We often see and read about different landscape on the Earth, but we never thought how the flow of water can dominate the erosional process in shaping the Earth's landforms. Streams and rivers are not merely systems for moving surface water to the world's oceans and seas, but in reality they are sculptors of the land.
In other words- When a piece of the Earth’s crust first emerges from the sea and the rain begins to fall on it, the water running off begins to erode it. As the first gullies developed into channels, the drainage of this new land gets organized by the interplay of three principal factors: differential erosion, stream capture, and base level.
What is base level?
A stream of water stops flowing when it reaches the lowest level is called base level. In hydrology and geomorphology, the term base level is the limit below which flow of water cannot erode. In other words, the stream of water cannot cut deeper than its base level; therefore, its energy goes into cutting its banks sideways. As a result, the stream meanders, gradually widening its valley. For example- If river drained its water to the sea, then its base level is sea level. If lake enters a river, then the river level acts as a temporary base level for all the parts of the lake.
Types of base level
There are two types of base level- ultimate base level and local base level. The ultimate base level is sea level where the majority of water stream loses their mightiness. The local base level at which the river can erode its bed locally.
What is base level erosion?
A base level erosion is an imaginary surface of irregular shape, inclined toward the lower end of the principal, or trunk, the stream of a basin, under which the stream and its tributaries were presumed to be unable to erode. It is more applied to the critical plane of erosion, represented approximately by sea level on the coasts, which would be the lowest point toward which running water would usually erode.
How base level affects the erosion?
The stream of water cannot cut deeper than its base level; therefore, its energy goes into cutting its banks sideways, which resulted the stream meanders, gradually widening its valley. Now just imagine, if this erosion process continued long enough, then the land would be reduced to sea level.