which earth materials are deposited first as the water in a river slows down?

Answer 1

All the heaviest materials would be deposited first. When the force of the water falls, then the mass and weight of whatever material is being forced along with it will come into play. The heaviest of the dense material (like boulders) will be deposited first. Then whole trees (which because of their size tend to float better, but eventually the weight of them will be more than the force exerted on them). Then smaller rocks, etc, etc, etc, until you get down to light silt which would be the last particles to fall to the stream bottom.

Answer 2

the heaviest stuff will be deposited first, normally it would be sand and silt(the heavier ones)
of course that's the reason you would pan for gold .
as you swirl the water and the rest of the stuff in the pan only the heavier stuff is left behind and that makes it easier to find the gold.
God bless,
gabe

Answer 3

ground rock as sand or silt ( it is a simple thing the dense materials first - the denser the sooner )

Answer 4

The most dense or heaviest, like rocks.