Why does gradient decrease in a river

Gradient is the slope of the stream and is measured by the difference in elevation between two points on a stream divided by the distance between the two points that the water actually flows. The steepest gradient in the long profile of a river is found in the upper course near to the source.

A high gradient indicates a steep slope and rapid flow of water i. Gradient is usually expressed in feet per mile or meters per kilometer. Originally Answered: What is a gradient of a river?

Less commonly seen are straight streams, in which channels remain nearly straight, naturally due to a linear zone of weakness in the underlying rock. Straight channels can also be man-made, in an effort at flood control.

The fastest water traveling in a meandering stream travels from outside bend to outside bend. This greater velocity and turbulence lead to more erosion on the outside bend, forming a featured called a cut bank.

Erosion on this bank is offset by deposition on the opposite bank of the stream, where slower moving water allows sediment to settle out.

These deposits are called point bars. As meanders become more complicated, or sinuous, they may cut off a meander, discarding the meander to become a crescent-shaped oxbow lake. Check out Figure 5. The following factors contribute to the widening of a river downstream.

The volume of water increases downstream due to increasing inlets from tributaries and rainwater. The flow downstream is characteristically turbulent, chaotic, and erratic. The larger discharge requires a bigger space due to the added volume of water. To contain the water, the river enlarges along the banks, leading to an enlarged width.

As a river flows downstream, its velocity increases. The speed increases due to the fact that more water is added from tributaries along the course of the river. Additionally, less water is in contact with the river bed, which results in less energy needed overcome friction. The larger mass of water causes wider and deeper water channels in order to allow water in the river to flow more freely.

The slope of a river decreases as it flows progressively downstream. Gravitational force is stronger uphill, but gentle in the lower course. Near the source, a river flows over steep slopes with uneven surfaces. It often flows over a series of waterfalls and rapids.

As a river flows down steep slopes, the water performs vertical erosion. This form of erosion cuts down towards the river bed and carves out steep-sided V-shaped valleys.