topic Re: Create a network of polyline from a flow accumulation raster in ArcGIS Spatial Analyst Questions

Create a network of polyline from a flow accumulation raster

JosselineLou — Thu, 10 Oct 2013 13:23:50 GMT

Hello, I have a problem,
I've created a flow accumulation raster from a flow direction raster (created from an elevation raster).
But now I need to create a polyline feature of the channels but the Stream to Feature tools doesn't crash as I tried to process it.
I'm kind of stuck here, thanks in advance,

Joss

Re: Create a network of polyline from a flow accumulation raster

JimCousins — Thu, 10 Oct 2013 14:07:15 GMT

Try using the raster calculator with a conditional statement and a threshold of accumulation. THis is outlined in the help under Hydrologic analysis sample applications, step 5-6.
Regards,
Jim

Re: Create a network of polyline from a flow accumulation raster

NeilAyres — Fri, 11 Oct 2013 07:07:47 GMT

And as an additional tip when it comes to extracting stream lines from dem's...
I always create a curvature surface and use that as a weighting into the flow accumulation step.
Because of the math of the curvature function, upwardly concave areas (like a stream) are negative,
so invert the curvature output first, (X -1) so that +ve values are associated with upwardly concave areas
and -ve values indicate the top of the hill (for example).

This idea comes from a paper by Tarboten & Ames from about 1992.

Otherwise follow the steps in the hydrology section of the help files as suggested by Jim.

Cheers,
Neil

Re: Create a network of polyline from a flow accumulation raster

JosselineLou — Mon, 14 Oct 2013 07:10:26 GMT

Thanks, the Raster Calculator worked like a charm !

And as an additional tip when it comes to extracting stream lines from dem's...
I always create a curvature surface and use that as a weighting into the flow accumulation step.
Because of the math of the curvature function, upwardly concave areas (like a stream) are negative,
so invert the curvature output first, (X -1) so that +ve values are associated with upwardly concave areas
and -ve values indicate the top of the hill (for example).

This idea comes from a paper by Tarboten & Ames from about 1992.

Otherwise follow the steps in the hydrology section of the help files as suggested by Jim.

Cheers,
Neil

Thank you for your answer first,
but as I'm french, I didn't really understood, do you mean using the Curvature tool in 3D Analyst ?
What are +ve and -ve values ?
Thanks

Regards,
Joss

Re: Create a network of polyline from a flow accumulation raster

MarkBoucher — Mon, 14 Oct 2013 16:38:53 GMT

The Arc Hydro tools will create a network of polylines for the drainage lines (polylines) in a watershed.