[Talk-us] Waterway directionality in drainage canals

Paul Norman penorman at mac.com
Sat Apr 28 20:23:23 BST 2012


> From: Nathan Edgars II [mailto:neroute2 at gmail.com]
> Sent: Saturday, April 28, 2012 2:24 AM
> To: Tag discussion, strategy and related tools; OpenStreetMap talk-us
> list
> Subject: [Talk-us] Waterway directionality in drainage canals
> 
> It's the standard to draw a waterway in the direction of flow. I've
> questioned this several times, but it's an ingrained default.
> 
> My question is more specific: what happens to a drainage canal that
> reverses direction? I offer the Everglades and surrounding agricultural
> land as an example. There are huge "water conservation areas" that store
> water. When it rains, gates are closed and opened to direct water into
> these. During a drought, gates send water back out into the canals for
> local use. When there's a big storm, water will instead go directly out
> to sea.
> 
> So there are a lot of major canals that have no fixed direction. How
> should these be mapped? Is there any existing scheme that can show how
> water flows under different conditions?

The same issue came up with minor drainage ditches and cranberry fields
here. They're used to drain sometimes and sometimes to flood the field for
harvest.

I came up with the proposal
http://wiki.openstreetmap.org/wiki/Proposed_features/directional for
directional=* but it's abandoned. 

One weakness with the proposal is that unknown values are a special case of
directional=no, not directional=yes




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