Why don't we have a tag for smalll freshwater channels?

Natural waterways are distinguished by their size (jump over width) as being a river or a stream which makes sense although this distinction is a bit vague.

For man made freshwater channels we only have one tag “canal”, although these waterways can also be tiny (< 30 cm) or huge (> 10 m). As most people do not understand a tiny channel to be a “canal” this leads to mistagging of small man made freshwater channels as “stream” or “drain” which are both not correct.

A good example are mill races which can be found in many places although the mills have ceased operating sinse long. Such mill races are man made and often in between 0.5 to 1.5 meters wide (easy to jump over). They are no streams as they are not naturally formed and they are no drains as they do not carry superflous or waste water.

The same applies to small channels like the “Freiburg Bächle” which are actually tagged as “drain” which they definitely not are.

To distinguish these small freshwater channels from big canals for shipping etc. I would appreciate to have a separate tag (similar to “stream”) for those being not too wide to jump over.

What are your thoughts?

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In my area, we call irrigation channels “canals” (usually too wide to jump over, too narrow and shallow for a boat) but I don’t tag them as waterway=canal since I understand that to mean a wider, navigable feature.

Have you looked at waterway=ditch for something like this? The wiki is a little inconsistent in what that means but I find it closer than canal for these little man-made waterways.


I suppose we could resurrect the flume proposal as waterway=flume as tagging has moved on a bit since then.

How would this be distinguishable from you typical waterway=drain for a casual mapper though? They often have very similar construction.

Part of the issue here is the orthogonality between the construction of a waterway and the use of a waterway. A small (artificial) waterway can have surprisingly many functional/decorative/natural uses, and be dug/built in many ways. Often waterways built using the exact same techniques serve very different purposes.

With the relatively few waterway= tags in use (drain, stream, ditch, ++), it is clear that many different things have been grouped together using some shared characteristics.


Agreed, I might even go as far as to say that in an ideal world waterway= would describe the overall general physical nature (width, depth, perhaps typical flow rate) and other tags would drill down into the details like lining, purpose, construction, etc.

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…but in practice, I just want to draw a line through the field, tag it waterway=ditch, and move on to map other things I care more about.

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Agreed, this is the pragmatical aspect of mapping small waterways. Most mappers do not want to waste time to measure width, depth and flowrate of a small water channel nor of a stream or river and that is why we have more generic tags for those.

Under this aspect those tags in use make sense to me:

drainage channel wide, lined = drain
drainage channel small, unlined = ditch
drainage channel very small, prefabricated = drainage_gutter (as proposed here).

natural waterway wide = river
natural waterway narrow = stream

artificial (fresh)waterway wide = canal
artificial (fresh)waterway small = ???

From that point of view we are just missing a tag for small freshwater channels. Still looking for a good idea how to tag those … :thinking:

Apparently most mappers think about small waterways in the same way as sbre

so I will not push this issue further.

What I am going to do is to use the waterway=ditch tag for these objects which appears to be the “de facto” handling at the time being (although not encouraged by the wiki as it contradicts the original definition of “ditch”).

To distinguish these freshwater channels from exess water ditches I will add


so if any time we may create a separate tag for those it will be easy to identify these channels for retagging.

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I don’t think these have to be particularly wide? But I would support something like gutter for really small (<approx 150mm) ones.

The issue here are small freshwater channels not too wide to jump over, similar to waterway=stream, but not from natural origin. The physical appearance is the same like waterway=ditch, but they are carrying freshwater instead of exess or waste water.

Gutter has been used already for very small prefabricated channels as discussed here: Tagging of a steel gutter inlet