Street gutter

A street gutter is a depression running parallel to a road designed to collect rainwater flowing along the street and divert it into a storm drain. A gutter alleviates water buildup on a street, allowing pedestrians to pass without walking through puddles and reducing the risk of hydroplaning by road vehicles. When a curbstone is present, a gutter may be formed by the convergence of the road surface and the vertical face of the sidewalk; otherwise, a dedicated gutter surface made of concrete may be present.

Depending on local regulations, a gutter usually discharges in a storm drain whose final discharge falls into a detention pond (in order to remove some pollutants by sedimentation) or into a body of water.

Not all streets have gutters, and they are most often found in areas of a city which have high pedestrian traffic. In past centuries when urban streets did not have sanitary sewers, gutters were made deep enough to serve that purpose as well.

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Wikipedia