[Tagging] waterway=wadi problem

[Tod Fitch]

On Jan 14, 2015, at 8:28 AM, Wolfgang Zenker wrote:

> * Mateusz Konieczny <matkoniecz at gmail.com> [150114 15:45]:
>> waterway=wadi is used (18 180 times) and has some support (for example JOSM
>> and default map style).
> 
>> During implementing rendering of intermittent=yes I discovered major
>> problem with this tag -
>> the same waterway=wadi may be used for completely dried up waterway,
>> intermittent stream, intermittent major river and intermittent ditch.
> 
>> Therefore - it seems that using waterway=river/canal/stream/ditch/drain +
>> intermittent=yes is clearly superior to using waterway=wadi.
> 
> In my experience a wadi will go from "completely dried up waterway" or
> "small stream" to a raging river within a few seconds after some
> rainfall upstream, and back to its former self within a few hours.
> Depending on the location, these rainfall events might very well be
> a few years apart. When I tag an "intermittent stream" I usually
> have something more benign in mind, like a stream that only exists
> during the spring snow melt and is dry the rest of the year, but
> maybe that is only my interpretation of an intermittent stream.
> 
> Wolfgang
> 
Your description of wadi matches many things locally called a "wash" in the U.S. desert southwest. Yet when I suggested that I tag those as wadi I was shot down. :)

I've taken to tagging them as waterway=river/stream (depending on width) and intermittent=yes. And, yes, in these cases "intermittent" may mean that it only carries water for an hour or two every couple of years.

The United States Geological Survey (USGS) topographic maps will show them as either a line of sand or an intermittent waterway depending, I think, on whim of the cartographer.

A while back I submitted a change to the rendering for OsmAnd to recognize intermittent=yes as without that desert areas look way to wet. For the paper maps that I generate I've also created a Mapnik style that recognizes intermittent=yes and uses the USGS style intermittent rendering. It would be nice if the default rendering at www.openstreetmap.org would also recognize the intermittent tag.