A drainage system is a network of artificial drains and ditches which are used to remove surplus water from an area.



Drainage networks are commonly associated with field systems and managing water flow on farmed land (see: water meadow). Drainage systems were also dug for industrial purposes like draining bogs for peat cutting and redirecting waterways to power watermills. Drainage networks vary in overall layout and ditch size, and in whether or not they incorporate natural water courses.
Drainage channels are common features in cultivated woodlands, especially ones on clay soils that become seasonally waterlogged. Irregular, sinuous systems would have been dug around existing trees and are often earlier in date. Networks that are more regular in plan were likely laid out in the 18th and 19th century after a period of forest clearing.