[Tagging] [Tagging ] How to tag a paleochannel of a river

Peter Elderson pelderson at gmail.com
Sat Mar 13 09:57:10 UTC 2021

Dutch polders are extensive hydrological systems, designed to maintain constant water levels under all circumstances (mainly by pumping out the water, hence the vast amount of water mills still present in Nederland as heritage). The land in the polders is used for housing (including major cities), military, industry, airports, forestry, leisure, tourism, even though the original and still the main use is agricultural. So landuse=polder may not be ideal. I think it's more like a man_made feature. Or water level based boundaries. 

Peter Elderson

> Op 13 mrt. 2021 om 09:57 heeft stevea <steveaOSM at softworkers.com> het volgende geschreven:
> A fascinating discussion, as I know oxbows in rivers and the oxbow lakes they might create, though I am unclear on why or whether OSM might, do or should tag these.  Usually in cases like these (this is me, but I think it wide practice), I tend towards the side of "be generous, allowing the wider, more expansively-described tagging."  So, "yes" to oxbow, whether on a river or as a lake created by what I understand to be "the oxbow process."  A hydrologist could fully explain this process (which is part geological, part hydrological, IIRC).  As Bert suggests, a wiki about this might also describe a hydrologist-informed lifecycle including that these can and do turn into swamps over a decades-to-centuries time scale.
> Similarly, polder.  There is such a thing and I'm a bit surprised we haven't developed a tag for it (even if it IS simply landuse=polder), although let's be careful with landUSE as a key for this, it might imply all polders "act like a polder," which may or may not be true.
> What I have never heard before is "paleochannel," and US English is my native tongue.  (The word does not appear in my US English dictionaries, either).  I'm sure it is really "something," (perhaps only in a highly specialized or technical realm, it has that sort of feel about it) though how it differs from "oxbow," I don't know.  But "oxbow" is a real word.  (It is also a U-shaped collar of an ox yoke, hence being applied to rivers and the lakes resulting from the oxbow geological / hydrological process).
> There is also something about a river called the "thalweg" (German, valley/dale + way) meaning "a line connecting the lowest points of successive cross-sections along the course of a valley or river."  Some places use this as a more-exact legal boundary in larger rivers that define boundaries.
> Fascinating, the places OSM goes.
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