[Tagging] tagging floodplain

Kevin Kenny kevin.b.kenny+osm at gmail.com
Mon Sep 26 00:45:14 UTC 2016

There was a proposal a while back for a 'water=intermittent' tag, which
might be revised for the situation, perhaps with some additional tagging to
describe whether the area is inundated seasonally or only sporadically.

For the 'official' flood control boundary, there are also
boundary=protected_area tags of classes 12 and 15.

Either of these could be combined with the appropriate landuse=*, of course.

Just a handful of possibilities - I'm not claiming that any of them is

On Sun, Sep 25, 2016 at 8:00 PM, Colin Smale <colin.smale at xs4all.nl> wrote:

> On 2016-09-26 01:18, Warin wrote:
> On 26-Sep-16 08:58 AM, Colin Smale wrote:
> On 2016-09-26 00:17, Warin wrote:
> Perhaps you could state your definition?
> One definition I saw briefly said something about the maximum expected
> area ... I only skimmed it .. looking for a open source map of the
> floodplain (by whatever definition :) ).
> There are some 'floodplains' on the NSW LPI Base Map - available in OSM
> (similar availability to Bing imagery - but has addresses, parks, forests
> etc).
> The flood level in Forbes was supposed to peak at 10.7 metres .. over the
> 'normal' level of the river? Or over the bed of the river? I don't know ..
> but 10.7 is fairly high!
> I don't have my own definition, and I don't want to make up a new one. A
> quick search revealed these:
>    - a nearly flat plain along the course of a stream or river that is
>    naturally subject to flooding.
>    - an area of low, flat land along a stream or river that may flood
>    - an area of land built up from soil left by floods
>    - level land that may be submerged by floodwaters
>    <http://www.merriam-webster.com/dictionary/floodwaters>
>    - a plain built up by stream deposition
> They all sound rather open to interpretation, but they are all based on
> natural phenomena, not government classifications.
> I would expect this to be similar to other OSM 'definitions' like stream
> vs river, monument vs memorial, city vs town vs village .. a bit fuzzy to
> allow for local variations.
> For example in India the definitions of places looks to be swinging to the
> legal/government determined rather than simply population based.
> This is also frequently the case in the UK by the way.
> The distinction between city and town, and between river and stream, is
> cosmetic, and the fuzziness doesn't hurt. The fuzziness is in whether
> something is "big" or "small" and there will always be debates about
> "medium" things. The fuzziness in these examples does not affect where the
> lines are drawn on the map, only the tagging. I don't see how that
> principle would be applied to flood plains where the location of the line
> itself is debatable.
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