[Talk-us] Waterway directionality in drainage canals

Dale Puch dale.puch at gmail.com
Mon Apr 30 01:13:28 BST 2012

I would start with the direction as flowing from the spring/rainfall
source, then add the oneway=no as suggested.  This gives a nominal
source-destination flow, even if it is later modified by conditions
(manmade or natural)

A clearer example is a tidal basin.  The normal flow will be out to sea,
but due to tides will also flow in reverse.

On Sat, Apr 28, 2012 at 5:19 PM, Alexander Roalter <alexander at roalter.it>wrote:

> On 04/28/2012 09:23 PM, Paul Norman wrote:
>> 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<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
> How about the oneway property? That is already often used on rivers (not
> so often on streams), but an explicit "oneway=no" would specify that water
> may flow in both directions... Just an idea.
> --
> Cheers,
> Alex
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Dale Puch
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