Error in HEC RAS 3.1.2 or 3.1.3 ?

[mjvclv]

All

I've come across an issue when running a simple steady state HEC RAS model on the current and previous version of the software.

The models produce similar results except at a certain bridge - when ver 3.1.3 produces upstream WLs some 100mm higher than the former version. Give that the previous model was used to justify a flood defence scheme, the new results mean both a need for a higher defence and possibly more do-nothing justification.

I can find no explanation for this change in the updates.

Examination of the log files show that the models are considering the slicing of the section at the bridge in different ways - with the old model possibly incorrectly acquiring the cross sectional width and hence has different slices for its computations. The log files are attached - everything in the runs are identical apart from the software version they’ve been run on. Row 1270 where the files diverge

Ver 3.1.3 =
PROPERTY SLICES -- NUMBER, STARTING STATION, ENDING STATION
1 -16.7 -3.3 2 -2.9 0.0 3 0.0 36.4 4 36.4 37.4 5 38.0 89.8



Ver 3.1.2 =
PROPERTY SLICES -- NUMBER, STARTING STATION, ENDING STATION
1 -61.7 -35.9 2 -35.9 0.0 3 0.0 36.4 4 36.4 140.2


Is the software mixing up the -16.7 and thinking its -61.7 in version 3.1.2 (-16.7 is close to a point in the cross section and the overall sluice width of -16.7 to 38 is inside the overall XS width - whereas the data from 3.1.2 don’t seem to correlate with anything).

Any ideas or comments welcome.

Thanks

Mike