[Tagging] [OSM-talk-be] how to map a fr:talus?

André Pirard A.Pirard.Papou at gmail.com
Fri Nov 24 21:04:59 UTC 2017

On 2017-11-24 10:55, ralph.aytoun at ntlworld.com wrote:
> I have had a look on the Wallonia website. If you zoom out you will
> see that this feature runs exactly parallel to the road to the south
> of it. It is man made. It would have been created at the same time as
> the road. It was done to raise the road to a higher level as a flood
> defence against the river to the north. I do not know but it may be
> that there is a retaining structure of stone or concrete to strengthen
> it but is covered with soil and grass.
> The tag for this could be /man_made=dyke/ with /material=soil/.
> You will see that the farmland to the south of the road has something
> similar. This is not flood defence, it is terraced farming to stop the
> run off of water on sloping farmland.
> The tag for this could be /barrier=retaining_wall/ with
> /material=stone/soil/ (or whatever material is used)
> Hope this has been helpful.
> Ralph
Thank you, Ralph.
If you look down below (as people started to write bottom up in the XXth
century) you will see that I found Projet de canal Meuse et Moselle
seeming to confirm what I wrote: that talus is the remnants of that old
canal, commonly called "canal de l'Ourthe", washed away by the frequent
flooding of the Ourthe and of various fate along its course.
So, what I should normally do is map a canal.
But as nobody ever saw a canal with a single bank looking like a talus,
that would get me in troubles.  Not counting that the rendering, even if
we cannot tag "for" it, would try to fill it with water and cause even
more flooding ;-)

So, good-bye canal, what it has now become is a crumbled bank, a
crumbled wall I suppose..

That is just as queer, so, unless you change your mind, I'll tag it man
according to your repeated consent, but only as a single way at the top
of the slope I suppose.
But I'll name it an old canal's bank.

Thanks to all,


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> *From: *André Pirard <mailto:A.Pirard.Papou at gmail.com>
> *Sent: *Thursday, November 23, 2017 10:29 PM
> *To: *OpenStreetMap Belgium <mailto:talk-be at openstreetmap.org>
> *Cc: *Tag discussion, strategy and related tools
> <mailto:tagging at openstreetmap.org>
> *Subject: *Re: [Tagging] [OSM-talk-be] how to map a fr:talus?
> On 2017-11-23 17:26, joost schouppe wrote:
>     2017-11-23 16:48 GMT+01:00 André Pirard <A.Pirard.Papou at gmail.com
>     <mailto:A.Pirard.Papou at gmail.com>>:
>         Hi,
>         I'm looking for how to map what is called in French a talus
>         <http://www.cnrtl.fr/definition/talus> (Google's translation).
>         I would call this a 1.8m simple step running for some reason
>         for several 100s meters across meadows.
>         Steep slope. There are "top of slope" and "bottom of slope"
>         lines. Rest is perfectly flat either side.
>         It might be the remnants of a old canal's bank whose other
>         side would have been eroded by the often overflowing nearby river.
>         A "talus" made of plain ground is often frequent at one side
>         of a path or track.
>         According to the wiki, it's not a "scree" nor a "shingle".
>         It's much less matter specific.
>         So what?
>         I'll use "scree" unless/until I hear of better for a French talus.
>         Cheers
>         André.
>     I'm not entirely sure this is what you have in mind, but in the
>     cases where it is associated with roads, I've seen
>     historic=hollow_way (when the slope is caused by the fact that
>     there's an old road), and "embankment" or "cutting" when the slope
>     is deliberatly constructed. In other cases, I've seen what I think
>     you describe mapped as natural=cliff, which is obviously wrong,
>     but does get the message accross. For example where sand or rock
>     was quarried this is common to see on the map. I'm hoping someone
>     has seen better ideas.
> Thanks for all your fast answers from which I had to choose the first
> one to reply to.
> A photo was asked. I might go back there to make one, but you wouldn't
> see more that the surface of a meadow looking like this on a long
> distance, at varying steepness and width.
>                _________
>           /
>          /
> ________/
> It can be seen on this map share
> <http://geoportail.wallonie.be/walonmap#BBOX=233801.45736786586,233864.69291100363,138369.75440413086,138396.60966617474#SHARE=5EAB0363BC0C4A92E053D0AFA49D3CB8>,
> pan it to the left and right.
> The two striped, faint lines are the upper and lower edges (rims,
> levels) from the BE SPW(allonie) PICC numerical imagery
> <wms:http://geoservices.wallonie.be/arcgis/services/TOPOGRAPHIE/PICC_VDIFF/MapServer/WmsServer?SERVICE=WMS&VERSION=1.1.1&FORMAT=image/png8&TRANSPARENT=TRUE&REQUEST=GetMap&STYLES=&SRS=%7Bproj%7D&WIDTH=%7Bwidth%7D&HEIGHT=%7Bheight%7D&BBOX=%7Bbbox%7D&LAYERS=0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29>
> (JOSM) overlay allowing me to map it. As you zoom out, you will see
> that the aerial photo is darker along that line.
> The Cartoweb background (Fond de Plan) draws it as the typical "behind
> which to hide" line of old military maps.
> Well, in OSM parlance, it's not a cree because there is no cliff (1),
> not a shingle because there is no sea and not an embankment because
> there is no road to be an attribute of.
> Well, as I said it, what I'm facing seems to be, as I found more
> specifically, the remnants of this old canal @ N°12
> <https://fr.wikipedia.org/wiki/Projet_de_canal_Meuse_et_Moselle#N.C2.B012_Devant_Rosi.C3.A8res>.
> The river often overflows as high as above the road. When the water
> goes back, it washes the left bank of the canal towards the river but
> the right bank is mostly just overflown.
> So, there's nothing in OSM for that precisely.
> Would man_made=dyke be the most resembling and acceptable with an
> explanation note?
> Thanks and TIA,
> Cheers
> André.
> (1) there's a very beautiful one, but at the other side of the river,
> called "La Roche aux Faucons" (Falcons' Cliff).

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