river channel; floodway
Refers to the physical channel or course of a river, often in engineering or geographical contexts.
この地域の河道は大雨で氾濫しやすい。
The river channel in this area is prone to flooding during heavy rain.
河道の改修工事が来月から始まる。
River channel improvement work will start next month.
natural damming of a river
Compound of 河 (river) and 道 (path, way), literally 'river path'.