There is another type of a combination of open waterway, underground waterway, and pressurised waterway/pipeline: a siphon (see [1]). This is a frequent situation here in northern Italy. They came in all sizes, and there are hundreds of them around here. The technical trick with these is that the lower part of the siphon has reduced cross section, and thus is pressurized, to increase the water speed to flush out any deposits or avoid them in the first place . This is a nice example [2]. Location on the map: [3]
[1] https://fr.wikipedia.org/wiki/Pont-siphon [2] http://www.acquerisorgive.it/wp-content/uploads/2014/01/IMG_0121.jpg [3] https://osm.org/go/0ICdUgNrl-?m=&node=1549226607 On 12 February 2018 at 16:44, François Lacombe <fl.infosrese...@gmail.com> wrote: > Hi everybody, > > The hydro power waterway proposal has been updated to take care of several > useful comments made during the last vote. > > Here is a changelog : > - Moving from waterway=drain to waterway=canal since a drain is mainly > intended to remove superfluous water. A canal carries water from A to B for > a particular usage. It can be overground and underground with tunnel=*, as > not to break existing underground ways with waterway=canal on them > - Introducing mill race concept thanks to Janko Mihelic (mill race = head > race + mill + tail race) > - Introducing tunnel=headrace, tailrace and canal=headrace, tailrace, > spillway > - Moving from waterway=spillway to waterway=canal + canal=spillway > > waterway=pressurised stays in the document currently, I still believe this > value is useful and bring consistency for hydrology mapping, as a > continuation of rivers/stream inside tunnels and pipelines. > > I've updated pictures : > https://wiki.openstreetmap.org/wiki/File:Waterway_flows.png > https://wiki.openstreetmap.org/wiki/File:Waterway_manmade_structures.png > > The second one shows how various are waterways and why a waterway=* value > is useful to get all of them without leak. > > Depending on comments, voting may restart shortly. > > All the best > > François > > _______________________________________________ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging > >
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