Won't Run After Adding Junction

[Hydro Modeler]

Hi All:

I am trying to run an unsteady flow model and I am having trouble getting it to run after I add a tributary and junction. The model is fairly complex, it is about 20 miles long, has 2 storage areas, 2 dams and about a dozen bridges. Without the junction and tributary it runs well, however after I add them it won't even begin to run: it fails right away. The failure errors are generally in the reach below the junction. I am wondering if anyone has any suggestions for getting it running.

Here is what I have tried so far:

1. Adjusting the distance across the junction by small amounts
2. Adding a pilot channel to the tributary so that the tributary invert is at the same elevation as the main channel
3. Adjusted the base flow in both the main channel and the tributary
4. Changed the computation time step through a wide range of values
5. Tried both the energy and momentum solutions
6. I also tried flooding out the system (and slowly returning to the normal flow conditions) to generate a restart file

None of this seems to have any real impact on getting it going. Anyone have any suggestions?

Thanks in advance.