I'm pretty new to the Arc Hydro Toolbox.

I used assign stream slope in the Arc Hydro toolbox. It produced a mostly correct to and from elevation. However, if you look at the purple arrow, it shows a mistake. That river goes from low elevation to high and then back down to low (the highlighted main river channel is low again). It does it again at other locations above the purple circle.

Any suggestions on how to fix this? Are there any issues with a river line file that could trip up the tool?

Purple arrow shows one issue with the elevation assigned

1 Answer 1


When you are using Archydro, You must consider some important topology and spatial rules.

I listed some of them but not all. You can find comprehensive rules in this document.

  1. stream direction (flow direction) is a critical factor. Maybe you need to flip the direction.
  2. The streams must be intersected at junctions
  3. Must not overlap
  4. Spatial or temporal issues with DEM and (or) Stream layer.

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