Inconsistent flow depth over flat area (2D)
There's something I'm trying to make sense of, and I figured its worth seeing if anyone here could shed some light on it. I have a completely flat area (about 10ft across) that is getting only partially inundated. As you can see from the plots along this profile line, the elevation is the same all the way across, however there is over 2 inches of depth on one side.
I'm fairly new to modeling in general. I know that models are never a perfect representation of reality, but how is this physically possible?
Here is the water surface elevation (at its local peak) and terrain along this line extended further upstream and downstream:
As you can see, there is a flat WSE over the deep spot upstream of my area in question. This WSE extends over the flat berm, and then drops off pretty quickly at a certain point and there is no flow depth. It then picks up again downstream at a similar slope, as if it just clips through the terrain.
I would expect this whole berm to be submerged under a consistent WSE, and then for the WSE to drop off with the slope of the terrain after the terrain starts sloping down rather than before.
What kinds of things might cause this? Is this normal for HECRAS?
The time series of WSE at this area shows its peak at exactly 13:00:00, the time of the profile above, but could it be that this result is showing a moment that is some infinitesimally small amount of time before the actual peak, and when the WSE is still rising? Is this just a snapshot of the flood wave in motion? The time step is 0.1 second. I'm not sure how to view a profile for the absolute max in a specific area, as the "max" feature seems to just show the moment in time where the maximum value occurs anywhere in the model, so I just looked at the time series and physically dragged the slider to the time stamp where it shows the peak. The upstream side of this berm remains submerged under some amount of depth for a period of about 1 hour, while the downstream side is never submerged at all, so I guess there is always going to be a weird drop off somewhere no matter what time it is viewed.
Edit: I just realized that the drop off occurs exactly at the boundary between one cell and other. My mesh is very refined, so that there's three separate cells across this flat area.