On 19/08/18 04:01, Martin Koppenhoefer wrote:
sent from a phone
On 17. Aug 2018, at 13:43, Christoph Hormann <o...@imagico.de> wrote:
If you want to map the river width tag width=*, if you don't want to map
the width then don't create classes based on width thresholds.
river size is not about width alone, the most generic approach to measure size
is looking at the quantity of water per time. It accounts for width, depth,
flow speed in one parameter. For the significance, length is probably also
interesting.
The width alone depends on factors like the terrain and its geology.
These numbers are most useful in relation to other waterways nearby. The
context matters, the same amount of water in one area might be a stream and in
another a river.
Usually at the confluence the name of the waterway with the most water is the
one whose name prevails, but sometimes there are exceptions, e.g. for historic
reasons (e.g. they didn’t know exactly which river brought more water, or
considered one more important for other reasons)
For navigation it is interesting to know if you can cross the waterway without
bridge, tunnel or ford by jumping over it (width) or by walking through it
(depth).
Of course there are exceptions.
The Todd River in Alice Spring Australia has had 0 width and 0 flow every time
I have been there.
And you can walk across it, camp in it .. play games in it. Most of the time.
Yet it is a river as can be seen by the width of the sandy river bed and the
length of the bridges crossing it.
And when water does flow in it you don't want to be in it .. even in a boat.
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