Hi Volker, Thank you for your answer
Le dim. 22 mars 2020 à 23:09, Volker Schmidt <vosc...@gmail.com> a écrit : > > > On Sun, 22 Mar 2020 at 19:09, François Lacombe <fl.infosrese...@gmail.com> > wrote: > >> Hi Volker, >> ... >> Fully disposed to make any improvement to wiki according to those points. >> > > Thanks, Francois. > > There is possibly a language bias (error?) in the use of tunnel=flooded. > I am not a native speaker, but "flooded" to me means at least "more water > than normal", and from this discussion it seems that we are talking about > the normal presence of water in these structures. > This objection was raised as it could mean it's more than normal, but no better term has been proposed so far https://wiki.openstreetmap.org/wiki/Talk:Proposed_features/Hydropower_water_supplies#tunnel.3Dflooded.3F Flooded has been taken as simpler "Full of water". "A flooded tunnel is an artificial structure intended to channel water on a significant distance. Its dimensions and length allow human to fit inside but safe walking is impossible due to high amount of water or other fluid expected in operation." Tag use tunnel=flooded: 2 in the UK, > >> Many, if not the majority of the UK Inland Waterways canals have no > tow-path. > > Then tunnel=flooded is more appropriate. > No, definitely not. These tunnels are not "flooded" at all, the water > level in them is carefully controlled > Filling a tunnel with water doesn't prevent you to control the level. It just means you won't be able to walk in and stay dry. > (The original method of powering the boats in these canals were men laying > on their back and "walking" with their feet upwards along the tunnel > ceiling. The French canals, being constructed later, generally did have > tow-paths also in the tunnels see for example the Tunnel_de_Mauvages > <https://www.google.com/url?sa=i&url=https%3A%2F%2Ffr.wikipedia.org%2Fwiki%2FTunnel_de_Mauvages&psig=AOvVaw3UK-_RmcKBM_5fKTGMZyjW&ust=1584997257128000&source=images&cd=vfe&ved=0CA0QjhxqFwoTCOijlIn9rugCFQAAAAAdAAAAABAS>. > I remember when I was a boy my father showed me the tractors pulling the > ships through the old tunnel near Arzwiller in Alsace on the same canal) > They are uniformly tagged (correctly) as waterway=canal and tunnel=yes. > I mentioned them in the context that tunnel=yes does not imply a tow-path. > Agreed that tunnels with tow-paths like Tunnel de Mauvages should be tagged with tunnel=yes. > I had glanced at your Hydropower water supplies proposal, but I think I > failed to intervene on three specific points: > > 1. The first one are the inverted siphons (botte sifone > <https://it.wikipedia.org/wiki/Botte_sifone>, pont-siphon > <https://fr.wikipedia.org/wiki/Pont-siphon>), which are > gravity-pressurised always-water-filled sections of non-navigable canals. I > usually map them as culverts, and i have just started to add the new tag > culvert=inverted_siphon to the first three of them. > > No problem with this If air can't get inside due to lowest elevation of inverted siphon, this would be waterway=pressurised. > > 1. The second point is that the distinction between water-filled and > part-filled water conducts is problematic: culverts that are frequently > used to conduct free-flowing drains, ditches, irrigation canals, freshwater > canals under roads can be anything from empry to fully filled (and slightly > pressurised) depending on precipitations. > > Finding a waterway punctually pressurised because of exceptional conditions and another pressurised on purpose makes a *big difference*. waterway=pressurised covers only the second situation where the intake of conduit (tunnel or pipeline) is placed on purpose under the water level as to prevent air coming inside. For instance, you'll find hydropower plant operator stopping immediately its turbines if water goes under a certain level in upstream dam lake because it would allow air to get inside headrace and penstocks and finally cause big damages on its equipment. > > 1. waterway=pressurised cannot be used together with waterway=canal > for the inverted-siphon situation > > Agreed, because waterway=canal is expected to be free flowing https://wiki.openstreetmap.org/wiki/Key:waterway#Values I see no problem to: * alternate canal/pressurised on different waterway sections depending on their condition. * use waterway=canal on a culvert that isn't expected to be pressurised even if this occurs on exceptional conditions. I agree this could be more clear on wiki and will require more description and examples Would you like to collaborate to give some pictures or situations you are familiar with? All the best François
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