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Ditches at the Ouse Washes nature reserve.

• For use of the ditch as obstacles for horses, see ditch (obstacle)

A ditch is usually defined as a small to moderate depression created to channel water. A ditch can be used for drainage, to drain water from low lying areas, alongside roadways or fields, or to channel water from a more distant source for plant irrigation. A trench can be defined as a long narrow ditch. Ditches are commonly seen around farmland especially in areas that have required drainage, such as The Fens in the UK and the pro-water management Netherlands.

Roadside ditches can provide a hazard to motorists, especially in poor weather conditions. It is not an uncommon sight in some rural areas to see cars, motorbikes, or bicycles that have crashed into ditches, or to hear of such accidents.

Sometimes this word is employed as a Halloween word meaning grave as in the 1993 Disney film Hocus Pocus.

In military engineering and fortification, a distinction is made between a ditch and a trench. A ditch is an obstacle, designed to slow down or break up an attacking force, while a trench is cover, intended to provide protection to the defenders. In Medieval fortification, a ditch was often constructed in front of a defensive wall to hinder mining and escalade. When filled with water, such a defensive ditch is called a moat. Later star forts of Vauban and others comprised elaborate networks of ditches and parapets, carefully calculated so that the soil for the raised earthworks was provided, as nearly as possible, entirely by the excavations whilst also maximising defensive firepower. Today ditches are obsolescent as an anti-personnel obstacle, but are still often used as anti-vehicle obstacles (see also berm).

Drainage ditches play major roles in agriculture throughout the world. Improper drainage systems accelerate water contamination, excessively desiccate soils during seasonal drought, and become a financial burden to maintain. Industrial earth moving equipment facilitates maintenance of straight drainage trenches, but entrenchment results in increasing environmental & eventually profound economic costs overtime[1].

Sustainable channel design can result in ditches that are largely self maintaining due to natural geomorphological equilibrium. Slowed net siltation and erosion result in net reduction in sediment transport. Encouraging development of a natural stream sinuosity and a multi-terraced channel cross section appear to be key to maintain both peak ditch drainage capacity, and minimum net pollution and nutrient transport[2].

Flooding can be a major cause of recurring crop loss -- particularly in heavy soils-- and can severely disrupt urban economies as well. Subsurface drainage to ditches offers a way to remove excess water from agricultural fields, or vital urban spaces, without the erosion rates and pollution transport that results from direct surface runoff. However, excess drainage results in recurring drought induced crop yield losses and more severe urban heat or desiccation issues.

Controlled subsurface drainage from sensitive areas to vegetated drainage ditches makes possible a more optimal balance between water drainage and water retention needs. The initial investment, allows a community to draw down local water tables when and where necessary without exacerbating drought problems at other times[3].

1. See also hypoxia, dead zone, nonpoint source pollution, desertification, and urban heat island.

2 Geomorphic Characteristics of Drainage Ditches in Southern Minnesota, and the concept of a Two-Stage Ditch Design (Brad Hansen, Bruce Wilson, Joe Magner, and John Nieber) http://d-outlet.coafes.umn.edu/presentations/DrainForum06/J.%20Nieber-2-stage%20ditch%20design.pdf

3 Drainage Water Management Updates (G. Sands) http://d-outlet.coafes.umn.edu/presentations/DrainForum06/G.%20Sands-WTM%20Updates.pdf See also Watertable control