[Tagging] Flood mark or high water mark

Graeme Fitzpatrick graemefitz1 at gmail.com
Wed Aug 8 01:33:40 UTC 2018


On 8 August 2018 at 05:00, Robert Szczepanek <robert at szczepanek.pl> wrote:
>
>
> Before making any changes in wiki I would like to find final agreement on
> that topic.
> "Flood level" (highest water table) is usually only one of several
> informations we can find on "flood mark". Others can be date of flood,
> inscription, etc.
> Physical object mapped in OSM is rather mark, not just water/flood level.
> So "historic=flood_mark" is probably more generic.


Yes, flood_mark would be a better wording than flood_level


>
>> Yes.
>> Complication .. a historic king tide combined with a storm event may be
>> considered a historic flood level.
>> But 'normal' high tides should be part of the water way tagging system.
>>
>>
> This can be sometimes hard to distinguish. But tide+storm I would consider
> rather as flood event - probably higher level comparing to periodic tides.
>

Quite definitely - a storm surge becomes a flood, not just a very high tide


> In such a case we can find in on place two types of marks:
> * historic=highwater_mark - with information about periodic highest water
> level (no date provided),
> * historic=flood_mark - with information about flood event (with date)
> So existence of date on such mark could be a good information for proper
> tag assignment. I'm not familiar with tides, so please correct me if this
> is not the case.


High tide is defined as " the highest level which can be predicted to occur
under average meteorological conditions and any combination of astronomical
conditions"
https://www.ausmarinescience.com/marine-science-basics/tides/highest-astronomical-tide/

IMHO, the high tide mark as such shouldn't really be shown in OSM as it
should be the line marking either the coastline or riverbank.

Thanks

Graeme
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