[Tagging] Way inside riverbank

[Malcolm Herring]

This idea of the linear river way being along the deepest part seems to 
have been created in this thread. No such 'rule' exists, either in 
practice, nor in Wiki tagging pages. The normal usage is to place the 
way along the approximate centre line of the waterway, just as we do 
with roads.

As to the direction, this usually can be determined by watching the 
water flow, or simply by knowledge of the surrounding topography. There 
are some problematic cases:

1. Contour canals have no flow. The direction or the way is arbitrary.

2. Canals that pass over summits flow away from the summit reach, so the 
way must be split into two opposing directions at the point of the 
feeder reservoir. Likewise at lowest reach between two summits.

3. River deltas often have channels that cross between two branches of 
the same river. The direction of the way is arbitrary.