An Important Question

1) Norrish Creek
2) Illecillewaet River
3) South fork of Thor Creek



How often do some of the visible clasts in these streams move? Yearly? Once a decade?
If they are largely immobile, and hard to measure using the photogrammetric method, then is the channel-forming discharge the discharge at which they move and not the effective discharge that moves finer sediment through without moving these large clasts?