topic Snap Pour Processing Issue in ArcGIS Spatial Analyst Questions

Snap Pour Processing Issue

DougHaller1 — Thu, 06 Dec 2018 21:03:53 GMT

Can anyone take a look at the workflow I am using, see screenshot of Results and TOC, and explain why I cannot get past the Snap Pour step as explained by esri on the following page...How To: Create a watershed model using the Hydrology toolset

I can create fill, flow direction, flow accumulation layers/shapefiles but I cannot complete the watershed steps because Snap Pour never completes processing.

See attached image.

Re: Snap Pour Processing Issue

ChrisDonohue__GISP — Thu, 06 Dec 2018 21:31:01 GMT

I don't know the exact reason why the tool failed, but I wanted to suggest some options as these sometimes remedy the issue of raster processing tools not working.

I can't tell how your data is structured from the screenshot, but if it is not already, try to place it all in a simple folder on your C: drive before running raster processes. Networked drives can be problematic when processing raster data for a whole host of reasons, so this may remedy the issue.
In terms of simplicity, a folder name like C:/process or something likewise very short is best. Very short both in terms of file path and very short in terms of folder names.
Speaking of short, even though the tools don't explicitly require this, keep all your raster file names 9 characters or less. Some raster processes still seem to adhere to the older raster processing limits (like Grid Stack) even though we are in modern times. Don't ask me why, but sometimes just making raster file names 9 characters or less will suddenly allow the processing to occur. Output raster formats and names—ArcGIS Help | ArcGIS Desktop

Yes, it will be a pain to move all your data around to do this, but it can be worth it to avoid the aggravation of raster tools that go awry for no apparent reason. Move the data to the C: drive, then process it, then move it back to where it will be stored long-term (and rename as needed).

Chris Donohue, GISP

Re: Snap Pour Processing Issue

ChrisDonohue__GISP — Thu, 06 Dec 2018 21:49:25 GMT

Another possibility - the Flow Accumulation step often results in an output raster with values for almost every cell. Since the Snap Pour Point process will evaluate every cell that is not null, sometimes it can be worthwhile to create an intermediate raster to use with all cells below a threshold set to NULL to make the Snap Pour Point process faster. To do this, one could use could use the Conditional Tools CON or SETNULL to set all values below a threshold to NULL.

Con—Help | ArcGIS for Desktop

Set Null—Help | ArcGIS for Desktop

Raster Calculator—Help | ArcGIS for Desktop

Chris Donohue, GISP