Problems with Flow accumulation tool

[CarlosCanas]

I'm still having problems with Flow Accumulation tool in Hydrology/Spatial Analyst.
Arcmap shows work in progress (It says: "Updating flow accumulation..."), however it never ends. I've tried with Arcmap 9.3, Arcmap 10.
I just created a new raster of flow direction, in the case the previous I used was corrupted, but the problem still: the process never ends and I have to stop it (last time it was done was during a whole weekend). I've donde same process for other regions and it worked very well, this situation just started to occur a couple of weeks ago.
I'm very concern whether something is wrong with my data (license and extensions are checked, and ok) or it is something happening with the tool and there is a solution (patch, or similar from ESRI).

please, all help will be very appreciated.

[ChrisSnyder]

How big is your input flowdir grid (pixel height x pixel width)?

Flow accumulaton can take an extreemly long time to run on large grids. I have had some flow accumulation process take a week to run on a fast machine.

A few days of run time probably isn't that bad!

The larger the flow accumulation you have in your data, the longer the tool will take to run. So, for example, it will take much longer to run for a grid mostly composed of a large single basin that drains to one point (like the Amazone River) than a grid of the same size that has many smaller basins that drain radially outwards from the center (like Mt. Kilimanjaro).

[CarlosCanas]

Hello Chris,
thank you very much for your response.

How big is your input flowdir grid (pixel height x pixel width)?
If I'm not wrong (I calculated height and width after extent information of my raster, already projected) this raster has 8779 pixel-height by 7904 pixel-width (I subtracted top - bottom, and right - left in extent information, and then divided both by pixel size...was that correct?).

Flow accumulaton can take an extreemly long time to run on large grids. I have had some flow accumulation process take a week to run on a fast machine.

After I read your response on Friday I left in 2 machines the tool running, came back after the weekend and both are still working, one lost connection to the server (now is back connected, and continue with the process) and the other says "updating flow accumulation" and arc map is not appearing/displaying the raster, only the status bar shows work in progress ("Updating Flow Accumulation"). I will leave for some more time, as you suggested.
However, I've done same tool/process with same raster source but for different regions and -I would say- such similar large area size, and it worked very well, I have delineated my drainage areas/polygons for other 2 nearby regions. Yes, it took time (a few hours) for those previous, this situation appeared for this last region.

The larger the flow accumulation you have in your data, the longer the tool will take to run. So, for example, it will take much longer to run for a grid mostly composed of a large single basin that drains to one point (like the Amazone River) than a grid of the same size that has many smaller basins that drain radially outwards from the center (like Mt. Kilimanjaro).

this is also true in my case, this area has several large sub-basins (Amazon System) that drains off the country limits, that is: several tributaries with other tributaries that has no ONLY ONE outlet in common. That is perhaps the reason, and the difference when compared with my others areas, that this raster process may take longer time. I'll leave the process for more days.

Once again, thanks for your help!

[ChrisSnyder]

one lost connection to the server (now is back connected, and continue with the process)

You might be referring a license server here, but...

One of the largest performance enhancements you can make with any ArcGIS tool is to processes the data using your local hard drive(s). That is, don't try to run these processes from data stored on a network.

Also, I assume you ran the Fill tool on your input DEM (before you made your flow directions grid), correct?

[CarlosCanas]

You might be referring a license server here, but...
not problem with license, I've checked that too.

One of the largest performance enhancements you can make with any ArcGIS tool is to processes the data using your local hard drive(s). That is, don't try to run these processes from data stored on a network.
In both cases, rasters are placed on main drive (C:/).
What it's interesting is that in both cases the Flow Accumulation status is shown as "in progress", and on the background the open ArcMap says: Not responding.
Since the message in the status bar is: UPDATING FLOW ACCUMULATION, that means ArcMap is in processing and that is why "IS NOT RESPONDING"?
This time I've not even try to touch this process and it still on...since last Friday.

Also, I assume you ran the Fill tool on your input DEM (before you made your flow directions grid), correct?

yes, DEM was projected, filled, etc.

As said before: since I've done same thing for the other regions all of a sudden this problem just started, I felt it was a like-bug in the tool, or something. Is that possible?
I was thinking to run one of the rasters I did before, to check whether the problem occurs or not (since those raster were processed with no problems in a few hours of processing, if they do not work now it's because is a tool problem).

[SpatiallySpeaking]

I'd be interested if you find any errors in the tool or know of a way to run an analysis on subsets and then combine the results (unlikely possibility, I know).

I am running into the same issue.  I successfully ran Flow Accumulation on a 90m grid (filled, all best practices, etc.) for a very small area (less than 1 MB).  The process ran in around three minutes.  I am now trying to compute flow accumulation for the same area using a 20m grid (still very small file size, I believe less than 2 MB).  I let it run overnight and absolutely no change (I wish ESRI would include a standard progress bar to let you know if the process was actually making progress).

It seems like moving from 90m to 20m shouldn't increase processing time this exponentially.

[curtvprice]

It seems like moving from 90m to 20m shouldn't increase processing time this exponentially.

It will because the number of cells increases by the square of the cell size. So if you ere processing 10,000 cells going from 90 to 20m increases the number of cells to process by a factor of more than 20!

[RalphElsaesser]

For a grid of 24.ooo x 18.ooo cells the flow accumulation calculation took me 4 hours with a 64-bit Windows 7, ArcView 10.1, 8GB RAM and a 2.60GHz Dual Core processor.