I delineated flow directions in a watershed on ArcMap (10m DEM). Then I want to calculate distance between two points 'following' the flow direction in each raster cell, not a straight line distance.

Is there any way to do it automatically on ArcMap?

Added description: The below image shows an example distance (black line) that I want to calculate. Those arrows represent a flow direction in each cell (I changed the symbology to show those directions by arrows). The distance is not on a channel.

enter image description here

  • 2
    To answer your question: yes! Please make sure you take the tour and learn about the format we follow here. A good question is expected to show some effort/research on the asker's part. You should end up on this site when everything you've tried has failed, not when you're beginning your process. Can you please elaborate on what you've already done to address the question yourself?
    – jcarlson
    May 22, 2019 at 14:42
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    You would convert your dataset to a network if you want to trace between two points. You could explore using geometric networks/network datasets and automate tracing using modelbuilder or use specialist software such ArcHydro or RivEX.
    – Hornbydd
    May 22, 2019 at 14:52
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    Alternatively sample flow length raster.
    – FelixIP
    May 22, 2019 at 21:17

1 Answer 1


If you have the Spatial Analyst extension, you could use the Flow Length tool to create a flow length raster.

Then calculate the difference between the flow lengths of each pair of points based on which cell of the flow length raster they coincide with. (Of course you would need to be sure that both points in the pair are on the same stream).

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