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> Looking at the US NHD estuary is broadly defined <br></div><div><br></div><div>NOAA keeps track of the estuaries. And the states have fairly extensive data available: <br></div><div><a href="https://www.coastalatlas.net/?option=com_jumi&view=application&fileid=8&e=20&Itemid=107">https://www.coastalatlas.net/?option=com_jumi&view=application&fileid=8&e=20&Itemid=107</a></div><div><br></div><div>Estuary is a generic term that covers five basic types, which have quite different in the characteristics that define them, beyond the general 'river going into the see' aspect. A Norwegian fjord and a mudflat can both be estuaries. Once you identify the type ( and since they are hugely important to global fisheries and other stakeholders, almost certainly someone has already identified the type <a href="https://oceanservice.noaa.gov/education/kits/estuaries/estuaries04_geology.html">https://oceanservice.noaa.gov/education/kits/estuaries/estuaries04_geology.html</a> ), how the various feature boundaries are to be handled in OSM isn't too difficult. <br></div><div>
</div><div><br></div><div>The ocean edge of the estuary if defined by if it is tide-dominated, wave-dominated, or river-dominated. That determines if you have have a Bay of Fundy <a href="https://en.wikipedia.org/wiki/Bay_of_Fundy">https://en.wikipedia.org/wiki/Bay_of_Fundy</a> estuary, Bay of Fundy, a Mississippi River type of delta,
or a Columbia River situation where the river channel pretty much extends to the sea. That can be generally indicated in a tide table according to three basic buckets >4 meters, 2-4 meters, and less than 2 meters. <br></div><div><br></div><div>
<div>>>>> but I think we'll have problems defining it? <br></div><div><br></div><div>Only if you try to make the same scheme apply to all five (
<a href="https://oceanservice.noaa.gov/education/kits/estuaries/media/supp_estuar04_coastal.html"><span class="gmail-textlink">coastal plain</span></a>, <a href="https://oceanservice.noaa.gov/education/kits/estuaries/media/supp_estuar04_barbuilt.html"><span class="gmail-textlink">bar-built</span></a>, <a href="https://oceanservice.noaa.gov/education/kits/estuaries/media/supp_estuar04_delta.html"><span class="gmail-textlink">deltas</span></a>, <a href="https://oceanservice.noaa.gov/education/kits/estuaries/media/supp_estuar04_techtonic.html" class="gmail-textlink">tectonic</a> and <a href="https://oceanservice.noaa.gov/education/kits/estuaries/media/supp_estuar04_fjord.html"><span class="gmail-textlink">fjords</span></a> ).</div><div><br></div><div>The 'cartographic' derived concept that there is just some sort of simple idealized 'coastline' is a fiction, and at the scale of human beings, not a very useful one. There isn't land and sea, there is land, sea, and a third 'coastal', which is land and sea changing several times a day and dramatically on a monthly and annual basis. <br></div><div><br></div><div>Michael Patrick</div><div>Data Ferret<br></div><div><br></div></div></div></div>