I have the Basic license for ArcGIS and so I cannot use the collapse dual lines to centreline tool or the river bathymetry toolset by ESSA as they both need an advanced license.

Any idea how I can find the centreline or thalweg of the canyons using another tool which works in the standard version of ArcGIS please?

Canyons Image

  • This answer to an old question may be useful: gis.stackexchange.com/a/579
    – PolyGeo
    Commented Jul 9, 2015 at 10:21
  • In looking at your screenshot full size, it's somewhat clear that the flowline/thalweg (and +1 for teaching me a new word) isn't necessarily the centerline of the polygon boundary - in fact, some of them are quite far from the middle of the polygons. How accurate do you need them to be? How many are there? Manually drawing them based on the contours might be the best approach if you can't use Spatial Analyst hydrology tools (can you clarify not only do you only have Basic, but you don't have any extensions either?).
    – Chris W
    Commented Jul 9, 2015 at 21:27

1 Answer 1


From the look of the screen shot it looks like you have spatial analyst so you could use this approach:

  1. Convert polygons to rasters.
  2. Run the rasters through the Thin tool.
  3. Convert raster skeleton back into a polyline dataset.
  4. Edit as necessary.

You will need to experiment with thin options and certainly do some post thinning editing of the vector lines to remove the spurs\loops that will be generated. As you have a few polygons to deal with then the editing time will be fairly quick. Below is an image of the output of a Thin tool before its converted to a vector line for editing ran on some polygons I have.


If editing sounds too much you could turn the polylines into a network dataset and extract out routes between 2 points which would be the centreline. Just an idea?

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