[Tagging] Coastline for rivers, estuaries and mangroves?

Christoph Hormann osm at imagico.de
Mon Sep 3 18:50:27 UTC 2018

On Monday 03 September 2018, Kevin Kenny wrote:
> Imagico's proposal is perhaps objective, but surely doesn't match
> perception in my part of the world. It seems odd that the 'coastline'
> must extend upward to https://www.openstreetmap.org/way/90929525 -
> but that is, according to Imagico's definitions, simultaneously the
> lowest and highest permissible limit. [...]

Then you have misunderstood the proposal.

With the Hudson river obviously the tidal case applies so you have the 
lower limit as:

With significant tides the coastline should go upstream at least to a 
point where on waterflow is going downstream for a significantly longer 
part of the tidal cycle than it goes upstream due to raising tide. 

This is evidently always below the upper limit (range of tidal 

I can't say for sure where i would place the lower limit in case of the 
Hudson - The Narrows is quite definitely too low - but the current 
closure seems fine.

For low volume tidal rivers (i.e. without a salt wedge and no 
significant influence of the water volume on the ocean salinity) it 
would also be possible to define the lower limit through salinity (not 
in absolute terms but as a fraction of the open ocean salinity in the 

Christoph Hormann

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