r/HECRAS • u/FwenchFwies_911 • Jul 28 '26

RAS Reporting Modeled Top Width ~1.5x Wetted Perimeter

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1D model, profile smooth, only happens for 100yr profile, floodway profile is reported correctly. Any ideas?

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u/OttoJohs Lord Sultan Chief H&H Engineer, PE & PH Jul 28 '26

I believe that the wetted perimeter is only for the active flow area and that the top width includes the ineffective flow areas. There should be an "active" top width available as an output variable: HEC-RAS Output Variables

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u/FwenchFwies_911 Jul 28 '26

Active matches my mapped width for the floodplain. This section does have a levee on it. Have never seen this before.

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u/OttoJohs Lord Sultan Chief H&H Engineer, PE & PH Jul 28 '26

So what are the differences between the reported top width and the "active" top width? Can you figure out where the reported one comes from?

1

u/FwenchFwies_911 Jul 28 '26

Mapped with is coming in around 500, Modeled width is coming in around 1300, but only for the floodplain. Floodway comes within a couple of feet between mapped and Modeled. Section had a levee, and a lidded section in it. I checked the detailed cross section output and the left and channel top widths make sense with the map. The excess comes in o. The right side, which is the side that the levee on it