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I there a way of calculating only the flowaccumulation which are generated in the yellow area and assigning this calculated value to the related end of the stream which is entering the river?

  • red cells represent my linear stream network
  • blue cells represent the river
  • black arrows mark the entering points

stream network in Landuse

I´m using ArcGIS 10.2.

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Using a weight grid in the flow accumulation procedure should get you there. Use the raster calculator (or the Con or reclassify tools) to create a weight raster where the yellow zone equals 1 and other zones equal 0.

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  • Thanks for the hint but I´m not sure how this works. I tried it in my model and in the first moment it did what I wanted but when the flowaccumulation leaves the yellow areas it gains more cells although the weight raster has the value 0. Why is this happening and how can I avoid this? – Max2603 Sep 8 '16 at 10:11
  • Are you sure that it's actually gaining cells outside the yellow area or just maintaining the upstream accumulated value? – Jae Sep 8 '16 at 10:13
  • Remember to still think of the underlying watershed. If there is an area in yellow which would flow downstream towards your downstream outlet, those values will still be accumulated even if there is a "0 weight" area (like your light green area) in between. If you need to completely ignore areas, consider setting the areas to NoData using SetNull. – Jae Sep 8 '16 at 10:32

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