[Tagging] Rio de la Plata edit war

muralito at montevideo.com.uy muralito at montevideo.com.uy
Mon Aug 3 18:56:53 UTC 2020

----- Mensaje original -----
> De: "Christoph Hormann" <osm at imagico.de>
> Para: "Tag discussion, strategy and related tools" <tagging at openstreetmap.org>
> Enviados: Sábado, 1 de Agosto 2020 14:52:40
> Asunto: Re: [Tagging] Rio de la Plata edit war

> On Friday 31 July 2020, Andy Townsend wrote:
>> For what it's worth, neither extreme position looks the best answer
>> to me - looking at the salinity change between river to ocean at
>> https://www.sciencedirect.com/science/article/pii/S0307904X07000716
>> (see
>> https://www.sciencedirect.com/science/article/pii/S0307904X07000716
>> for the key picture) and looking at
>> https://de.wikipedia.org/wiki/Datei:Rio_de_la_Plata_BA_2.JPG suggests
>> a location some way between the two.  Despite the NASA photo it looks
>> like there isn't a "step change" in salinity - and of course values
>> will fluctuate based on winds and tides etc.
> Surface salinity is not a good universal measure for the transit between
> the riverine and the maritime domain because
> a) depending on the threshold you would exclude large maritime areas
> like the Baltic Sea, Hudson Bay or the Sea of Azov.
> b) at the mouth of a river salinity often varies significantly between
> the surface layer and deeper water because saltwater is heavier.
> Suspended particles are also often not a good measure because we are
> usually talking about very fine particles that stay suspended for a
> long time and in shallow water currents can re-suspend silt from the
> bottom as well.  The presence of suspended particles is therefore an
> indication of a lack of large volume dilution of the water in the area,
> not of the dominance of river water over sea water in general.  See for
> example
> http://maps.imagico.de/#map=7/32.361/122.212&lang=en&l=sat&ui=10
> where strongly visible turbidity reaches up to more than 50km from the
> shore into the open sea.
> As i wrote in my old proposal on the transit placement looking at the
> cross section of the river and the resulting average water flow
> velocity due to discharge gives you a relatively good idea about the
> situation.  In case of the Rio de la Plata you have an average
> discharge of 22000m^3/s.  At the claimed baseline you have an average
> water depth of about 20m and a width of more than 200km that is an
> average waterflow velocity of 6mm/s.  At Montevideo with a width of
> about 100km and a depth of about 8m you get an average velocity of
> 3cm/s.  That is still smaller than typical coastal currents induced by
> tides and wind (which the paper you cited confirms).  But you are not
> that far off any more and around where the average water depth is about
> 5m you will have reached the lower limit my proposal suggests.
> I still think the people best qualified to make the assessment where
> exactly the transit is best placed are those with local knowledge, who
> have first hand knowledge of the effects of waves, tides and currents
> on the shore over the course of the year as long as their perspective
> is not dominated by political considerations (i.e. they are able to
> look at this purely from a physical geography perspective).

Right. For all this reasons the best place to put the coastline is in the line.
The only reason to continue tagging the coastline inland in the river is to render it,
 or to see it in the render like some people thinks it should be, but it is not the real coastline.

The scientific view, and what can be experienced or observed here is that the coastline ends in Punta del Este. 
And the line to Punta Rasa is a good average of the limit. Where should be put the coasline if not here?



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