[OSM-talk] WaterwayMap.org is really going downhill

[Amanda McCann]

[WaterwayMap.org](https://waterwaymap.org/), shows how rivers & streams are connected in OSM. It's proven pretty popular with mappers. It's been pretty undirected from the start, and I'm happy to say it's really going downhill now.

Previously waterways were joined together purely based on topology, ignoring direction. River bifurcations occur more often than I thought, and connect large water systems together. e.g. [casiquiare canal](https://github.com/amandasaurus/waterwaymap.org/issues/55) or the [Garonne/Ebro](https://en.osm.town/deck/@amapanda/112240136848653730) (causing [tagging questions](https://community.openstreetmap.org/t/is-there-a-common-tag-for-underground-infiltrated-watercourses/111558)).

So, I've added a new calculation which groups ways together **based on the direction they flow**, and which “end point” they flow into. All rivers & streams which flow into the same river mouth will get coloured the same.

## [Explore the Downhill Waterway Map](https://waterwaymap.org/#tiles=planet-grouped-ends) _(or select “Natural Waterways (downhills)” from the Settings)_

It's got some bugs. 🐞 (but they're cute aquatic bugs)

When a river splits, the total upstream is split equally, and mapping mistakes can cause a lot of upstream value to stop some random field somewhere. All river segments upstream can be assigned to that end point, and appear split off from other parts of the river downstream. It's already been [seen](https://discord.com/channels/413070382636072960/413070502580453387/1257454307977203773) in the [Murray-Darling river system in Australia](https://waterwaymap.org/#map=5.64/-31.123/145.889&tiles=planet-grouped-ends&len=500..inf). Use the [Waterway Ends map](https://waterwaymap.org/ends) (prev. on [forum 💬](https://community.openstreetmap.org/t/the-end-of-waterway-map/108632)) to find where it ends. I hope that people will fix up these mapping mistakes, and this will happen much less. Perhaps I can improve this by looking at the `name` of the waterway.

The [software which converts the geojson to vector tiles](https://github.com/felt/tippecanoe) has to drop some line segments, causing gaps at certain zoom levels. Could this type of map be better with raster tiles? 😳🙊

I'll be talking about WaterwayMap.org at [SotM Europe 2024](https://stateofthemap.eu/) in Łódź, Poland on [Sun. 10:00am](https://cfp.openstreetmap.org.pl/state-of-the-map-europe-2024/talk/K8LF7U/). if you're around say hi. 🙂 (But first, the Alps are calling… 🥾🎒🏔️)


# See also

* [News about WaterwayMap.org](https://en.osm.town/@amapanda/tagged/WaterwayMapOrg) can be found on Mastodon/Fediverse (incl. [Atom/RSS feed](https://en.osm.town/@amapanda/tagged/WaterwayMapOrg.rss)):
* This code is on Github: [`amandasaurus/waterwaymap.org`](https://github.com/amandasaurus/waterwaymap.org). [New issue reports](https://github.com/amandasaurus/waterwaymap.org/issues/new) are welcome.
* The programme which generates it is [`osm-lump-ways`](https://github.com/amandasaurus/osm-lump-ways)
* [WaterwayMap on the OSM Forum](https://community.openstreetmap.org/tag/waterwaymaporg)
* [Waterway Loops](https://waterwaymap.org/loops) ([forum 💬](https://community.openstreetmap.org/t/the-wonders-of-early-medieval-fore-abbey-and-osm-river-topology-today-i-e-waterwaymap-org-is-going-around-in-circles/107497)) which show probably tagging mistakes.

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