[OSM-talk] Mapping rivers that flow into/through lakes?

Rory McCann rory at technomancy.org
Thu Feb 22 21:59:00 UTC 2018

Hi mappers,

What's the best way to map rivers that flow into lakes, especially when
another river flows through it? Should they be connected?

When a river flows through a lake, you can map a waterway=river way
through it, to be "topoligcally complete". Or would it be better to add
ways (w/o waterway tag) to the river relation?

When a tributary river joins another, join the central waterway=river
ways together. But what if a river drains into a lake with a  "central
river" through it? Should you connect that river to the central river?
It makes topological sense.

If you asked someone "Where does this river end?" they'd probably point
to where it joins the lake. Connecting the river to the "central river"
breaks this. And it can result in odd long ways. I might have gone a
little OTT here (
) or here (

Without joining the ways, then a data consumer will have to do
complicated extra processing to deduce that one river "flows into" the
other? (River X ends on the shore of a lake, River Y flows through the
lake, so connect X to Y). Is that "good enough"?



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