[Tagging] intermittent vs seasonal

johnw johnw at mac.com
Sat Oct 3 09:14:31 UTC 2015


> On Oct 3, 2015, at 3:23 PM, Mateusz Konieczny <matkoniecz at gmail.com> wrote:
> 
> Where wiki recommends converting all waterway=wadi to waterway=river or
> stream with intermittent=yes?
> 
> On http://wiki.openstreetmap.org/wiki/Tag:waterway%3Dwadi <http://wiki.openstreetmap.org/wiki/Tag:waterway%3Dwadi> there is
> "For intermittent waterways use waterway=river/waterway=stream +
> intermittent=yes. For valleys natural=valley"


It is not a valley. it’s the flat sandy are inside the valley. and it usually extends out from a valley into a plain.  and the wash is singularly named, inside the gorge or out on the plain.

A wash/wadi is a named feature in OSM for a reason. Because it isn’t a river, nor is used/treated like one is - mainly because they occur in a very different kind of climate. They are (informally?) called “washes” in the US. They are basically flood control channels for the desert, and only receive water in flash flood conditions, like avalanches. Most of the ones I know have roads up them. Not along them. Not across them. In them. And you can go out driving on them year round - except for the 1-2 days a year (usually for 6-12 hours) randomly when they would have water from rain in the mountains that created the desert. This varies with the El-nino- La nina cycle in California, but basically the wash is open and dry ~ 360 days a year. 

 The wash is the overflow channel/cover for the tiny tiny creek (usually underground) that suddenly receives a massive torrent of dangerous flash flood water from the mountains, which disappears in the course course of a single day, usually only a very few times a year. Only once in my life, thanks to a massive El Nino storm set lasting a month, have I seen water in a wash longer than a day.

They are called washes and not streams nor rivers for a reason - because their dominant state and useful state is dry and flat sand.


Please see this as a example of a wash. This is the biggest wash I know of - Carrizo Wash. I learned to drive in this area when I was 12.  This is what people do in washes. https://www.youtube.com/watch?v=d4frwfCnCTg <https://www.youtube.com/watch?v=d4frwfCnCTg>

Carrizo Creek is is in the gorge. It is an intermittent stream (not seasonal). The gorge holds the wash. The wash is over the creek.  **The wash is the sandy area, 10-400m wide**  at the bottom. The gorge disappears, leaving the wash by itself.  Here is the wash where it leaves the mountains and heads to the open desert. the “valley” walls are 2m high for this 400m wide wash after it leaves the mountains here. Imagine 2m of water flowing through it for 6 hours. Then disappearing.

https://www.google.com/maps/@32.848337,-116.20125,3a,79.3y,182.86h,77.26t/data=!3m4!1e1!3m2!1sb-zcFlLD-gtgKjdDCWdIFw!2e0 <https://www.google.com/maps/@32.848337,-116.20125,3a,79.3y,182.86h,77.26t/data=!3m4!1e1!3m2!1sb-zcFlLD-gtgKjdDCWdIFw!2e0>

The wash, with the intermittent creek hidden in the sand below, heads to a sink in the middle of the desert - the Salton Sea. 

Please note the tire tracks. This is because it is the only practical place to drive in the desert (the rest is craggy and rocky). 

Why don’t we call all canals rivers? drains?rivers too? There’s no room for wadi/wash in the tagging scheme? 

The people who live with washes and wadis call them washes and wadis and representing them in OSM as a river is ignoring regional conventions and trying to shoehorn temperate ideas into desert tagging. And rendering them like a river makes a crappier map. 

Like tagging a motorway as a river. 


Javbw
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