[Tagging] Clearer definition of tunnel=flooded: when should it be used instead of tunnel=yes or tunnel=culvert?

François Lacombe fl.infosreseaux at gmail.com
Sun Mar 22 23:33:48 UTC 2020


Hi Volker,

Thank you for your answer

Le dim. 22 mars 2020 à 23:09, Volker Schmidt <voschix at gmail.com> a écrit :

>
>
> On Sun, 22 Mar 2020 at 19:09, François Lacombe <fl.infosreseaux at 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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