Differences between HEC-RAS 3.0 & 3.1 calcs

Chris,

I would like to ask you if you have noticed differences in the calculations between HEC-RAS 3.0 and the new version 3.1. We have observed differences in WS elevations, EG elevations, flow areas, etc. in areas of standard step calculations (with no bridges and no supercritical transitions). We have noticed changes around bridges, but the release notes describe new methods for calculating weir flow and such around bridges. I would like to know if you have noticed these changes, if you know what changes have been made to the program to cause these changes, or if you have any explanation. We are using the same geometry, same flows, and the only difference is the version of the model.

Any help would be appreciated.

William Thomas
Hydrologist
Walter Schoel Engineering Co.
Birmingham, AL

[Chris Maeder]

Bill :

I have had quite a few people complain that the WSEL computed in HEC-RAS 3.0 is higher than in HEC-RAS 2.2, and HEC-RAS 3.1 is even higher than in HEC-RAS 3.0. From what I have seen, it is the upstream bridge and culvert cross sections.

I have not been able to pin down a reason for the higher WSEL. Supposedly the hydraulics have been improved. However, it is discouraging to have a valid design in 2.2, and then have if not work in the newer versions of HEC-RAS because the WSEL is now higher.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com