HEC-RAS permanent ineffective flow areas

[aliferr]

I have a project where I am modeling an existing culvert and a replacement culvert in HEC-RAS. I know I need 4 cross section for culvert modeling – 2 upstream and 2 downstream (Fig 6-3 in Chapter 6 HEC-RAS Ref Manual). Regarding the ineffective flow areas at cross sections 2 and 3 – I know which elevation to set them at, but the question becomes – do I set them as “permanent” or “non-permanent”? I did find some description in the HEC-RAS Hydraulic Ref Manual for ineffective flow areas at bridges which implies "non-permanent" but does not explicedly say it. It is my understanding these areas will be blocked regardless whether the water will be going over the roadway or not, these areas will not be flowing since they will be obstructed by the abutments and the water will only flow in these cross sections through the culvert itself and over the roadway weir if the flow gets high enough. Am I correct?

If I am incorrect, can anyone give me an example on use of "permanent" ineffective flow areas?

Thanks!