Open drainage systems, also called natural drainage systems, consist of uncovered channels or ditches that pick up wastewater flows. These systems are often unlined, but perform better if lined with concrete, brick or mortar. Apart from wastewater, open drainage system also serve as stormwater run-offs, and should be designed to accommodate heavy flows. These systems are not suitable for transporting sewage. Open drainage systems are more often used on farm lands than in urban areas.
Unlined open drainage systems are easier and less expensive to set up than covered piping. Installation is also less labour-intensive, as a farmer can create channels and ditches on his own, provided he has the right equipment. Maintenance of these systems is also not as labour-intensive as pipes that need to be dug up for reparations, so it works out cheaper in the long run too.
Open drains can receive overland flow and thus have the advantage of serving as surface drainage. These drains collect more silt and rubbish than pipes and allow increased residency of water to break down pollutants. Open drains parallel to roads can be used to guide water off the roadway, ensuring road safety in wet conditions.
As open drains are more easily accessible than pipes, maintenance of these drains is simple. Inspections and cleaning operations are easier to perform as these drains are not buried. If open lined drains are correctly designed, they should not require expensive or major repair. Regular inspections prevent major issues from arising. Grass or other vegetation should be planted along the sides of the drains to prevent erosion.