Importing an old HEC-1 file to HEC-HMS (error messages)

The ST record defines dam overtopping flow using the weir equation. The EXPL parameter is the exponent on the H (typically 1.5). I don't think HMS has the capability to change the exponent so it is not surprising it is ignoring this value.

You should be able to open the .IH1 in a text editor and see what the ST record contains. Compare what is in the .IH1 to what options are specified in the HMS model for RT#5. Also look for the SV (or SA), SQ and SE records that specify the volume (or area), discharge and elevation tables and compare to the HMS paired data.

The ST record has 5 columns: ST, Elevation, Crest Length, Coefficient(Cd), exponent (1.5).

I think there may be inconsistencies between the paired data the program has and what is required (storage-discharge vs. elevation-discharge), perhaps because the program is trying to mix specified rating curves with specified spillways.

Make sure the appropriate method options are chosen for the paired data or spillway data you have. And, make sure the appropriate paired data tables are selected in the basin model element.

If it is truly just a slight revision, I'd think it would be easier to make the changes you need to the .IH1 file and keep it in HEC-1.

You can find the HEC-1 program and documentation that describes each record in the .IH1 file at:

I tooled around with HEC-1, but decided to go with HMS because I wanted a visual representation of what was going on in the model, as it's a brand new model to me. Never seen it before. I didn't even know which pond I needed to modify before importing it to HMS, honestly, it's a ten year old project I've never seen.

Now that I've found my way around, it might be easier to use HEC-1 instead.

Thanks for the info on which columns mean what / etc. That's exactly the sort of input I was looking for.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

Surprising though that the HEC 1 file doesn't work in HMS.

Maybe it lack of data in the original file: ERROR 41587: Elevation-discharge table "" for reservoir "RT#5" must contain at least two rows.

and has some error in it:
Independent variable, 1032.03, is above maximum table value, 1032.0

1032.03 > 1032.0 heh.

Well yeah, that was the easy one to find, SMIAH.

I'm back to just running the thing in HEC-1.



Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

You Have My Deepest Sympathy...

Hopefully you have the required 2.5 Mb total memory to run that thing.

I think I'm going to expense a new laptop just to handle the run times.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -