Arc Hydro Characterize DEM - Flat Area Raster step fails

[Eric_Chameroy]

Hello everyone,

I'm stuck on the Characterize DEM tool in the Arc Hydro Erosion Toolset. Every time I have attempted to run the tool, it produces a landform raster but then fails on the next step: identifying flat areas and generating a flat area raster.

I found a recent post that seems to be addressing the same issue:

Arc Hydro Pro Identify Flat Areas Error

However, there doesn't appear to be a clear solution. Has anyone else come across this issue? Is there workaround?

Thanks!

[DeanDjokic]

i've tested the function on few of the DEMs (with/without initial flat areas and with/without projection) and was not able to reproduce the behavior you are describing.  please make sure you are using the latest version of Arc Hydro tools for your version of Pro and retest.  if that does not work we need to test on your dataset.  please provide:

1. version of Pro you are using.

2. version of AH tools you are using.

3. zip the DEM (seems large enough that you will have to share it through a file share) and send the link to archydro@esri.com.

Dean

[Eric_Chameroy]

Hello Dean,

Thank you for looking into this for me. I've sent a OneDrive link to a ZIP archive containing the DEM. It's a very large file (> 3 GB) with a resolution of approximately 2 cm. It covers a very small area and was generated from drone imagery.

I'm using the most recent versions of both ArcGIS Pro (3.4.3) and Arc Hydro (1.0?; archive name contained 3.4.9).

I don't know if the resolution of the DEM is the issue. So far, I have not run into any issues when using it to create a stream network using either Arc Hydro or the Hydrology tools.

Best,

Eric

[DeanDjokic]

thanks for sharing the data.  we were able to reproduce the error using your dataset.  trying to figure out what the issue is - the code fails on a standard arcpy.management function that works fine on other data.  could be the size of the raster or something else, so we'll have to dig a bit deeper.  there is a manual process you could follow but it is a bit tedious (that's why we built the tool), so if this is critical, you can do it that way - i can send you the steps.  otherwise we'll try to have a fix early next week.  

[DeanDjokic]

We have implemented a workaround for the problem that you have reported.  For Pro 3.4 you can use AH version 3.4.20.  Direct download is on:

https://downloads.esri.com/archydro/archydro/Setup/Pro/3.4/3.4.20/

Note that this is not a "signed" version of the tools (thus direct download instead of going through the regular download process).

As always, first uninstall the old version of AH before installing the new one.

Another thing to note - with your tiny cell resolution and extent, the default tool parameters will not generate any flat areas - you need to reduce the minimum size to something small before you will get anything in return.  If you keep larger minimum area, the tool will return the warning that no area match the criteria and the output layers (besides geomorphon raster) will not be generated.

Please test and let me know how it goes.

[Eric_Chameroy]

Hello Dean,

Sorry for taking so long to get back to you. I wanted to try some things before responding.

One thing I noticed is that the DEM I sent you did not have a vertical coordinate system, which I have since added; I'm not sure if that could have been a factor. The other thing I had done, since you mentioned that the high resolution of my DEM could be an issue, is to use the Identify Flat Areas tool instead of Characterize DEM so I can adjust the minimum flat area threshold.

I seem to be getting the desired results now.

Thank you again for the help.