Unsteady Flow HEC-RAS Model Troubleshooting

Chapter 3 Cross Section Issues

Cross Section Issues

1. Place additional cross-sections at locations where the model cannot converge on several time

steps. Keep in mind that if the cross sections are placed too close together, the numerical

solution will cause wave steepening and the model will go unstable on the rising limb of the

2.

following situations:

versa.

versa.

3. It is better to use real terrain geometry for constructing additional cross sections rather than

just interpolating cross sections.

4.

structure should also overtop and not be blocked.

5.

Ineffective flow areas should be marked as “permanent” so that during the routing, the

large increase in conveyance area and cause the model solution to oscillate by having an

the next iteration or time step.

6.

conditions.

7.

cross-section invert.

8. Revise the hydraulic parameters for every cross-section and structure to provide additional

conveyance curves can be minimized by adding additional horizontal Manning’s roughness

locations.