Final answer:
Rivers progress through three stages of development: young, with narrow channels and fast flow; mature, which are wider and have moderated flow; and old, characterized by slow, meandering water with extensive floodplains and features like oxbow lakes.
Step-by-step explanation:
Rivers are categorized into three main types: young, mature, and old. These categories reflect the stages of a river's lifetime. Young rivers are characterized by their narrow, often deep channels and fast-flowing, clear water. They usually have steep gradients, leading to swift currents and the capability to erode their beds, carrying sediments and larger materials downstream. Mature rivers have wider channels with less gradient compared to young rivers, and the water flow becomes more regulated. Erosion remains a significant feature, but it is more lateral than vertical, which widens the river valley. Lastly, old rivers are characterized by very broad, slow-moving waters. The low gradient leads to meandering courses, and extensive floodplains with features like oxbow lakes and levees become prominent. In this stage, sediment accumulation often exceeds erosion.