ArcSWAT 2.0.0 crashes: user-defined watersheds

[dwhydro]

I keep getting crashes of the ArcSWAT interface and I am not sure
where to turn. I am running ArcSWAT 2.0.0 for ArcGIS 9.2 and I have
scoured the listserve for clues as to how to repair. I appreciate all
of the solutions that do get posted but several of us seem to not have
good solutions for user-defined watersheds in ArcSWAT 2.0.0.

I need to use predefined watersheds and streams for my prescribed TMDL
project. During the watershed delineation phase, I make it through all
of the steps until the end. After "calculating subbasin parameters"
completes successfully, the process begins writing output files as
"exporting grid databases". It is at this point that I get an
"unhandled exception" error from Microsoft NET
(RasterDataset::get_Count). I continue through the error and the
process is hung.

When I bail <ctrl-alt-del> and re-enter my SWAT project, I continue to
receive a suite of subsequent errors. I have to start over because
none of the previous steps are defined. This can become quite
cumbersome because I must manually define my 25 point sources.

To note, the fields of my user-defined watersheds and streams files
all follow the naming conventions prescribed in the documentation.

One possible culprit is my DEM - the cell size is 10 ft (!) and grid
file size is 32 GB - I have 150,000 rows and 125,000 cols. The DEM is
unsigned int. Both value and count fields are integer. If I am only
using the DEM for slope calculations, perhaps I should coarsen the
resolution to say a 30 m grid and reduce the grid size?

Thanks for reading!
Dale

[Michael Winchell]

Dale,

Given your large DEM and the error you describe, it sounds like you
may be blowing over the 2 GB limit of the Access RasterStore.mdb
geodatabase. If your RasterStore.mdb geodatabase is at or near 2 GB,
then this is likely the problem. ArcSWAT keeps its rasters in
temporary GRID format datasets during the delineation, then exports
them into a geodatabase when delineation is completed.

Your idea of using a lower resolution DEM is definitely worth trying.

Mike

[dwhydro]

Michael - thanks for your response. You are correct. I coarsened my
DEM by a factor of 10 (using the Arc AGGREGATE command and I have been
able to move through the delineation phase. Thanks again!