First, I created a flow_direction from a DEM, then I applied corrections to this flow direction. Now my question, how to create a flow network (order flow) from a flow direction, that I already corrected? What tool to use on ARC GIS: ArcToolbox > Spatial Analyst Tools> Hydrology> ....

1 Answer 1


There are a few more steps steps you must take.

  1. Use the Flow Accumulation (Spatial Analyst > Hydrology tools) tool to create a flow accumulation grid.
  2. Create a stream network using the raster calculator tool (Spatial Analyst > Map Algebra). You should enter a funtion like:

    SetNull("[Flow Accumulation Grid]<[flow accumulation threshold],1)

[brackets] should be substituted with appropriate variables.

You now have a stream network raster. You can use additional tools like Stream Link, Stream Order, and Stream to Feature (all under Spatial Analyst > Hydrology tools) to refine your results.

  • Thank you Scott La Vanne for your answer, but I'm stuck in the second step, each time, it makes me an error message!! I use the following formula : SetNull("FlowAcc" < 100,1) what is the problem that may be encountered
    – tazrart
    Apr 18, 2016 at 15:24
  • What is the error message? Apr 20, 2016 at 13:07

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