What geomorphic features are indicative of a mature river?

A mature river is typically characterised by features such as meanders, floodplains, and oxbow lakes.

A mature river, also known as a 'stage two' river, has distinct characteristics that set it apart from youthful or old age rivers. One of the most noticeable features of a mature river is the presence of meanders. These are large, looping bends in the river that form as the water erodes the outer banks and deposits sediment on the inner banks. This process, known as lateral erosion, is a key characteristic of a mature river and results in a wide, flat valley floor.

Another significant feature of a mature river is the development of a floodplain. This is a flat area of land on either side of the river that is prone to flooding. It is formed as the river erodes its banks and deposits sediment during periods of high flow. Over time, this process creates a wide, flat area that is often rich in nutrients and ideal for agriculture.

Oxbow lakes are another common feature of mature rivers. These are formed when a meander becomes so pronounced that the river cuts through the narrow neck of land between the bends, creating a new, straighter channel. The old meander is left behind as a crescent-shaped lake, known as an oxbow lake.

In addition to these features, mature rivers often have well-developed tributary systems. These smaller rivers and streams feed into the main river, increasing its volume and contributing to its erosive power. The presence of a complex tributary system is another indication of a river's maturity.

Finally, mature rivers are often characterised by a balanced load of sediment and water. This means that the river is capable of carrying the sediment it erodes without becoming choked or blocked. This balance is a sign of a river's maturity and is crucial for the continued development of features such as meanders and floodplains.