[Tagging] waterway=wadi problem

[johnw]

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

Javbw


> On Jan 14, 2015, at 11:45 PM, Mateusz Konieczny <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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