topic Why do the pour points shift? in Water Resources Questions

Why do the pour points shift?

DaveSimpson — Tue, 07 Jul 2015 21:19:57 GMT

I am using the online watershed tool to identify watersheds. It works great, but my pour points are shifted from where I selected. Why do the pour points shift, am I missing something?

Re: Why do the pour points shift?

IanMurray — Tue, 07 Jul 2015 21:25:59 GMT

Could you be a little more specific about what online tool you are using? A link would be helpful....

Re: Why do the pour points shift?

DaveSimpson — Tue, 07 Jul 2015 21:48:36 GMT

Sorry, it is the arcgis on hydro.arcgis,com tool. See screenshot below. You can see the offset of the pour points in the lower left.

Re: Why do the pour points shift?

DanielStauning — Tue, 07 Jul 2015 21:59:31 GMT

Dave,

I would explore the snap distance parameters in the tool, here is the documentation: It should snap to the cell of highest accumulated flow and move the pour point to that location.

Watershed—ArcGIS REST API: Elevation Analysis services | ArcGIS for Developers

Thanks,

-Dan

Re: Why do the pour points shift?

SepheFox — Tue, 07 Jul 2015 22:07:25 GMT

I'm guessing it's because you have the Return Snapped Pour Points box checked.

Re: Why do the pour points shift?

SepheFox — Tue, 07 Jul 2015 22:11:17 GMT

To be more specific, "The service will move points to be optimally located relative to the flows in the elevation model if they are not already there." You want the pour points to be on the nearest point of highest floe, or you will end up with tiny little watersheds.

Re: Why do the pour points shift?

DaveSimpson — Tue, 07 Jul 2015 22:26:39 GMT

OK, I figured it out. I used a snap distance of 30 which is the resolution of the data source I selected.