Absolutely. That's what
Geoff Lawton seems to have been doing when using gabions in Jordan. Slowed
water dropped a lot of clay, a little sand, a little organic matter and some other stuff, and over time that built up to a soil bank.
I don't know of any studies that specifically look at the composition of 'dropped' soils like this, I would hazard a guess that their makeup would vary widely. If you are only gathering a little, it shouldn't hurt to throw it in the mix. If you're harvesting a lot (like
enough to be its own field), probably have it tested just like any other soils to check for possible contaminants and what if anything needs amended.
I've thought about this a lot myself- here in Texas repeated vast floods have picked and tossed around whole feet of soil in some places in just the last few years.