I am trying to run ArcGIS 10.1 flow accumulation on a 10000 x 10000 cell unsigned 8Bit integer flow model (but 80% of that is no data). The data has been through a "fill" procedure once.

The only unusual aspect is that I have inverted the DEM, so the water flows from 0 into negative values.. could be an issue??

The model has been running for 24 hours, but while ArcGIS claims it is processing, the GPU shows no activity and the output file is empty.

My machine is a 2Ghz quadcore, 64 bit Win7 OS. How long might I expect this to run, and is there anyway to tell if it is working at all?


  • 2
    Not sure how long it should take, but after 24 hrs one would suspect that there's been some hickup along the way. I would recommend trying the ArcHydro tools' Flow direction function instead. It is a free (ESRI created) extension for flow path analysis and more.
    – Martin
    Nov 19, 2013 at 15:39
  • I don't see why it wouldn't work with negative elevation values, but what do you mean when you say that the DEM was inverted?
    – thwllms
    Nov 22, 2013 at 18:01
  • I mean I took the DEM and multiplied it all by -1, to get a flow path from 0 'uphill' (long story). Then I ran the accumulation on that. One thing I wondered about is where the flow accumulation algorithm chooses to start? Does it need a single highest point?
    – AnserGIS
    Dec 3, 2013 at 15:08

2 Answers 2


I'm guessing you mean CPU activity, and not GPU? ArcGIS doesn't use the GPU for number-crunching, unfortunately. If your machine has more than 4GB of RAM, make sure you have the 64-bit Geoprocessing addon installed. Without it, ArcGIS will be limited to using 4GB of RAM for a geoprocessing task. Also, ArcGIS can't use more than one CPU core on a geoprocessing task, so you want to make sure you're getting the most speed you can out of each core. You can do a few things to help:

  • Make sure hyperthreading is turned off. You can check this by going to Task Manager > Performance. On a quad-core CPU, you should see 4 CPU activity boxes: enter image description here

    If you see 8 boxes, hyperthreading is turned on and you'll need to go into your PC's BIOS and turn it off.

  • Make sure turbo boost is turned on if your CPU supports it.

As far as determining whether or not ArcGIS is still working or has quit on you, as far as I know there's no guaranteed way to know, but watching the CPU and memory usage of the ArcGIS process usually helps me. If CPU usage and memory usage both stay the same and don't change over time, that's usually not a good sign. If one or both fluctuate up and down, that usually means it's still working.

  • Looks like it is not working then. I will try a new smaller DEM with your process optimisation tips. Thanks!
    – AnserGIS
    Nov 20, 2013 at 8:17

I am also running flow accumulation, and the same thing happens to me- runs for hours and hours with no signs of life. My latest run went for 28 hours before finally giving an error. When I did flow direction, it regularly took at least several hours. Based on what I've read elsewhere and my experience, I think this is normal, though perhaps can be improved with system adjustments. Just be patient!

  • Last attempt, on a fraction of the data set crashed after several days. I suspect the problem may be a circular flow path which ESRI notes as a potential issue leading to an infinite processing loop. I did use the ArcGIS DEM sink filler and flow direction tools, but I think I have spotted one on manual inspection.
    – AnserGIS
    Dec 3, 2013 at 15:03

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