HEC-RAS - 1D Steady - Persistent Warnings

[ilopran]

I've built a HEC-RAS model for a stream I'm analyzing and can't seem to figure out why I'm getting persistent warnings for nearly all my cross sections. Initially I nearly doubled the amount of cross-sections, since most warnings said this typically indicates the need for more sections. At this point my river is approx. 2,750 LF and I have 72 cross-sections, seems excessive.

The warnings are:

1) During the standard step iterations, when the assumed water surface was set equal to critical depth, the calculated water surface came back below critical depth. This indicates that there is not a valid subcritical answer. The program defaulted to critical depth.

2) The conveyance ration is less than 0.7 or greater than 1.4. This may indicate the need for additional cross sections.

3) The velocity head has changed by more than 0.5 ft (0.15 m). This may indicate the need for additional cross sections.

I would assume this entire stream should be subcritical flow (stream slope is 1%-2%). The only supercritical section is through a culvert which I think makes sense.

I've attached the profile.

Any advice on how to troubleshoot this would be great. I've played with different boundary conditions, and searched through the internet and HEC-RAS resources and haven't found anything seemingly useful. Thanks.

 

[ilopran]

Attached is a new project I made of the same stream. Reduced the number of cross sections and greatly simplified the cross section geometry. Still running into the same issues.