Youthful river

At the start of the 20th century William Morris Davis devised the “cycle of erosion” method of classifying rivers based on their “age”. Although Davis’s system is still found in many books today, after the 1950s and 1960s it became increasingly criticized and rejected by geomorphologists. His scheme did not produce testable hypotheses and was therefore deemed non-scientific.[8] Examples of Davis’s river “ages” include:

Youthful river: A river with a steep gradient that has very few tributaries and flows quickly. Its channels erode deeper rather than wider. Examples are the Brazos, Trinity and Ebro rivers.
Mature river: A river with a gradient that is less steep than those of youthful rivers and flows more slowly. A mature river is fed by many tribu

taries and has more discharge than a youthful river. Its channels erode wider rather than deeper. Examples are the Mississippi, Saint Lawrence, Danube, Ohio, Thames and Paraná rivers.
Old river: A river with a low gradient and low erosive energy. Old rivers are characterized by flood plains. Examples are the Yellow, lower Ganges, Tigris, Euphrates, Indus and lower Nile rivers.
Rejuvenated river: A river with a gradient that is raised by tectonic uplift. Examples are the Rio Grande and Colorado River.
The ways in which a river’s characteristics vary between its upper and lower course are summarized by the Bradshaw model. Power-law relationships between channel slope, depth, and width are given as a function of discharge by “river regime”.