[Talk-us] Waterway directionality in drainage canals

Alexander Roalter alexander at roalter.it
Sat Apr 28 22:19:44 BST 2012

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 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.


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