I tried to search other questions to see if this has been answered but couldn't find anything, so sorry if this is redundant. I use the Hydrology toolset in Spatial Analyst to create a stream feature in ArcMap using a downloaded DEM. The series of tools I used was the following:

  1. Fill (input DEM)
  2. Flow Direction (input Fill)
  3. Flow Accumulation (input Flow Direction)
  4. Conditional > Con (input Flow Accum – input cond raster, Flow Dir input true rast & the optional)
  5. Stream Order (input Con and Flow Dir)
  6. Stream to feature (input Stream order & Flow Dir) a. Definition query: "GRID_CODE" > 2

I am relatively happy with the outcome except in the north section of the watershed where the stream vector detail was not read correctly and only produced straight lines.

Am I missing a step that would allow this to be read properly and converted into the same level of stream detail as everywhere else in the watershed?

Generated streams with DEM

Note: The straight lines are over cropfields, residences, and timber. I included the only waterbodies on the maps because I did notice on other stream generations that open water creates "straight lines." See aerial image below.

Generated streams over aerial imagery

  • 2
    Those straight lines could be in a lake or a very flay area of your DEM, then you would expect these "straight rivers".
    – Hornbydd
    Commented Oct 9, 2019 at 17:54
  • It looks like the straight lines may be an artifact of your original DEM. Do these lines follow the pattern seen in the flow accumulation?
    – khafen
    Commented Oct 9, 2019 at 17:55
  • 1
    @Hornbydd I noticed that one some other streams I generated but that is not the case here, in both images the only existing waterbodies is shown. I added another close up picture of the aerial with the stream feature to show it is mostly crops where the straight lines are. Commented Oct 10, 2019 at 13:24
  • @khafen The lines do follow the pattern generated in flow accumulation. Does that mean there is no way to fix it? Commented Oct 10, 2019 at 13:26
  • 1
    @Hornbydd many thanks for pointer. TauDEM is totally brilliant set of tools. a) it produces much better looking results b) does it fast by using multiprocessing.
    – FelixIP
    Commented Oct 14, 2019 at 23:08

2 Answers 2


Picture below shows talweg, generated by using flood depth and flow paths derived by using Hydrology tools:

enter image description here

As one can see flow paths depict channel shape in a well defined valleys without depressions along it. If there is one, results are random.

What is happening on a flat terrain is absolutely out of control, your pictures illustrate this nicely. So in order to get something close to reality you have to invest a lot into DEM pre-processing, e.g. burning some major waterways into it.


SOLUTION: I used TauDEM to correct the stream network using the DEM. Below are my results. It is still not exact but it is a huge improvement and definitely usable for my work. Here is a link to a useful guide for anyone using TauDEM for their first time: http://hydrology.usu.edu/taudem/taudem5/TauDEM51GettingStartedGuide.pdf

enter image description here

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