[Tagging] Coastline for rivers, estuaries and mangroves?

Christoph Hormann osm at imagico.de
Mon Sep 3 20:20:58 UTC 2018


On Monday 03 September 2018, Kevin Kenny wrote:
> It would certainly need to be above Haverstraw - the current there
> http://tbone.biol.sc.edu/tide/tideshow.cgi?site=Haverstraw+%28Hudson+
>River%29%2C+New+York+Current shows significant tidal reversal.  I
> haven't found a gaging station farther upriver that reports tidal
> currents. Croton Point, where the river broadens to form the Tappan
> Zee, would probably be the lower limit. Even that seems unreasonably
> far upriver.
>
> The tidal range increases as you move upstream from there. The
> greatest tidal range in the entire river is at Troy. One Native
> American name for the river was "Mahicantuck" which means, more or
> less, "the river flows both ways."

I am not familiar with the specific situation but tidal reversal is not 
incompatible with the rule i formulated.

And as said for low volume tidal rivers a relative salinity criterion 
might work better - but this does not work with larger volume rivers 
where this could put the lower limit pretty far out into the ocean.

> The estuarine situation will always be hard to deal with, and I think
> we'll simply need to have rough guidelines and then trust the
> judgment of the locals.

This is essentially the situation we have right now.  Judgement of local 
mappers is usually fine (with the exception of political cases like the 
Rio de la Plata).  Most problems occur because armchair mappers 
misinterpret the local situation or when inexperienced mappers are 
unaware of the significance of distinguishing between ocean and 
riverbank mapping.

-- 
Christoph Hormann
http://www.imagico.de/



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