A valley is a low area between hills or mountains.
Erosion by rivers also creates landforms called valleys. A valley is a low area between hills or mountains. Valleys have different shapes. The shape of a valley depends on how the river erodes the land over which it flows.
In the upper course of a river, the gradient of the land is very steep. Thus, the river has sufficient energy to erode the rocks in its path and cut deep into the channel, causing vertical erosion to occur. As a result, V-Shaped, narrow and steep sided valleys are formed.
In the middle course of a river, the gradient of the land is not as steep as in the upper course. Therefore, the river flows with lessn. As a result, the sides of the valley in the middle course tend to be wider than in the upper course.
In the lower course of energy and cuts less deeply into its channel. Lateral erosion occurs more than vertical erosioa river, the valleys are exceptionally wide compared to upper and middle course because the gradient of the land is gentle. As a result, lateral erosion rather than vertical erosion occurs. This gives rise to a broad flat-floored valley.