Floodplain-Channel Flow Exchange - Text Reporting Clarification

Hi, I'm modeling a depressed roadway about 1250 ft long and at about 15 feet deep at the lowest point compared to the surrounding floodplain elevation. The roadway is cutting through a railroad embankment modeled as levee 6 ft tall compared to the floodplain elevation. The depressed roadway starts at the floodplain elevation about 600 ft upstream of the railroad and keeps getting deeper until right below the railroad crossing and then starts rising in depth until getting back to the floodplain elevation in about 600 ft downstream of railroad crossing.

I'm modeling the depressed roadway as rectangular channel and its width is 2 ft less than the octagonal side of the cell. The flow between two sides of the railroad embankment is only through the channel and the 2 ft floodplain.

As expected, on both the upstream side and downstream side, there is a lot of floodplain-channel flow exchange. I also have put two one- element floodplain cross-sections: one on the upstream channel cell and the other on the downstream channel cell.

My questions are
(1) is the modeling approach valid? My results suggest that the hydraulic behavior is reasonable.
(2) flow depths reported in Base.out, Hycross.out, hychan.out and other out files, do they report the depths before the floodplain-channel exchange or after the exchange? The results I have suggest that the reported depths are before the exchange, if so, is there a way to obtain the depths after the floodplain-channel exchange?

Thank you

I don’t see anything wrong with this approach. I would review the velocities in VELTIMEC.OUT and VELTIMEFP.OUT to make sure there is no surging in the model. Make sure the velocities area reasonable. If the flow is very slow, you may need higher n-values to avoid surging. If you model a small discharge, so that there is almost no flow, check the water surface elevations for reasonableness.

The depths are always reported after the floodplain channel exchange. The sequence is:

Channel routing
Floodplain routing
Update results
Channel floodplain exchange
Update results
Write to output files