I would like to create a map showing the results of watershed analysis as well as the resulting stream network with flow direction.

I have a stream network which has been created from the flow accumulation raster. I also have a stream link raster which was created from the resulting stream network raster and the flow direction raster.

Once I convert the stream network or the stream links to vector polylines the resulting feature class does not retain the correct directions of the various segments.

What is the approach?

I have ArcGIS 10.2.1 Standard, Spatial Analyst, 3D Analyst

Red lines on the below example show the network I would like to show the map along with arrows indicating direction of flow:
enter image description here

  • The method that I employ is to get the elevation of both ends and find the lines where the from elevation is lower than the to elevation and reverse direction. This can mostly be done with geoprocessing but reversing line direction is not something that there is a tool for (that I know of). Would you be comfortable with python or even better ArcObjects? – Michael Stimson Jun 17 '14 at 22:08
  • 1
    How did you convert the stream network raster to vector? The Stream to Feature tool seems to imply that it would also take your flow direction raster as an input to ensure the vector lines flow the correct way. Did you use a different tool, or did this tool not work correctly? – Chris W Jun 17 '14 at 22:27
  • That's it @Chris! Totally forgot about this. I simply converted raster to feature. Please add this bit to your answer. – Jakub Sisak GeoGraphics Jun 18 '14 at 2:19
  • Jakub - done. @MichaelMiles-Stimson just in case, there is in fact a GP tool to reverse line direction in addition to the ability to do it while manually editing - links in my answer. – Chris W Jun 18 '14 at 3:29
  • 1
    Nice script @StephenLead! – Jakub Sisak GeoGraphics Jun 18 '14 at 12:58

I can think of a few ways to do this:

  • Symbolize the lines so they have direction indicated, and manually Flip those in the wrong direction.
  • Use an attribute if available or a calculation (such as end z > start z) to select segments going the wrong direction and Flip (GP) them.
  • Create a geometric network of the lines and use the Flow Direction tools, setting appropriate sinks and sources.

However the best solution might be not having to do it at all. Using the Stream to Feature tool should allow you to use both your stream network raster and your flow direction raster as inputs so that the vector stream lines that are output have the correct direction to start with.

  • Additionally, ArcHydro Tools has got functions to create stream lines from flow direction grids etc., which will be oriented in a useful way. The package also provides a bit more control than the standard tools in Arcmap. – Martin Jun 18 '14 at 6:12

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.