[talk-au] Streams and dams

[Tom Brennan]

Sounds good.

I'm inclined to go with (1), but (2) could presumably work with a relation?

cheers
Tom
----
Canyoning? try http://ozultimate.com/canyoning
Bushwalking? try http://bushwalkingnsw.com

On 5/06/2023 8:47 am, Little Maps wrote:
> I don’t know if there’s a “correct” method as at least 3 different methods are (or were) common in Vic, where I map. (1) continue named stream through dam, (2) continue stream through dam but with no name tag, and (3) stop stream at dam edge and start again the other side. Method 2 means dam name is rendered but not stream/river as well inside the dam. If the stream/river is in a relation this isn’t a problem as the whole named stream can be found using the relation.
> 
> I prefer continuing the waterway through the dam as it makes it a lot easier to find gaps in waterways and to show connected watersheds, etc. If dams are often dry or rarely full, it also shows where waterway is at low lake levels. Logically, also the Murray River flows through Lake Hume. It doesn’t stop at one side and start again on the other.
> 
> I’ve been editing heaps of streams in Vic over past few months, and it’s common for waterways to cross dams but not actually connect with them. It’s important that they share a node at each place they cross a dam. Lot’s don’t (or didn’t). The same thing applies on the coast, where many streams cross the natural=coastline polygon but don’t connect with it.
> 
> If all streams that connect with the coast connect properly you can easily do an overpass query to find all watersheds that drain into a section of coast. If all streams properly cross and connect with dams, it’s easy to find all streams that enter the Murray - Darling Basin, for example.
> 
> A fine-detail issue on your query below is that, on the ground, streams don’t normally pass over earthen dam walls. If they did the wall would erode. Instead, there’ll be a side route where water will flow beside the dam when the dam is full. Sometimes this can be seen on imagery, often not. IMO this is an issue of mapping scale, and it’s fine to map a stream waterway as passing through a dam. If someone wants to add the fine detail later they can, while still maintaining the connectivity of the waterway.
> 
> So, broadly, yes, I think it’s much better if waterways pass through constructed reservoirs.
> 
> Cheers Ian
> 
>> On 4 Jun 2023, at 9:48 pm, Tom Brennan <website at ozultimate.com> wrote:
>>
>> Quick question on streams and dams/reservoirs.
>>
>> If a stream has been dammed, the centreline of the stream should still be mapped as a waterway. Correct?
>>
>> cheers
>> Tom
>> ----
>> Canyoning? try http://ozultimate.com/canyoning
>> Bushwalking? try http://bushwalkingnsw.com
>>
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