[talk-au] Use of DEM data to generate streams

[Adam Steer]

Hi all

I've been doing quite a bit of stream and catchment delineation from lidar
lately for some capability demonstration / bizdev projects / fun
cartography. This next bit is probably preaching to the converted, however
I haven't seen it discussed...

Something to remember is that strahler order often used to make "bigger
streams" is a measure of connectivity rather than importance. Like, a
significant stream can have the same strahler order as a tiny trickle. In
waterwaymap.org, it looks like this happens a bit (sudden jumps in stream
width etc). Having said that I haven't looked into how the widths are
computed.

A possibly obvious contribution is that streams from a 10m DTM will be
different from streams made with a 2m DTM. I also wonder if computing
stream power (or some related metric) might also help? Thinking about
rendering in terms of how much water might come here.

HTH. All sounds great, I just haven't been brave enough to change river
locations in OSM yet!

Cheers,

Adam
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