Downstream, the Colorado runs clear and erodes into its channel. During Pleistocene glaciation, many rivers draining meltwater away from the ice sheet carried huge sediment loads, which resulted in aggradation in floodplains. After the ice melted, the dramatic loss of sediment load initiated downcutting into the floodplain deposits. This produces terraces . In arid regions of the southwest, it was much wetter in glacial times.
Streams erode channels, produce arroyos, or dry gullies.
This would steepen the longitudinal profile and stream gradient, allowing faster runoff and higher discharge. During glacial times, when ice mass was large and oceans reduced in size, base level dropped as more continental shelf was exposed. With time, this degradation would be progressively transmitted upstream. E. Overall - 1. Streams spend long periods in equilibrium, without dramatic aggradation or degradation.