Lithospheric plate movement
Rivers and the valleys that they occupy were affected strongly by the changing climates of the Pleistocene. River channels and their sediment record are controlled in large part by the amount and type of load that is supplied by their drainage basins and the discharge or quantity of water available for flow.
Both are closely related to climate, which not only includes precipitation, evaporation, and seasonality but also controls the extent of the vegetative cover of the land and the type and intensity of weathering processes.
In addition, because of sea-level changes related to glaciation, the base level of rivers in coastal regions also fluctuated by significant amounts. As a result, river environments were dynamic and variable.