From this observation geologists calculated a relationship between the velocity of moving water in a stream or river and the size of particles that water can transport. If the river velocity exceeds the settling velocity, the grains will remain suspended. Delta form where river water slows down when it hits a large body of water such as a lake or ocean. When a delta gets very large like the Mississippi Delta, river sediments are actually carried through the delta and to the delta front before being deposited. Distributary channels form because the top surface of a delta is particularly flat and spread over a broad, flat region.
Water can easily spread laterally over a flat surface much as it does on a table top.
In class on Tuesday you mentioned that larger particles such as rocks bounce down rivers while the smaller particles remain in the upper portion of the river. Yes, when pebbles bounce by saltation, they can chip and break. Eventually the particles of X-pebble can become small enough by mechanical weathering that they become sand, silt, or even clay. I must not, however, that even clay is so dense that it will not float. Clay stays in suspension because the river current carries it and will not let it sink.