediment deposition.
ナイル川の三角州は広大な農業地帯です。
The Nile River delta is a vast agricultural region.
地図で三角州の形を確認した。
I checked the shape of the delta on the map.
Compound of 三角 (triangle) and 州 (sandbank, delta). The spelling 三角洲 uses 洲, a variant character also meaning sandbank or islet.