[Tagging] waterway=wadi problem

[johnw]

I’ll make one up in the next few hours. I want to research wadis in other countries to make sure I’m not assuming my regional experience is misrepresenting the whole. 

Javbw

> On Jan 15, 2015, at 3:24 PM, Mateusz Konieczny <matkoniecz at gmail.com> wrote:
> 
> Can you consider making proposal for waterway=wadi on wiki?
> Or maybe other tag, as waterway=wadi is frequently used to mark 
> intermittent streams?
> 
> Currently http://wiki.openstreetmap.org/wiki/Tag:waterway%3Dwadi <http://wiki.openstreetmap.org/wiki/Tag:waterway%3Dwadi> is
> not mentioning anything like that.
> 
> Note, I am not disputing usefulness of term wadi. I am disputing usefulness
> of waterway=wadi tag due to lack on any agreed definition and description on
> OSM wiki.
> 
> 2015-01-15 3:41 GMT+01:00 johnw <johnw at mac.com <mailto:johnw at mac.com>>:
> I strongly disagree. A wadi is usually only an active river through very rare flash flood events, and almost never any other time.  Entire biomes are defined by the presence of (and situated in) a wadi. 
> 
> In america, the words Arroyo and wash roughly translate into wadi, and because of the ambiguous nature of arroyo, the term wadi is used for a wash or arroyo when referring to a usually dry stream/riverbed that is dangerous in flash flood conditions. 
> 
> my experience with washes stems from the Southern California Desert, where most of the state park would basically be covered in blue, if washes were somehow labeled as rivers - some are 100m across.  Whole road systems exist in the washes (and are reestablished purely by use after a flood), as the rest of the land is almost impassable. 
> 
> I have driven a couple thousand miles in a roughly 50x50 mile box over a hundred or so driving trips, and only on 3 occasions was water ever present, and at that time, the roads were completely impassable (a meter or so of water filled up the Carrizo wash 30m wide).
> 
> Although several famous arroyos (like the LA River) are now basically man-made drainage ditches, mapping desert areas properly requires the wadi tag, as they are different from intermittent rivers - in the fact that water in the “bed" is *never expected* - even seasonally - and if present it is a dangerous flash flood. There is never an in-between state of what you would call “a river” for longer than a day. - as it disappears almost immediately as soon as the flood is over (except in the most exceptional of weather conditions).  - kind of like an avalanche is only an avalanche while it is moving, or an earthquake is is an event. 
> 
> A wadi is a place where flash floods occur. It is not an intermittent river - it isn’t really seasonally wet, and doesn’t provide any real expectation that water will be present (except deep underground) - because they are located in places where rain itself is unexpected for most of the year. 
> 
> A wadi has an expectation of always being dry, except for the rare and unpredictable flash flood. t and in that case, you should assume it is a dangerous, and impassable place. 
> 
> I think, espcially since it is defined and used so heavily, and has a different connotation than a river - even a intermittent one, it should be kept. 
> 
> a wash near Borrego springs, CA (ironwood wash, Tubb canyon). it drains to a sink in the middle of the desert (the white spot in the upper right)
> 
> https://www.flickr.com/photos/javbw/11091366554/in/set-72157638113734675 <https://www.flickr.com/photos/javbw/11091366554/in/set-72157638113734675>
> 
> https://goo.gl/maps/fpSxE <https://goo.gl/maps/fpSxE>
> 
> Javbw
> 
> 
>> On Jan 14, 2015, at 11:45 PM, Mateusz Konieczny <matkoniecz at gmail.com <mailto:matkoniecz at gmail.com>> wrote:
>> 
>> 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.
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