HEC-RAS Version Difference

[jeffd64]

Hello,

I acquired HEC-RAS input from FEMA. The version that was used to calculate the floodways and natural flow values was HEC-RAS V. 2.2. We are currently using HEC-RAS V4.1. When we run the FEMA input our water surface elevations for the the floodways are off by at least 0.5 ft or more. Are there computational differences between 2.2 and 4.1 when using encroachments. Also does anyone know where to get the all the release notes for the HEC-RAS programs?

Thank you

 

[beej67]

I've seen variations, but 0.5 seems like a lot. Makes me wonder if there isn't a data entry error in the file that's being interpreted differently by the two versions. I've seen that sort of thing crop up converting HEC-1 to HEC-HMS.

If you're submitting to FEMA for something like a CLOMR, you should by rights be able to run the old 2.2 model in 4.1, and then use the 4.1 elevations as your "corrected effective" elevations to match against.

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

http://www.campbellcivil.com

 

[SMIAH]

Download the 2.2 version and run the file?

http://www.hec.usace.army.mil/software/hec-ras/downloads/ras22_cd.exe

 

[jeffd64]

I downloaded HEC-RAS 2.2 and kept getting an error saying memory is too big....... I do not know why I get this error.

 

[beej67]

Try running 2.2 in a windows virtual machine interface. Google it. Not sure it matters, but it might, because 2.2 came out before 64 bit processors.

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

http://www.campbellcivil.com