I am interested in calculating the minimum distance of a canal necessary to irrigate any given point in a map. The problem is that the cost map would have to be asymmetric since water can flow down a slope but not up.

Is there any way of modifying the Cost Distance Tool to allow for asymmetric costs (more expensive to go from "A" to "B" than from "B" to "A"?

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    What software are you using Andrea? Tell a bit more about your data and what tools and steps you have tried so far. – Mattropolis Apr 5 at 0:39
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    It's path distance tool you need, because it has vertical factor, where you can specify negative slopes only and even exclude very steep ones. – FelixIP Apr 5 at 2:55

I used path distance backlink tool plus elevation model in vertical factor. In vertical factor I used binary function to set slopes > 0 and slopes <-30 degrees as no go.

Picture below shows areas reachable from canal plus routes to 30 random points:

enter image description here

  • Thanks! I thought path distance just corrected for the longer path due to elevation changes! I have about thirty other things I could apply this to! – Andrea Apr 5 at 17:17
  • Note that 'table' option in vertical factor is the most flexible one, e.g. gis.stackexchange.com/questions/190144/… – FelixIP Apr 6 at 5:10

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