[Tagging] waterway=wadi problem

[johnw]

That’s all of San Diego - the storm drain system is so anemic - I’ve hydroplaned my car down the freeway (“Surfing interstate 5”), and forded a few “intermittent” rivers before I moved to Japan. here in Japan, torrential rain is really a non-issue most of the time - whereas a few cm of rain in Southern California means death on the roads and flooding underpasses. maybe it’s all the bald tires, oily roads, and people going 30-40km/h over what they should be driving.  One wonders.  ^_^

Javbw

> On Jan 16, 2015, at 9:27 AM, Eugene Alvin Villar <seav80 at gmail.com> wrote:
> 
> Given the current discussion, I wonder if roads that are usually flooded during heavy rainfall should be also be tagged as waterway=river/stream and intermittent=yes. ;-)
> 
> On Fri, Jan 16, 2015 at 7:27 AM, John F. Eldredge <john at jfeldredge.com <mailto:john at jfeldredge.com>> wrote:
> I would recommend expanding the definition of "intermittent streams" to include not only streams that have a regular, seasonal water flow but also streams in desert areas that exist only when a rare storm comes along. The topography is the same, the tendency of water to run downhill is the same, only the frequency of rainfall is different.
> 
> -- 
> John F. Eldredge -- john at jfeldredge.com <mailto:john at jfeldredge.com>
> "Darkness cannot drive out darkness; only light can do that. Hate cannot drive out hate; only love can do that." -- Martin Luther King, Jr.
> 
> 
> 
> 
> On January 15, 2015 3:13:38 AM Christoph Hormann <chris_hormann at gmx.de <mailto:chris_hormann at gmx.de>> wrote:
> 
> On Thursday 15 January 2015, johnw wrote:
> >
> > 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.
> 
> Well - that would be a useful concept of a wadi but it has two problems:
> 
> * current use of the tag is very different from that, you can see that
> quite well when you look at the taginfo map:
> 
> https://taginfo.openstreetmap.org/tags/waterway=wadi#map <https://taginfo.openstreetmap.org/tags/waterway=wadi#map>
> 
> the uses in Europe for example are probably almost always seasonal.
> 
> * sporadic waterflow is very difficult to determine for the mapper.
> This is especially true for northern Africa where climate got a lot
> drier in the last few thousand years and as a result there are many
> permanently dry valleys that still look like being formed by waterflow
> but that have not seen significant waterflow in the last hundred years.
> 
> My suggestion would probably be to stop rendering waterway=wadi in a way
> implying waterflow, encourage mappers to use intermittent/seasonal
> where this is known and reserve waterway=wadi - despite the then
> misleading key - for valleys where waterflow is unknown.
> 
> --
> Christoph Hormann
> http://www.imagico.de/ <http://www.imagico.de/>
> 
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