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.
Usually, these are brief periods of aggradation or degradation, until a new equilibrium of efficient sediment transport is established.