The given statement is False.
As the water velocity decreases, the size of the particles that the water can transport also decreases. For example, as the velocity of the stream increases, the stream can carry larger sediments. It is noted that the physically weathered sediments are bigger in particle size in comparison to the chemically weathered particles.
In case, if the velocity of water is too slow and the slope is too gentle, then the rate of transportation of sediments also decreases and the sediments get to pile up.