Hi @frank -
If you search this forum, you’ll find that this is a recurring topic, and I’m not sure that it has a definitive answer yet, but I think we’re closing in on using sed_deposition to represent sediment retention (which means that we should probably remove or at least rename the sed_retention outputs). The sed_retention outputs should not be interpreted quantitatively, but sed_deposition can be.
Here’s one of those threads, which I suggest reading through. In it, the software developer of this model says this: “I suspect you actually want the downslope sediment deposition raster. It gives a good estimate of where sediment that has run off from a pixel has been retained downstream by the vegetation on the landscape: SDR Sediment Deposition User’s Guide Section .”