 His cycle of erosion suggests that (larger) rivers have three main stages of development, generally divided into youthful, mature and old-age stages.Each stage has distinct landforms and other properties associated with them, which can occur along the length of a river's upper, middle, and lower course.Though the cycle of erosion was a crucial early contribution to the development of geomorphology, many of Davis' theories regarding landscape evolution, sometimes termed 'Davisian geomorphology', were heavily criticized by later geomorphologists.