Konwergencja form ukształtowania terenu w różnych systemach morfogenetycznych

Similar land shapes may be formed in different morphogenetic systems. The morphodynamic activity of proglacial rivers resembles the activity of intermittent streams in semi-arid and arid climate. In the foreland of glaciers and in arid areas there is no dense vegetation and periodically swelling rivers are heavily loaded with transported material. That is why they cannot cut into the substratum but rather tend to side erosion, channel migration and periodical surface wash. This favours fast levelling of the ground. In arid climate intermittent waters, first of all, shape the pediments which expand owirng to parallel withdrawal of slopes. Below the levelling zone there is the accumulation area, comprising the valley as well as the parapediments. As regards the origin and outer geatures pediments mostly resemble erosive plains of thawing waters formed at the outlet of sub- and inglacial tunnels. They are frequently shaped by the surface wash of waters which flow out of their channels and over the whole surface slightly sloping in the distal direction. Valley bottoms and parapediments filled with deposits resemble outwash plains which develop on former depressions.