No Critical Depth

[jsivils]

I am doing a hec-ras model. Everything is entered, as far as I can tell. I get a water surface elevation. I do not get a critical water surface. The 2 year event shows a critical water surface for about half the channel then it disappears. For the other profiles, not showing up. The 2 year critical intersects with the 2 year water surface where it disappears. I have changed the variables, to not show the water surface, but still it goes away at that spot.
Also on the tables I do not get a Crit W.S. for 2 of my cross sections at all. Then I get a critical W.S. that is equal to the W.S. on some of the cross sections. Never had this problem before. I am going to go through each of the steps again and make sure that I am not missing something.
I do get this warning in the warning report.
"Warning: During the standard step iterations, when the assumed water surface was set equal to critical depth the calculated water surface came back below below critical depth. This indicates that there is not a valid subcritical answer. The program defaulted to critical depth."

Any Tips on how to fix this? I know that the stream does not enter super crit flow at this area, at least that anybody has seen.

Thanks for the help.
Jason

[jfs175]

The quick fix in case you weren't aware...

Perform a steady flow calculation, go Options, Critical Depth Output Option, and "Critical always calculated".

If you are aware of this and this isn't the problem, then more x-sections are probably warranted either by cutting them or interpolation, or your roughness is too low.

[AbNormal_Depth]

Critical Depth is only calculated by RAS (by default) at "problem" locations. If Dc is not calculated, that indicates the answer at that section has a low Froude number and is subcritical. Critical depth is only calculated when the program thinks flow should go supercritical or can't find an "real" answer and defaults to critical depth.

If you have answers defaulting to critical depth, you need to fix your geometry: interpolate sections, create improved transitions from cross sections, etc.