Adjust flow direction in streams

[AlexanderVentura]

Hi all,

I am processing a terrain following the ESRI manual "Overview of Arc Hydro Terrain Preprocessing Workflows". More specifically I'm using case 8: Completely dendritic terrain with known stream locations (using synthetic streams).

I have a stream feature class that I first pass through "Create Drainage Line Structures" (as specified in the manual). I then fill sinks and run "DEM reconditioning from stream grid" using the stream grid created in the previous process. 

From here I simply follow the manual (case 8 as I specified above).

What I noticed is that in comparison to case 9 (Completely dendritic terrain with known stream locations (using user specified streams)) in case 8 it is not needed Adjust Flow Direction in Streams.

Could someone please confirm this is correct and possibly explain why this is the case?

Thanks so much.

Alex.

[ChristineDartiguenave]

Synthetic streams are derived from the flow direction. They will always be oriented in the direction of the flows and their direction will match the direction of the underlying DEM.

The direction of user specified streams may not match the direction of flows based on DEM in flat areas. So we need to adjust the direction in the flow direction grid to enforce the direction in the direction of the streams.

Christine Dartiguenave

Esri Water Resources Team