View source for Drainage

{{Short description|Removal of water from an area of land}}
{{otheruses}}
[[File:Hdpe pipe installation.jpg|thumb|[[High-density polyethylene]] pipe installation in a [[storm drain]] project, Mexico.]]

'''Drainage''' is the natural or artificial removal of a surface's water and [[groundwater|sub-surface water]] from an area with excess water. The internal drainage of most [[agricultural]] soils can prevent severe [[Waterlogging (agriculture)|waterlogging]] (anaerobic conditions that harm root growth), but many [[Soil|soils]] need artificial drainage to improve production or to manage water supplies.

==History==

===Early history===
[[File:A drain at Lothal.jpg|thumb|Remains of a drain at [[Lothal]] circa 3000 BC]]

The [[Indus Valley Civilization]] had [[sewerage]] and drainage systems. All houses in the major cities of [[Harappa]] and [[Mohenjo-daro]] had access to water and drainage facilities. Waste water was directed to covered [[gravity sewer]]s, which lined the major streets.<ref>{{cite book |last=Arthur Coterell |url=https://archive.org/details/encyclopediaofan0000unse_d6g9 |title=The Encyclopedia of Ancient Civilisations |publisher=Rainbird Publishers |year=1980 |isbn=0-7112-0036-X |pages=176–178 |url-access=registration}}</ref>

===18th and 19th century===
[[Image:Tank Stream.jpg|thumb|[[Tank Stream]], a historical drain in the City of Sydney, Australia]]

The invention of hollow-pipe drainage is credited to Sir Hugh Dalrymple, who died in 1753.<ref>{{cite web |date=1705 |title=Broadside eulogy dedicated to Patrick, Earl of Marchmount, Sir Hugh Dalrymple, and others |url=http://digital.nls.uk/broadsides/broadside.cfm/id/15893 |access-date=5 April 2015 |publisher=National Library of Scotland Digital Gallery}}</ref>

==Current practices==
Simple infrastructure such as open drains, pipes, and [[berm]]s are still common. In modern times, more complex structures involving substantial earthworks and new technologies have been common as well.

===Geotextiles===
New storm water drainage systems incorporate [[geotextile]] filters that retain and prevent fine [[Particle size|grains]] of [[soil]] from passing into and clogging the drain. Geotextiles are synthetic textile fabrics specially manufactured for [[civil engineering|civil]] and [[environmental engineering]] applications. Geotextiles are designed to retain fine soil particles while allowing water to pass through. In a typical drainage system, they would be laid along a trench which would then be filled with coarse [[granular material]]: [[gravel]], [[sea shells]], stone or [[rock (geology)|rock]]. The geotextile is then folded over the top of the stone and the trench is then covered by soil. [[Groundwater]] seeps through the geotextile and flows through the stone to an outfell.<ref>{{Cite web |last= |date=2023-05-12 |title=5 ways geotextile drainage fabric can improve your drainage system |url=https://geosyntheticsmagazine.com/2023/05/12/5-ways-geotextile-drainage-fabric-can-improve-your-drainage-system/ |access-date=2026-05-02 |website=Geosynthetics Magazine |language=en-US}}</ref> In high groundwater conditions a perforated plastic ([[Polyvinyl chloride|PVC]] or [[Polyethylene|PE]]) pipe is laid along the base of the drain to increase the volume of water transported in the drain.

Alternatively, a prefabricated plastic drainage system made of [[High-density polyethylene|HDPE]],<ref>{{Cite web |title=Terrain FUZE HDPE - HDPE Above Ground Drainage System {{!}} Polypipe Building Services {{!}} BIM Library |url=https://source.thenbs.com/en/product/terrain-fuze-hdpe/ti4gophzsPCEXNsHyjTtWs/hvLdmYNAGRQX2CoVdnMGok |access-date=2026-05-02 |website=source.thenbs.com |language=en}}</ref> often incorporating geotextile, [[Coir|coco fiber]] or [[Cloth|rag]] [[filter (water)|filter]]s can be considered. The use of these materials has become increasingly more common due to their ease of use, since they eliminate the need for transporting and laying stone drainage aggregate, which is invariably more expensive than a synthetic drain and concrete liners.

===21st century alternatives===
[[Seattle|Seattle's]] Public Utilities created a pilot program called Street Edge Alternatives Project. The project focuses on designing a system "to provide drainage that more closely mimics the natural landscape prior to development than traditional piped systems".<ref name="seattle">{{Cite web |title=Street Edge Alternatives (SEA Streets) Project |url=http://www.seattle.gov/UTIL/About_SPU/Drainage_&_Sewer_System/Natural_Drainage_Systems/Street_Edge_Alternatives/index.asp |url-status=dead |archiveurl=https://web.archive.org/web/20081205095408/http://www.seattle.gov/util/About_SPU/Drainage_%26_Sewer_System/Natural_Drainage_Systems/Street_Edge_Alternatives/index.asp |archivedate=Dec 5, 2008 |website=Seattle.gov}}</ref>
The streets are characterized by ditches along the side of the roadway, with plantings designed throughout the area.
An emphasis on non-curbed sidewalks allows water to flow more freely into the areas of permeable surface on the side of the streets. Because of the plantings, the run off water from the urban area does not all directly go into the ground, but can also be absorbed into the surrounding environment.
Monitoring conducted by Seattle Public Utilities reports a 99 percent reduction of storm water leaving the drainage project.<ref name=seattle/>

[[Sustainable urban drainage systems]] (SUDS) are designed to encourage contractors to install drainage system that more closely mimic the natural flow of water in nature.  Since 2010 local and neighbourhood planning in the UK is required by law to factor SUDS into any development projects that they are responsible for.<ref>{{Cite web |title=Sustainable drainage systems |url=https://www.bgs.ac.uk/geology-projects/suds/ |access-date=2026-05-02 |website=British Geological Survey |language=en-GB}}</ref>

[[Slot drain]]age is a channel drainage system designed to eliminate the need for further pipework systems to be installed in parallel to the drainage, reducing the environmental impact of production as well as improving water collection. [[Stainless steel]], [[concrete]] channel, PVC and HDPE are all materials available for slot drainage which have become industry standards on construction projects.

===In the construction industry===
The [[civil engineer]] is responsible for drainage in construction projects.<ref>{{Cite web |date=2026-02-05 |title=It's time for civil engineers to rethink sustainable drainage |url=https://www.ice.org.uk/news-views-insights/inside-infrastructure/time-civil-engineers-rethink-sustainable-drainage |access-date=2026-05-02 |website=Institution of Civil Engineers (ICE) |language=en}}</ref> During the construction process, they set out all the necessary levels for [[road]]s, [[street gutter]]s, drainage, [[culvert]]s and sewers involved in [[construction]] operations.
<!-- There are roughly 38,700 technical people, including site/civil engineers, employed in the construction industry. Most work for a [[general contractor]] or a specialist [[subcontractor]]. -- Where? In the whole world?-->

Civil engineers and construction managers work alongside [[architect]]s and supervisors, planners, [[quantity surveyor]]s, and the general workforce, as well as subcontractors. Typically, most jurisdictions have some body of [[drainage law]] to govern to what degree a landowner can alter the drainage from their parcel.

Drainage options for the construction industry include: 
* Point drainage, which intercepts water at [[gullies]] (points).<ref>{{Cite web |last= |first= |title=Point drainage |url=https://www.birco.com/point-drainage/ |access-date=2026-05-02 |website=www.birco.com |language=en}}</ref> Gullies connect to drainage pipes beneath the ground surface, so deep excavation is required to facilitate this system. Support for deep trenches is required in the shape of planking, strutting or shoring.
* Channel drainage, which intercepts water along the entire run of the channel. Channel drainage is typically manufactured from concrete, steel, polymer or composites.<ref>{{Cite web |last= |first= |date=2022-06-21 |title=What are channel drains? Everything you need to know |url=https://www.buildandplumb.co.uk/blog/what-are-channel-drains/ |access-date=2026-05-02 |website=Build and Plumb {{!}} Ideas & Advice - |language=en-GB}}</ref> The interception rate of channel drainage is greater than point drainage and the excavation required is usually much less deep.
The surface opening of channel drainage usually comes in the form of [[gratings]] (polymer, plastic, steel or iron) or a single slot (slot drain) that run along the ground surface (typically manufactured from steel or iron).

=== In retaining walls ===
Earth retaining structures such as [[retaining wall]]s also need to have [[groundwater]] drainage considered during their construction. Typical retaining walls are constructed of impermeable material, which can block the path of groundwater. When groundwater flow is obstructed, hydrostatic [[water pressure]] buildups against the wall and may cause significant damage. If the water pressure is not drained appropriately, retaining walls can bow, move, and fracture, causing seams to separate. The water pressure can also erode soil particles, leading to voids behind the wall and [[sinkhole]]s in the above soil. Traditional retaining wall drainage systems can include [[French drains]], drain pipes or [[Weep hole|weep holes]]. To prevent soil erosion, geotextile filter fabrics are installed with the drainage system.

=== In planters ===
Drainage in planters refers to the implementation of effective drainage systems specifically designed for plant containers or pots. Proper drainage is crucial in planters to prevent waterlogging and promote healthy plant growth. Planter Drainage involves the incorporation of drainage holes, drainage layers, or specialized drainage systems to ensure excess water can escape from the planter. This helps to prevent [[root rot]], water accumulation, and other issues that can negatively impact plant health. By providing adequate drainage in planters, it supports optimal plant growth and contributes to the overall success of gardening or landscaping projects.<ref name="drainservice">{{cite web|title=4 Expert Tips for Perfect Planter Drainage
|url=https://drainservice.org/4-expert-tips-for-perfect-planter-drainage/|website=drainservice.org|date=15 April 2023 |access-date=July 1, 2023 |archive-date=June 30, 2023|archive-url=https://web.archive.org/web/20230630162340/https://drainservice.org/4-expert-tips-for-perfect-planter-drainage/ |url-status=live}}</ref>

Drainage options for the planter include: 
* Surface drains are typically used to manage runoff from paved surfaces, such as sidewalks and parking lots. Catch basins, which collect water and debris, are connected to underground pipes that carry the water away from the site.<ref name=drainservice/>
* Subsurface drains, on the other hand, are designed to manage water that seeps into the soil beneath the planting surface. [[French drains]], which are gravel-filled trenches with perforated pipes at the bottom, are the most common type of subsurface drain. [[Trench drain|Trench drains]], which are similar but shallower and wider, are also used in some situations.<ref name=drainservice/>

==Reasons for artificial drainage==
[[Image:MagomeDrainage.jpg|thumb|upright|An agricultural drainage channel outside [[Magome-juku|Magome]], [[Japan]] after a heavy rain. Protuberances create turbulent water, preventing sediment from settling in the channel.]]

[[Wetland]] soils may need drainage to be used for [[agriculture]].<ref>{{Cite web |date=2025-04-28 |title=Constructed farm wetlands |url=https://www.wwt.org.uk/our-work/wetland-conservation-unit/resources/constructed-farm-wetlands |access-date=2026-05-02 |website=WWT |language=en}}</ref> In the northern United States and Europe, [[glaciation]] created numerous small [[lake]]s, which gradually filled with [[humus]] to make [[marsh]]es. Some of these were drained using open [[ditch]]es and trenches to make [[muck (soil)|muckland]]s, which are primarily used for high-value crops such as [[vegetable]]s.

The world's largest project of this type has been in process for centuries in the [[Netherlands]]. The area between [[Amsterdam]], [[Haarlem]] and [[Leiden]] was, in [[prehistoric]] times, swampland and small lakes. Turf cutting ([[peat]] [[mining]]), [[subsidence]] and shoreline [[erosion]] gradually caused the formation of one large lake, the [[Haarlemmermeer]], or lake of Haarlem. The invention of wind-powered [[Windpump|pumping engines]] in the 15th century permitted some of the marginal land drainage. Still, the final drainage of the lake had to await the design of large [[steam-powered]] pumps and agreements between regional authorities. The lake was eliminated between 1849 and 1852, creating thousands of km<sup>2</sup> of new land.

[[Coastal plains]] and [[river deltas]] may have seasonally or permanently high [[water table]]s and must have drainage improvements if they are to be used for agriculture. An example is the [[flatwoods]] [[citrus]]-growing region of [[Florida]], United States. After periods of high rainfall, drainage pumps are employed to prevent damage to the citrus groves from overly wet soils. [[Rice]] production requires complete water control, as fields must be flooded or drained at different stages of the crop cycle.<ref>{{Cite web |title=Mid-season rice paddy drainage |url=https://www.unccd.int/best-practice/mid-season-rice-paddy-drainage |access-date=2026-05-02 |website=UNCCD |language=en}}</ref> The Netherlands has also led the way in this type of drainage by draining lowlands along the shore and pushing back the sea until the original nation has been greatly enlarged.

In moist climates, soils may be adequate for cropping with the exception that they become [[Waterlogging (agriculture)|waterlogged]] for brief periods each year, from [[snow]] melt or from heavy [[rain]]s. Soils that are predominantly [[clay]] will pass water very slowly downward. Meanwhile, plant roots suffocate because the excessive water around the roots eliminates air movement through the soil.

Other soils may have an [[impervious]] layer of mineralized soil, called a [[hardpan]], or relatively impervious rock layers may underlie shallow soils. Drainage is especially important in [[Fruit tree|tree fruit]] production. Soils that are otherwise excellent may be waterlogged for a week of the year, which is sufficient to kill fruit trees and cost the productivity of the land until replacements can be established. In each of these cases, appropriate drainage carries off temporary flushes of water to prevent damage to [[annual plant|annual]] or [[perennial plant|perennial]] crops.

Drier areas are often farmed by [[irrigation]], and one would not consider drainage necessary. However, irrigation water always contains minerals and [[salt (chemistry)|salt]]s, which can be concentrated to toxic levels by [[evapotranspiration]]. Irrigated land may need periodic flushes with excessive irrigation water and drainage to control [[soil salinity]].
{{wide image|Drainbankstown.jpg|1800px|A typical drain in [[Bankstown, New South Wales]], Australia|alt=A typical drain in Bankstown, New South Wales}}

==See also==
* Surface drainage of the land
** [[Drainage system (geomorphology)]], pattern of natural drains, streams, rivers, etc.
**[[Land drainage in the United Kingdom]] -  a legal and operational term in the UK to define a range of functions and responsibilities of drainage boards.
** [[Surface runoff]], surface runoff of excess rainfall from the land
** [[Drainage system (agriculture)]], land forming or land shaping to enhance the drainage from the soil surface in agricultural land
** [[Contour plowing]], controlling runoff and [[soil erosion]]
* Subsurface ([[groundwater]]) drainage
** Horizontal drainage by pipes and ditches
*** [[Tile drainage]]
** Vertical drainage by wells
*** [[Well drainage]]
*** [[Watertable control]]

Otherwise:
{{div col|colwidth=30em}}
* [[Bar ditch]]
* [[Building construction]]
* [[Deep drainage]]
* [[Drain commissioner]]
* [[Drain (plumbing)]]
* [[Drainage basin]] or watershed
* [[Drainage divide]] or watershed
* [[Drainage equation]]
* [[Drainage research]]
* [[Geomorphology]]
* [[Hydrologic Evaluation of Landfill Performance]]
* [[Hydrology]]
* [[John Johnston (farmer)|John Johnston]], who introduced land drainage to the [[United States]].
* [[Plumbing]]
** [[Domestic water system|Potable cold and hot water supply]]
** [[Septic system]]s
** [[Plumbing drainage venting|Sewage traps, drains, and vents]]
* [[Rain gutter]]
* [[Retaining wall]]
* [[Sewage collection and disposal]]
* [[Soil salinity control]] by subsurface drainage
* [[Storm drain]]
* [[Stormwater]]
* [[Trench drain]]
* [[Trencher (machine)]]
* [[Urban exploration]]
{{div col end}}

==References==
{{Reflist|30em}}

==External links==
*{{Commonscat-inline}}
*{{Wiktionary-inline}}

{{Agricultural water management}}
{{Infrastructure}}
{{Authority control}}

[[Category:Drainage| ]]
[[Category:Water management]]