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I have flow lines for streams. I've made them into a geometric network. The streams intersect with a rail network. I want to find all of the points of intersection and then get all of the flow lines 30 miles downstream of those points. The idea is to be able to mitigate any hazardous waste spill from the rail. We think 30 miles downstream is a good starting point for planning. How can I create a layer for all of these 30 mi downstream segments? I have included an example of what we're hoping the final product will look like. The rail is the black line and the streams are the blue lines.

enter image description here

  • Number of 30 m points is equal to number of intersection points. Which one is yours? – FelixIP Jun 16 '19 at 20:26
  • I think some of the streams will flow into bigger streams. This means that the number of 30 mi points may be less than the number of intersection points. – Chris Jun 16 '19 at 23:07
  • @FelixIP perhaps there was a misunderstanding about this comment. I didn't understand what you meant by "which one is yours?" I assumed you were asking if I thought my data had equal intersection points and endpoints. I was answering your question by saying I think they won't be equal. I was not trying to refute your point. – Chris Jun 17 '19 at 4:32
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You are wrong with your assumptions.

Picture below shows streams network, where some of the nodes (that I called Railway Intersections) are labelled by their flow distance to outlet. I created 4 "long rivers" starting at these nodes and ending at common outlet. I split four resulting rivers at the same distance of 3700 m from river start, and remove downstream bits. Ends of remaining same length "rivers" shown as red circles. I leave it to you to define pairs of rail intersections/red circles.

enter image description here

So your question needs re-wording at least. Also I used networkx python model to do the job. I don't think you can handle it using standard set of tools, perhaps invest in coding.

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  • Thanks for the example. I can code in Python. Would you possibly share the code that has allowed you to do this? Also, my assumption was that the shared portion of the streams delineated by the upper three endpoints would be captured by the fourth endpoint. – Chris Jun 17 '19 at 3:48
  • The workflow described in my answer. I am not going to post a code, because it's a set of scripts handling network tasks. Your objective is to find lowest of possible points, i.e. travel distance at least 30 mi, or upper most - multiple points possible on many segments. – FelixIP Jun 17 '19 at 4:17
  • I have flow lines for streams. I've made them into a geometric network. The streams intersect with a rail network. I want to find all of the points of intersection and then get all of the flow lines 30 miles downstream of those points. The idea is to be able to mitigate any hazardous waste spill from the rail. We think 30 miles downstream is a good starting point for planning. Does that help at all? – Chris Jun 17 '19 at 4:57
  • Plural for points makes a difference. You can trace one line per stream system from source node closest to common outlet. – FelixIP Jun 17 '19 at 5:38
  • I'll likely have many hundreds of intersection points. It sounds like this cannot be done through ArcGIS then. Is that right? You'd recommend I investigate networkx? – Chris Jun 17 '19 at 5:46

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