planet-grouped-ends : Handling of River split in multiple branches for hydropower and transportation canals - and - River that cross waterfall or rapids polygon

[pierzen]

Below are links where continuity is broken on the planet-grouped-ends map. Images below are from JOSM Waterways Style (OpenStreetMap data). Each example show valid cases with water continuity on the same watershed. planet-grouped-ends does not interpret these as a continuity in the same watershed and stop continuity for some of the lines.

power generators and transportation canals, Bourg-les-Valences
upward river splits in 3 from left to right [river, hydro-power canal, transportation canal]
hydro-power waterway=canal splits in 6 [waterway=canal] that cross the dam polygon where they connect to power generators. All these lines regroup afterward to the downward river
https://waterwaymap.org/#tiles=planet-grouped-ends&map=14.67/44.96183/4.87154

power generators and transportation canals La Tourette
upward river splits in 3 from left to right [river, transportation canal, hydro-power canal]
hydro-power waterway=canal splits in 6 [waterway=canal][man_made=pipeline] that cross the dam polygon where they connect to power generators. All these lines regroup afterward to the downward river
https://waterwaymap.org/#tiles=planet-grouped-ends&map=15.88/44.676865/4.786672

power generators, Seyssel
upward river splits on left in two [waterway=river], on right in 6 [waterway=pressurized][usage=penstock], then 3 [waterway=canal][usage=tailrace]. All regroup afterward to the downward river
https://waterwaymap.org/#tiles=planet-grouped-ends&map=17/45.971251/5.834251

spillways, Gouin reservoir
upward river splits in 4, 4 [waterway=canal][usage=spillway] crosses the dam polygon - regroup afterward to the downward river
https://waterwaymap.org/#tiles=planet-grouped-ends&map=17.85/48.353751/-74.097809

river crosses waterway=waterfall polygon
https://waterwaymap.org/#tiles=planet-grouped-ends&map=16.65/47.317304/-73.748947

[amandasaurus]

Thanks for theses examples. Let's try to figure out what's going on. Perhaps the OSM data needs to be changed, or the WWM.org filter rules needs updating.

[amandasaurus]

spillways, Gouin reservoir
upward river splits in 4, 4 [waterway=canal][usage=spillway] crosses the dam polygon - regroup afterward to the downward river
https://waterwaymap.org/#tiles=planet-grouped-ends&map=17.85/48.353751/-74.097809

Here's, the river does split into 4 ways (one to the left & 2 to the right), however it then flows directly into a simple waterway=canal,layer=-1 way. That way then flows into a waterway=canal,usage=spillway, which WWM's tag filters would be included. Likewise the 3 tributories flow into 3 ways without the waterway=canal and no usage tag (a, b, c), which then flow into 3 with usage=spillway. Are you sure the small initial waterway=canals are tagged correctly? 😉

[amandasaurus]

power generators and transportation canals, Bourg-les-Valences
upward river splits in 3 from left to right [river, hydro-power canal, transportation canal]
hydro-power waterway=canal splits in 6 [waterway=canal] that cross the dam polygon where they connect to power generators. All these lines regroup afterward to the downward river
https://waterwaymap.org/#tiles=planet-grouped-ends&map=14.67/44.96183/4.87154

A little upstream of that power station, the Canal de Bourg-lès-Valence (tagged waterway=canal) splits off from the L'Isère river. Since the canal is tagged with only waterway=canal, WWM.org ignores this entire side branch (you can see [nothing of the canal on WWM there. The upstream value of L'Isère (now 11,707 km), just continues into Le Rhône. I don't think this is a bug. No upstream value is “lost”, there are no “dead ends”. The topology of the waterway network isn't broken. Yes, there is a side canal of (I presume) flowing water, which is not shown on this map. But I can't see a way to get that into WWM without including all canals, which I'm reluctant to do.

[amandasaurus]

power generators and transportation canals La Tourette
upward river splits in 3 from left to right [river, transportation canal, hydro-power canal]
hydro-power waterway=canal splits in 6 [waterway=canal][man_made=pipeline] that cross the dam polygon where they connect > to power generators. All these lines regroup afterward to the downward river
https://waterwaymap.org/#tiles=planet-grouped-ends&map=15.88/44.676865/4.786672

Here, Le Rhône, a waterway=river splits into 6 rivers, which then flow through the dam in 6 ways, e.g. this which is taggged waterway=canal, but also man_made=pipeline. WWM does record a high ”end point” here. I'd like to solve that.

[amandasaurus]

Currently, WWM excludes waterway=pressurised, after a bug report #47, there is also a bug report to put it back in #58. There's also a osm community forum about it. 😖😖😖

[pierzen]

Gouin reservoir, I corrected regrouping canals in 4 [waterway=canal][usage=spillway].

For other cases, how to assure correct waterway typology, with confirmation that the waterway flows downward ? A simple solution would be to use the key flow_direction=forward that is used in combination with man_made=pipeline ? or new usage keys ?

If key key flow_direction is not a solution

For hydropower canals segments not yet described by, usage keys, is the solution to simply use the tag waterway=river or create a specific usage ? usage=hydropower_canal ?

The same with transportation canal. To confirm frew flow downward should we create a new usage ? usage=transportation_canal ?

And finally, a solution needed also for waterway=pressurized.

[amandasaurus]

For other cases, how to assure correct waterway typology, with confirmation that the waterway flows downward ? … in combination with man_made=pipeline

I've added waterway=canal,man_made=pipeline to the list of approved tags for flowing water. With your tagging changes, those 2 examples should be included.

[amandasaurus]

If key key flow_direction is not a solution

I'm very reluctant to add a tag like that. the flow of a waterway should be deduced from the direction of the way. And I don't want something that's like “this is a type of object like X, but it's really a Y”. It feels like a trolltag or (mis)tagging for the waterwaymap.

[pierzen]

If key key flow_direction is not a solution

I'm very reluctant to add a tag like that. the flow of a waterway should be deduced from the direction of the way. And I don't want something that's like “this is a type of object like X, but it's really a Y”. It feels like a trolltag or (mis)tagging for the waterwaymap.

I also prefer to take into account the waterway direction. Below is the example of Champlain canal where this rule is applied. It connects two watershed, the Saint-Lawrence river north and the Hudson river south. At the highest point of the canal, there is a river to provide water to the top sections. All other rivers are in distinct watershed.
https://waterwaymap.org/#map=13/43.29294/-73.56295&tiles=planet-grouped-ends

To assure correct typology, contributors have assured that direction of each canal segment points in the direction corresponding to the water flow and the feeder canal is only connected to one of these two segments. At the highest point, we have way 164250572 that point in the direction of the Hudson river, and way 1219087266 that points in the direction of the Lake Champliain, Richelieu / Saint-Lawrence river.

Side Note Some contributors are quite micro-mind-mapping adding ,tidal=no , rapids=no and deep_draft=no to Champlain Canal members. I dont think this will help us !

[pierzen]

river crosses waterway=waterfall polygon
https://waterwaymap.org/#tiles=planet-grouped-ends&map=16.65/47.317304/-73.748947

The section Barriers on waterways in thekey:waterway wiki page lists waterway tags that are Barrier structures. The Waterway=canal is used to indicate the continuitiy of the waterflow through these structures and these barriers should be ignored in the evaluation of the waterflow continuity :
polygons waterway=[dam, weir, waterfall, rapids, lock_gate, sluice_gate, floodgate, debris_sceen, security_lock, check_dam].

In the wiki page, the key waterway=waterfall is described as being used only as a point. But following redesign of waterway keys moving them to the water key, there subsist old tagging schemes in the database. The object of the Waterways map is not to force remapping / retagging and waterway=[waterfall, rapids] polygons should be simply ignored.