[Tagging] Coastline for rivers, estuaries and mangroves?

Kevin Kenny kevin.b.kenny at gmail.com
Mon Sep 3 19:32:08 UTC 2018


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."

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.
On Mon, Sep 3, 2018 at 2:51 PM Christoph Hormann <osm at imagico.de> wrote:
>
> 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
> influence).
>
> 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
> area).
>
> --
> Christoph Hormann
> http://www.imagico.de/
>
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