Luther Aadland (video #1)
"Finer sediments are moved by lower amounts of energy, and larger sediments take more shear stress, or more energy, working on the streambed. And when those change, the ability of different parts of the stream have different abilities to move sediment. During a flood flow, in a meandering stream, the energy grade, or the dissipation of energy, is fairly uniform from riffle to pool. The velocities in the pool increase as flood flows increase, and with that is the increase in ability to move sediment. As flows slow down or become lower, the sediment starts to deposit. In riffles, large sediments can be deposited, things like gravels and boulders and cobbles. In the pools as flows come down, finer materials like silt and sand will deposit. And these again define the habitat that we have."