U.S. scientists terrain Davis's first cycle of the concept of the creation of the river, when the river began to cut the original ground (has never been erosion and destruction of the ground), the river that is the beginning of the cycle. A cycle from start to finish the process to form the river of history. And at every stage of the process have different topographical features. Taii be divided into three stages, and early childhood, prime, and old age.
A childhood:
When the ground began to undermine the original, early childhood activities have started nurturing it. This phase of the topographical features of the cross section for the valley V-shaped surface, there is no flood plain along the river cross-strait development, the watershed between the two rivers is also a broad level, and rivers are often capture the phenomenon occurred. The hard rock in the river, which has occurred in falls or rapids. This phenomenon is particularly common in early childhood, to the former prime upcoming eradication. Childhood this stage is to make the original ground level to increase or expand the ups and downs and downs of the times, towards the end of childhood, the terrain is characterized by high mountains and deep valley, the ground is extremely rugged.
B prime
Prime period, the terrain is still a high mountain scene in a deep valley, the river began widening the role of the watershed between the rivers as a result of the increase in river terrace to minimize is the sharp ridge. River on both sides have begun to have a considerable range of the alluvial plain of the emergence of freedom of meandering rivers in the flood plain meandering flow. Than the width of the river bed meandering stream with only the width of a little wide, and at this time, river rock and fully adapt to the nature and structure of the distribution of rivers, often in rock vulnerable areas. Terrain for the whole of the current cycle could reach most of those ups and downs, hillsides and valley side slope, often the criteria for relief, rather than by the high valley at the end of the distance to the top of that. In addition, one of the original juvenile lake or waterfall, etc., to the current period has been eliminated.
C old age
Through childhood and prime erosion, the uplift of the original surface has been eroded to near sea level, and because the river will not flow to the sea with the gravity of kinetic energy to erode the ground (due to sea-level setting for the erosion datum). At this stage the valley is extremely broad, and vertical and horizontal two aspects are very gentle slope. The whole ground covered with a thick layer of debris, the debris has been weathering become very fine particles of clay or sandy soil. Significantly the development of flood plains, rivers in the broad and tortuous river flows slowly. Many times greater than the width of the valley with meandering stream. Hejian watershed as sharp as prime. Lakes, swamps and wetlands (Marshes) appear in the flood plains is not, as exists in childhood Hejian region. Due to the nature of the differences in rock, so that changes in the role of the river, in the prime of life which very significantly to the current period have been obvious. To the elderly when the final phase of the ground may have been a little plain, slightly peneplain, when the ground has been very close to the erosion datum.
D rejuvenate the role of
From childhood to old age as a cycle, because of the impact of external changes, such as rapid sea-level rise or decline sharply, so that the sudden erosion of base-level change, then the river erosion and deposition of the effect of rapid changes followed, often in prime terrain or old age, the emergence of childhood terrain characteristics. The occurrence of the phenomenon known as the Hui role, often forming the valley valley, river access, or digging meandering stream, such as cutting of the terrain.
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