Hi Camila,
I’m having the same problem with my HEC-RAS (4.1) sediment model (using SI units also)! I was modeling a complex reservoir when I started noticing that the sedimentation was unrealistic.
Then, I created a simple flume model to try to understand what was going on. My boundary condition is a constant sediment influx of 3.456 tons/day. However, HEC-RAS says that the sediment flux into my first cross section is 4.20 tons/day (1.2 times higher).
I still haven’t figure it out if I’m doing something wrong or if this HEC-RAS version (4.1) has a problem in the sediment model.
If I discover something, I’ll let you know. In the mean time, let’s hope that someone can give us an answer.
Sincerely,
Mario Grüne