A drainage channel or gutter (a ditch or trench) used to carry away water such as rain or excess runoff.
大雨のあと、近所の排水溝があふれて道路が冠水した。
After the heavy rain, the neighborhood drain overflowed and the road flooded.
落ち葉が排水溝に詰まって水が流れない。
Leaves are clogging the gutter, so the water won't flow.
工事で道路の排水溝を深くして排水性能を向上させた。
The road's drainage channel was deepened in the construction to improve drainage performance.