topic Gaps in watershed boundary delineation using watershed tool in ArcGIS Spatial Analyst Questions

Gaps in watershed boundary delineation using watershed tool

JeremyKiss1 — Tue, 04 Apr 2017 17:17:00 GMT

I am trying to delineate the watershed boundaries for depressions. I created a raster from the depression polygons and used Arc's flow direction tool as inputs in the Spatial Analyst watershed tool. However, there are gaps in the watersheds where there intuitively should not be. I've attached an image of an example. The blue represents the depression polygons, the other colours represent the watershed boundaries, it's underlain by flow direction output. I'm not sure why that whole hill slope is not delineated as a part of the middle depression's watershed.

This is in the prairies so the relief is pretty subtle (this is using vertical exaggeration of 5 in ArcScene). I'm wondering if these gaps are because the flow direction tool uses a D8 flow routing. Any tips?

Re: Gaps in watershed boundary delineation using watershed tool

DanPatterson_Retired — Tue, 04 Apr 2017 17:28:08 GMT

And this is after you ran Sink with the suggestion to use the results to assess sink depth (see how it works ...) which can then be used in the .,..Zonal Fill or the Fill... tools. D8 is obviously highly localized and obviously filling sinks can lead to more sinks that need filling etc.

Re: Gaps in watershed boundary delineation using watershed tool

JeremyKiss1 — Tue, 04 Apr 2017 18:09:25 GMT

This worked, thanks! I needed to define a small enough fill value to maintain the actual depressions.

Cheers,

Jeremy

Re: Gaps in watershed boundary delineation using watershed tool

DanPatterson_Retired — Tue, 04 Apr 2017 18:39:30 GMT

glad it worked