noun
Refers to a constructed channel or trench for carrying off water, such as a roadside gutter or a drainage ditch.
道路の排水溝が詰まっている。
The roadside gutter is clogged.
大雨で排水溝から水があふれた
Water overflowed from the drainage ditch due to heavy rain.
側溝 is a roadside ditch or gutter, often synonymous with 排水溝, but 排水溝 can be used more broadly for any drainage channel.
Compound of 排水 (drainage) + 溝 (ditch, gutter).