I have DTM for quite small area (400x200 meters) which was interpolated from elevation points. I want to create raster which will show water stream (not arrows but basically slope and river flow map - output from Flow Length would be enough). My DTM looks correct.

I use Fill to fill gaps and then Flow direction, where the problem occurs as you see below. For some reason there are created these straight lines which then also influence the Flow Length output. Please do someone know where is the problem and how to avoid it? Maybe the problem is that the DTM was created by interpolation, the area is to small or that there is small "lake" in the middle. enter image description here

1 Answer 1


Try to look at this question and answers for more information about ArcGIS and GRASS GIS hydrology: Methodology for creating accurate drainage networks (and catchments) from high resolution LiDAR DEM?.

  • Thank you for hint. It looks problem will be with the high resolution/small area combination. Still don't know how to do it correctly, but r.stream.extract makes best results so far, at least until I'll find better solution.
    – daky
    Commented Aug 19, 2020 at 9:23

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