Proposal:Waterway classification
| waterway classification | |
|---|---|
| Proposal status: | Draft (under way) |
| Proposed by: | Tilia J |
| Tagging: | |
| Applies to: | 
|
| Definition: | More clear definition of waterways and further refinement of waterway classification. |
| Draft started: | 2022-12-08 |
Proposal
A finer and hierarchical classification of natural and artificial waterways, along with refining or redefining individual waterway keys to clarify the differences and interdependencies.
Rationale
The current waterway classification is only on the main waterway key. Lack of a widely accepted subdivision in separate classes or categories prevents proper distinction in properties such as importance, usage, or size relative to other waterways.
Definitions sometimes contradict, have arbitrary or subjective class boundaries or are influenced by local circumstances, legislation, definitions or naming.
This not only prevents correct tagging, but also complicates proper rendering rules for different zoom levels based on well-defined classes and properties.
Tagging
Canals
Canals need to be slightly redefined to emphasize water mangement: Canals or artificial waterways are waterways or engineered channels built for water management (e.g. polders, flood control and irrigation), conveyance of drinking and irrigation water or for transport.
Canal categories
The infrequently used canal=* tag, which currently mixes op values, usage and lifecycle, is to be used for subdiversion in canal categories.
| Key | Value | Element | Description | Rendering | Photo |
|---|---|---|---|---|---|
| canal | marine |
|
Interoceanic canals or canals from sea to inland ports | 
|
_in_the_Suez_canal_1981.jpg)
|
| canal | primary |
|
Waterways of international importance |
|
|
| canal | secondary |
|
Waterways of international or national importance |
|
|
| canal | tertiary |
|
Waterways of regional importance |
|
|
| canal | unclassified |
|
Canals used for discharging of superfluous water, transport, recreation and transmission of irrigation and drinking water |
|
|
| canal | leat |
|
Small, usually less than 5 meters wide watercourses for discharging of superfluous water or local transmission and distribution of drinking and irrigation water as well as water for mills, mining and industries |
|
|
| canal | conduit |
|
Tiny, less than 1 meter wide artificial watercourses for discharging of superfluous water or for local distribution of drinking water and water for irrigation, mining and industries |
|
|
Navigable canal types
- Contour canal
- Summit-level canal
- lateral canal
- Side Slope Canal
Access
Access or navigabity restrictions can be set either by
- General access restrictions for water-based transportation
- Specific size restrictions for inland navigation
- specifying a vessel size class using the ship=* tag with keys such as:
Further subcategorization
canal=unclassified, canal=leat, canal=conduit often have historical / local characteristics with a multitide of types which can be furter specified using:
- canal_alt=* having historical characteristics like:
- Millraces
- Log fumes
- canal_local=* having characteristics that can only be found in particular countries and regions, and therefore have a country-specific prefix:
- uk:Leat (note that "leat" is a general definition as well as common in England and in Wales to designate a type of ancient and historical watercourses.
- nl:spreng
- de:suone
- de:kunstgraben
- pt:levada
- fr:bief
- ma:khettera
Usage
Canal usage=* is to be extended with three values to cover all further identified applications or uses:
tunnel=canal
Ditches and drains
Regarding the discharge of superflous water, natural waterways, canals, ditches and drains are related as follows:
- Apart from discharging water to larger water bodies, canals and ditches are or can be part of a managed water system. By using weirs, dams and sluice gates the water outflow can be:
- regulated or stopped in order to maintain a constant surface water or groundwater level upstream
- regulated in order to maintain a minimum flow or water level downstream
- diverted or discharged to manmade=* basin=retention (overflow) or basin=detention (buffered) to maintain a maximum water level downstream
- conveyed away for use elsewhere
- buffered (hydro-power generation) or stored (drinking water, irrigation or in general for dry periods)
- The only function of drains is to capture and convey water to an basin=infiltration or other larger body. Either via a ditch or directly to a canal or stream.
Ditches
An artificial free flow watercourse used for collecting and discharging superfluous water or is part of a managed water system designed to regulate surface water and groundwater level.
Drains
An artificial free flow watercourse used for catching, collecting and conveying superfluous water like surface runoff or groundwater from a starting location to a retention or detention basin or via an outlet into larger watercourses like ditches or discharce channels.
- Groundwater drainage
- Surface runoff is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil
- Urban runoff (impervious surfaces)
- Lowering the groundwater level for agriculture and land use development
- Rainwater and groundwater harvesting for irrigation and drinking water for humans and livestock
- Erosion control
- Flood control
| Key | Value | Element | Description | Rendering | Photo |
|---|---|---|---|---|---|
| drain | french_ditch |
|
Trench filled with gravel or rock, or both, containing a perforated pipe that redirects surface water and groundwater away from an area | 
|
|
| drain | drainage_ditch |
|
Ditch located alongside roads or in agricultural land and meadows to catch groundwater and surface runoff. On the image a "normal" ditch can be seen in the foreground with drainage ditches in the meadow. |
|
|
| drain | trench |
|
Trough- or channel-shaped body with a solid cover or grating that is flush with the adjoining surface |
|
|
| drain | swale |
|
Shallow channel with gently sloping sides to manage water runoff |
|
|
| drain | slot |
|
Drainage pipe with a thin slot (or neck) that opens at the ground surface with sufficient opening to drain water runoff, does not have any kind of grating. |
|
|
| drain | levee |
|
Surface channel dug on land with a gradient where the removed soil is used to create a levee on the downslope of the channel. |
|
|
| drain | countour_trench |
|
Trench dug along the contour lines of a slope. Doing so stops the water flowing downhill |
|
|
Natural waterways
Only the waterway=stream page defines the distiction between rivers and stream for OSM:
Use waterway=stream for a naturally-forming waterway that is too narrow to be classed as waterway=river (the commonly accepted rule for OpenStreetMap is that a stream can be jumped across by an active, able-bodied person). A stream need not be permanently filled with water. In case of varying size or intermittent waterways the distinction from larger rivers based on the above criterion should be made with respect to the high water level.
This rule prevents many streams that are identified as such in the real world from properly tagged
Therefore the above rule is to be replaced with the following rule of thumb readily found on the internet:
You can step over a brook, jump over a creek, wade across a stream, and swim across a river.
Rivers
A wide, natural watercourse a person can only swim across, that discharges a draining basin and flows to an ocean, sea, lake or another river.
Streams
Changed definition (too shallow) and criterium (cross it without swimming), : A naturally-formed waterway that is too narrow and / or shallow to be classed as a river. An active, able-bodied person should be able to cross it without swimming on most places.
- stream=large Person can ford or wade across on most places
- stream=Small Person can jump or step over
Use stream_local=* to assign local or regional names like:
Examples
Rendering
Features/Pages affected
External discussions
Comments
Please comment on the discussion page.