Tag:waterway=riverbank
+/- waterway=riverbank
For tagging wide rivers which need to be defined by an area rather than just shown as a linear way.
Used combinations in
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This describes the tagging scheme for large rivers, or sections of a river which are wide enough to "require" mapping of distinct areas of water/river banks. Example: River Thames as it flows through Central London.
For small rivers it is not necessary to draw an area for the riverbank, but it might still be interesting, especially if it is irregular.
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How to Map
The area of the river should be marked by a closed area drawn along the riverbanks, and closed at each end. In practice, as wide rivers tend to be long, the river will be drawn as a series of adjacent closed areas (ways 1 & 3 in image below).
These areas should be tagged as waterway=riverbank, or as natural=water + water=river (water=canal for canals).
In addition a way tagged as waterway=river (way 4 in image below), must be drawn in the direction of the river flow (i.e. from source to sea) along the Thalweg or the deepest points of the riverbed.
Islands
A multipolygon relation should be defined and the island and the main river bank included in the relation. The main riverbank way (way 1 in image below) will have the role 'outer' and the way for the island (way 2 in image below) will have the role 'inner'.
Unification of the island case and normal case with a multipolygon relation
Another way to tag those large rivers is by using Relation:multipolygon. It creates only one relation for the whole river and does not need creating arbitrary cuts along the river. Note however that extremely long member ways or ones with thousands of points cause problems for many data users. In osmarender, ways longer than about 20km run the risk of not being completely loaded into memory during rendering which results in the river "spilling" out of its boundaries.
Tags used are :
- type=multipolygon + waterway=riverbank + name=* + ... for the relation containing ways 1 to 7
- OR using the new proposal : type=multipolygon + natural=water + water=river + name=* + ...
- Members ways 1 to 6 have role outer and way 7 has role inner
- Ways 1 to 6 are tagged waterway=riverbank. Way 7 can have no tag at all or if it is itself something tag it with what it is.
- Direction of ways does not matter
- Original proposal is here : Relations/Proposed/Rivers
Varying water level river
We might aim to mark riverbanks on its high-water extent, including sandbanks. Therefore non-permanent islands (sandbanks) are not included. Only permanent islands are marked.
This is consistent with mapping of natural=coastline which we aim to place at the high-tide level. Rivers can have complicated flood characteristics. We wouldn't map flood plains as part of the large river, unless perhaps they are flood as often as every year, such that nothing gets built there (approximate rule of thumb, open for discussion).
In general these rules can be followed more closely if we have better data (ideally someone living locally observing the river's position) When sketching from imagery, it is acceptable to just do our best based on what we can see (e.g. assume visible sandbanks get washed over as pictured above) Note that you should always be careful to avoid overriding valuable on-the-ground mapping with information sketched from imagery.
Riverbank mapping hint
This describes how to use the "create parallel way" tool in Potlatch 2 to create a riverbank from a river. This method works best when mapping a section of river that has a consistent width and each side of the riverbank is nearly identical in shape.
- Create a waterway=river down the middle of the river
- Select a section of the river that has a consistent width
- Select the parallel tool or type "p"
- Adjust the new parallel way's distance from the original way so the new way is half the width of the river (zooming in helps)
- Create a parallel way on the opposite side of the original river
- Label both new ways identically as waterway=riverbank
- Connect the ends of each new riverbank to create a closed loop
- Use the "merge ways" tool to merge these into a single way representing the riverbank area.
See also
- waterway=river
- natural=water
- water=*
- Relation:waterway
- WikiProject Rivers
- WikiProject Whitewater Maps additional tags for canoe sport
- Proposed features/Tidal Rivers
- Proposed_features/Water_cover
