Proposal:Water bodies
| Water bodies | |
|---|---|
| Proposal status: | Inactive (inactive) |
| Proposed by: | Pshunter |
| Tagging: | water=* |
| Applies to: | relation 
|
| Definition: | General tagging of water bodies |
| Statistics: |
|
| Rendered as: | Blue, various |
| Draft started: | 2009-02-19 |
| Proposed on: | 2009-02-19 |
Note: parts of this proposal may be obsolete, because this proposal predates Key:water (see also: its approved “Water Details” proposal).
This is a work in progress. If you have suggestions you can help either directly or in the discussion page.
Rationale
There are scattered efforts to improve how water bodies are represented in the database. For now we have the waterway and some of the natural tags.
Discussed issues cover :
- Riverbanks and islands in the middle of rivers Relations/Proposed/Rivers
- Bodies with variable water height Proposed_features/Water_cover Proposed_features/Intermittent_Lake
- Large lakes Proposed_features/lakeshore
- Wetlands natural=wetland cover aspects of vegetation in wet areas.
- Flood plains Proposed_features/floodplain with the associated risk levels of a potential flood
There is no specific tag for wadis, ponds, oasis, waterfalls Proposed_features/Waterfall, underground rivers or lakes, probably more…
This proposal aims to regroup and support all these features in a coherent manner.
Tagging
A complete water limit is the contour of water at a specific height. If the limit is too long or contains holes individual ways can be collected into a multipolygon relation. Otherwise a single way is used as is. A complete water limit accepts the following tags :
Existing tags
| key | values | meaning | use with |
|---|---|---|---|
| natural | water,wetland | ||
| wetland | grass, trees, mangrove,… |
New proposed tags
| key | values | meaning | use with |
|---|---|---|---|
| water | river, lake, lake, pond, saltylake, sea,… | Used to differentiate features semantically. | water=* |
| bank | sand, rocks, gravel, concrete, urban, trees… | this kind of surface is to be expected on the banks (outside) of the area delimited by that way. Maybe make provisions to specify different surfaces on the right and left bank for linear features. | water=* ; waterway=river,stream ; natural=wetland ; standalone |
| dry_surface | sand, rocks, gravel, concrete… | Surface when there is no water. Only useful if the distance between two water limits is very large. | |
| extent | permanent,high,low,mean,flood,changing,… | Explains what type of water limit this way denotes. High marks the position of water when the water is high. | water=* ; waterway=river,stream ; natural=wetland ; standalone |
| when (or oftness) | season, tide, intermittent, exceptional,… | indicates on which occasions the level is reached | water=* ; waterway=river,stream ; natural=wetland ; standalone |
| sail | yes,no (default depends on particular feature) | indicates that you can sail on the water when it is at this level | water=* ; waterway=river,stream ; natural=wetland ; standalone |
The most significant feature will be tagged with the relevant tags above.
The alternate water levels will be tagged only with bank=*, extent=*, when=* or sail=*
Then, a relation is used to link the alternate levels to the most significant one:
| key/role | values | meaning | use with |
|---|---|---|---|
| type | water_regime | ||
| core | [most significant feature] | ||
| alternate_regime | [alternate regimes]* |
If the alternate regime is already using a relation (multipolygon) because of its size or its complexity, simply reuse that relation and put the related core feature in rhe core role.
Explanation of key values
| key | value | meaning | rendering | example picture |
|---|---|---|---|---|
| bank | sand | |||
| bank | rocks | |||
| bank | gravel | |||
| bank | salt | |||
| bank | mud | |||
| extent,when | permanent | The water level does not change. This is the default value and should not be specified. | solid blue | |
| extent | high | The water raises to that level on highwater events | intermingle '+' symbols with the dashes from the when key / area hashed blue | |
| extent | low | The water lowers to that level on lowwater events | intermingle '∣' symbols with the dashes from the when key | |
| extent | mean | The water is usually at that level. To be used on features with non-exceptional variable regimes. | solid blue | |
| extent | flood | The water can reach that level on flood events | intermingle '++' symbols with the dashes from the when key | |
| extent | changing | When the water is at lower levels, it flows through random paths. | Very thin crisscrossing lines along the mean feature path. | 
|
| when | season | The level is reached at particular moments of the year | ||
| when | tide | The level changes in accordance to tidal cycles | ||
| when | exceptional | The level is reached on exceptional events (floods, storms) | dotted blue | |
| when | controlled | The level is reached due to human control (e.g. because of a dam) | long blue dashes which indicate the map user should look for additional info. | |
| when | intermittent | The level is reached on unpredictable events such as rain | dashed blue | |
| when | periodical | The level is reached on regular or predictable events. | long blue dashes which indicate the map user should look for additional info. |
Interaction between extent and when tags
These two tags have some level of dependency, and defining two sets of orthogonal rendering schemes will probably make the map too complicated. Below are some rendering suggestions based on value combinations
| extent=(unspecified) | extent=low | extent=mean | extent=high | extent=flood [3] | extent=changing | |
| when=(unspecified) | solid stroke / solid fill | X | solid stroke / solid fill | X | X | very thin criscrossing blue lines |
| when=season | [2] | long dashes [1] | X | long dashes / light fill or hash | dotted | |
| when=tide | [2] | dotted [1] | X | dashed darker stroke / light fill or hash | dotted | |
| when=exceptional | [2] | dotted white [1] | X | dotted / light fill or hash | dotted | |
| when=controlled | [2] | long dashes [1] | X | long dashes / light fill or hash | long dashes | |
| when=intermittent | [2] | ?? | X | dashed / light fill or hash | X [4] | |
| when=periodical | [2] | long dashes [1] | X | long dashes / light fill or hash | long dashes |
[1] The lowness should be recognisable thanks to the background of the corresponding mean regime.
[2] Same as extent=high
[3] Flood characteristic is recognised because it doesn’t lie against any particular background. Care must be taken not to mistake this with linear features al lower scale. Multiple flood lines can be used, with the date of the maximal event drawn aside the limit.
[4] There should not be no such thing as intermittent floods. Either use highwater extent or exceptional oftenness.
See also
- Proposed_features/Water_details - Approved proposal