Wet and warm climate is also more conducive to plant growth, which would provide more organic matter for the formation of humus. The development of a stream channel into a widening floodplain seems to follow a general, idealized aging pattern. When a stream is on a recently uplifted landmass, it has a steep gradient, a vigorous, energetic ability to erode the land, and characteristic features know as the stage of youth. Youth is characterized by a steep gradient, a V-shaped valley without a floodplain, and the presence of features that interrupt its smooth flow such as boulders in the stream bed, rapids, and waterfalls. The development of a stream channel into a widening floodplain seems to follow a general, idealized aging pattern.
Old age is marked by a very low gradient in extremely broad, gently sloping valleys.
The stream now flows slowly in broad meanders over the wide floodplain. Floods are more common in old age since the stream is carrying a full load of sediments and flows sluggishly. In general, old age characteristics are observed near the mouth of a stream where it flows into an ocean, lake, or another stream. Youthful characteristics are observed at the source, where the water collects to first form the stream channel. As the stream slowly lowers the land, the old age characteristics will move slowly but surely toward the source.