I have successfully been using the trace upstream in ArcGIS with 10,000+ points as flags to find what polygons are upstream (using a select of the polygons than intersect the upstream trace).

Now I need to know how far upstream a polygon is. That is, I know which polygons are upstream but I do not know the distance from the flag along the network to the polygon. If I cannot get distances even sequence would do (this is the first poly upstream, this is the second and so on) although distance upstream is preferred.

ArcGIS Geometric solution. I have close to 100,0000 flags (points) in total. Trace upstream works great but now I need to add the distance upstream to each feature.

  • These polygons? Are you actually tracing upstream to a point created by the intersection of the polygon with the network? – Hornbydd Sep 16 '15 at 18:02
  • I am tracing upstream and then extracting polygons via a select. I need to get the distance to these polygons. – If you do not know- just GIS Sep 16 '15 at 18:11
  • So the polygons do intersect the network? – Hornbydd Sep 16 '15 at 18:13

I would start by "reducing" your polygon to a point so its a point snapped to the network with the polygon ID. First problem is which point, what if your polygon intersects the network multiple times and worse still across multiple sub-catchments. You have not described your scenario sufficiently enough. You should edit your question with some pictures.

Assuming best case scenario, that each polygon intersects the network once at their downstream end then you need to automate the searching. This could be done in model builder using the Trace tool. I can tell you now that that will be painfully slow if you are processing over 100K flags. Even once you have done the trace you'll need to clip it back as this returns selected edges. As soon as you start fiddling around with geometries you are better off doing that in python.

If you cannot program in python then it may be worth investigating ArcHydro, it may be able to automate it? I don't know.

RivEX is designed to work with river networks (not geometric networks) and it has the tools that can link points, return their routes and lengths. Have a look at that website and it's help file to understand what it is capable of

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