underfit stream

An underfit stream is a stream that is significantly reduced in volume and, consequently, in its capacity to erode or transport material. This reduction is often a result of stream piracy, where one stream diverts the flow of another.1

The phenomenon of underfit streams is frequently linked to climatic changes. Over time, shifts in climate can cause a stream's channel to shrink considerably from its former dimensions. This means the existing channel is much smaller than the valley it flows through, which was carved by a larger, more voluminous ancient stream. The reduction in channel size is often accompanied by the infilling of former larger channels, with existing floodplains contained within these fills. While climatic change is a primary driver, other factors like sediment transport variations and the role of rare, large floods can also influence stream underfitness.23