Generate sub-basins according to Strahler order?

Question

Is it possible to generate sub-basins according to strahler order?

Using the watershed function with a stream order stream network results in generating a sub-basin for each stream segment rather than the merged/hierarchical arrangements of catchments you would expect e.g., order 3 basins contain order 2 basins, order 2 basins have order 1 etc

I bet these is really simple and I'm just missing something really obvious.

Cheers,

Simon

SimonAiken · Answer

Thanks mate. I was thinking if I could automatically delineate either stream confluences or pourpoints and extract the stream order values to those points it would be pretty simply to determine sub basins. Hec GeoHMS has a option to 'split at confluences' but you need to manually add the confluences which kinda defeats the point.

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curtvprice · Answer

Using the watershed function with a stream order stream network results in generating a sub-basin for each stream segment rather than the merged/hierarchical arrangements of catchments you would expect e.g., order 3 basins contain order 2 basins, order 2 basins have order 1 etc

Raster datasets do not support overlapping zones, so the Watershed tool simply can't do this.

You could use the Stream Link function to create unique segments, run watersheds one by one, convert each to polygon, and then merge the results. You could tag the orders by doing a Combine of the Stream Link output with the Strahler stream order grid.

Perhaps the ArcHydro tools may be a good approach for you, they create what are called "adjoint catchments" which I think is what you're after.