[Tagging] Definition of lake/pond as applied to stream/plunge pools

[Kevin Kenny]

On Wed, Dec 23, 2020 at 1:25 PM Paul Allen <pla16021 at gmail.com> wrote:

> On Wed, 23 Dec 2020 at 18:04, Brian M. Sperlongano <zelonewolf at gmail.com>
> wrote:
>
>>   I also note that the distinction (effectively) between stream/river
>> (the only variants that are in serious use) is that a stream is small
>> enough that it's modeled by a way, while a river is large enough to require
>> drawing a polygon.
>>
>
> Erm, nope.  The distinction is whether or not you can jump across it.
> However,
> wider rivers may benefit from a polygon.  But if you're in a hurry, or
> can't
> be bothered, don't use a polygon.
>

Surely the text on the Wiki agrees with Paul.

Nevertheless, the illustrative picture accompanying it
https://wiki.openstreetmap.org/wiki/File:Stream_on_Heaphy_Track.jpg shows a
`waterway=stream` that appears to be wider than I'd try to jump. There's
nowhere to get a running start, and I'd probably break an ankle in that
talus.  (Scale isn't quite obvious, but it looks to be about 3m wide
everywhere but the chute in the center of the picture.)  I could probably
step across the chute, but it looks awfully slippery, It's hard to tell,
but it looks as if there are usable 'rock hops' in the slack water both up-
and downstream.  I'm still fine with 'waterway=stream' for a relatively
small watercourse like this one, but 'narrow enough for a reasonably fit
person to leap across' appears to be rather narrower than what people are
tagging in practice - even in Wiki examples!

I wouldn't say that 'rock hop' -> 'stream' is a reasonable implication,
either.   https://www.flickr.com/photos/ke9tv/15541158892 is borderline.
The guidebook calls it a rock hop but I wiped out at it.
https://www.flickr.com/photos/ke9tv/15354148788 is borderline as well. It's
wider,  but considerably more graded and with careful picking of steps I
was able to cross dryshod, despite the bridge being out.
https://www.flickr.com/photos/ke9tv/14711524474/in/album-72157645422380810/
was taken at seasonal low water. You can see from the erosion  on the banks
how much more water flows down it in a wetter season.  I mightn't trouble
to map a riverbank, but that one's crossing over into 'river.'

With the rate of flow and steepness of gradient, I'd certainly not advise
anyone to leap, or even rock hop,
https://www.flickr.com/photos/ke9tv/15537619351, however narrow it is -
it'll pound you on the rocks all down that cascade.  (There's an
established portage route to get canoes around that rapid.) I'd call it a
river, and indeed I'd map the bank when it isn't pounding through a rock
chute - it's pretty wide in the more graded section.
https://www.flickr.com/photos/ke9tv/15540324875 is a tributary upstream of
that rapid.

https://www.flickr.com/photos/ke9tv/21811867291 I would definitely call a
river because (a) I intend to map the riverbank, it's 30-50m wide, and (b)
my party was able to cross at a time of extreme drought.  At a more normal
water flow, that ford is knee- to waist-deep. The fact that you can step
from rock to rock all the way across is no guarantee that it's a stream.
(And actually, I wound up with wet feet because I'm a klutz.)

I've had one German solemnly assure me that anything labeled a 'creek' in
English is a minor watercourse, and challenge why I was mapping a riverbank
for Schoharie Creek. Around here, 'creek' (or the archaic Dutch, 'kill')
appears to be used for any third-order river, whether a trickle or a
torrent.
https://en.wikipedia.org/wiki/Schoharie_Reservoir#/media/File:Gilboa_Dam.jpg
is one picture of a dam on the Schoharie Creek.  I don't think that a
watercourse that supports that kind of hydropower and drinking-water
facility deserves anything other than `river`. Where to transition it from
'stream' to 'river' is pretty subjective. I have indeed jumped across it
near its headwaters.  https://www.flickr.com/photos/ke9tv/9438773781

I don't apologize much for being subjective here.  "Narrow enough for a fit
person to jump" is subject to an assessment of difficulty jumping, an
assessment whether the jumper is fit, and the jumper's own risk tolerance.
'Objectively verifiable' seems to be off on the opposite bank somewhere.

And frankly, I think that's all right. I'm not obsessive enough to haggle
over where the stream ends and the river begins.

-- 
73 de ke9tv/2, Kevin
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