Errors in stage and flow hydrographs

[Miriam]

I am trying to perform an unsteady flow analysis using HEC-RAS 3.1.

Though the simulation aledgedly completed successfully, I have discovered that the stage and flow hydrographs have done something strange. For each cross-section the first stage/flow has been calculated correctly but thereafter the values for stage and flow are the same negative values regardless of the time step or cross-section.

For example, the most downstream cross-section (which is also the downstream boundary condition of the model) should reflect the tidal cycle that I inputed into the model, but instead it has a stage and flow of 0.57 m and 29.01 m3/s respectively for the first time step, and then -274.62 m and -25.51 for the remaining 86 time steps.

The first time step of the cross-sections which act as upstream boundary conditions to the model is correct, but the remaining time steps also have the values -274.62 m and -25.51!

Any help would be greatly appreciated!

Thanks

Miriam