A survey of international and some national lexicons indicates that the two terms 'ditch' and 'drain' are equivalent used in the context of liquids from the smallest to largest scales.
The term 'drain' however seems mostly to apply at the interface where the water transitions from the substrate ( soil ) to free running water, down flow from that the water is 'channeled' through ditches, fluves, shutes, spillways, canals, and a multitude of functional confinements. One of the earliest ( 1920 ) legal references to British and American law notes this equivalence, and the following an extract from a 2017 global standard saying basically the same thing. UNESCO-WMO International Glossary of Hydrology at https://unesdoc.unesco.org/ark:/48223/pf0000221862 -World Meteorological Organization, United Nations Educational, Scientific and Cultural Organization: "...will be useful to national hydrological services as well as educational and research institutions throughout the world – especially for those who require more than one language for understanding or communicating information about the field of hydrology. In establishing recognized international equivalents of hydrological terms, our goal is also to minimise misinterpretations and consolidate the foundation for stronger international cooperation." 407 ditch see also drain Man-made small open channel constructed through earth or rock for the purpose of lowering and/or conveying water 415 drain see also ditch Conduit or small open channel by which water is removed from a soil or an aquifer, by gravity, in order to control the water level or to remove excess water. Ditto with the USGS and the UK Ordnance Survey: For example, OS MasterMap Topography Layer User guide - "Water - Water features are defined as features that contain, delimit or relate to real-world objects containing water. The physical water features shown in OS MasterMap Topography Layer include: ... drains and ditches; ... Dam, ditch, dock, double, down, drain D, Double ditch or drain DD" ... a look see at a lot of OS web map products show the same thing. In the case of the UK, a vast amount of property lines are encoded as these ditches and drains, so they formalized this equivalence to accommodate whatever the locals called them. There is no dependence on the size, width, depth, etc. A perhaps extreme example ( due to heavily mechanized agriculture in the U.S. ), but still illustrative is that the USDA construction guidelines make the following distinctions: Small ditches ( maximum top width 15 feet ) Medium-sized ditches ( top width 15 to 35 feet ) Large ditches ( more than 35 feet top width) In SE Asian rice production, their largest ditches probably would be in the 'small' category compared to the U.S. I don't read Chinese, Japanese, Korean, etc. but I'm sure they have a couple thousand years of established vocabulary for their field water handing. The modern agricultural water handling industry ( what you would get if you asked somebody to install a 'ditch' or a 'drain' in a field makes a distinction as follows ( echoing the 'interface' idea above ): Ditch — A man-made, open drainage-way in or into which excess surface water or groundwater drained from land, stormwater runoff, or floodwaters flow either continuously or intermittently Drain — A buried slotted or perforated pipe or other conduit (subsurface drain) or a ditch (open drain) for carrying off surplus groundwater or surface water. Ditches aren't restricted to water use. Sometimes they are there because the material was sued to form an embankment, or used for road surface ( 'borrows' in the USA ), animal control barriers, access control, boundary marking, spill prevention and control of loose soils and aggregate slides. And in all the water literature, in the U.S, and U.K., they pretty much also freely used 'drainage ditch', not just simply 'ditch. Predominantly, if the cut is not further improved from the native material, it seems to be called a ditch, if structure is added like concrete lining, wooden bank sides, maybe it will get a more specific term. Economics dictates that for the most part these enhancements only occur over limited lengths for flow control, erosion, obstacles, evaporation, etc. Drainage structure means a device composed of a virtually non-erodible material such as concrete, steel, plastic or other such material that conveys water from one place to another by intercepting the flow and carrying it to a release point for water management, drainage control or flood control purposes. Looking at the aerial photography majority of 'drains' in the OS based web maps, they are pretty much 'swales' ( https://en.wikipedia.org/wiki/Swale_(landform) ), without the distinctive edges of a 'ditch'. In conclusion: For legacy tagging, ditch/drain should be left alone because of equivalence. For new tagging, ditch or drainage_ditch, ditch:drainage, or 'whatever' scheme should indicate it is a ditch for conduction of water, and 'drain_open' or some such to distinguish it from subterranean drains ( despite being buried, these are actually sometime more visible than the ditches on aerial / sat photography ). Anything 'drain' should be confined to where the ground interfaces with a open channel. But a singular 'ditch' would suffice. Because of global variety and local conditions, there should be no 'size' distinction, or distinction because of structural presence, materials, etc. Local terminology takes precedence, at the highest level it is available. While a dictionary might be a useful start for determining a meaning, there is almost always some better source of definitions in a specific domain, culture, and region, and location. The U.N., E.U., U.K., Scotland, and down to Renfrewshire all have documentation of what terms mean in those local contexts, for example. Almost always, a single word will be immediately overloaded when used world wide.Human languages have compound words, adjectives, verbs and adverbs for a reason, and tagging schemes have equivalents. Michael Patrick Data Ferret
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