Explain how a river changes its course.

A river can change its course through a process known as river meandering. This occurs when the river erodes the outer bank of a bend and deposits sediment on the inner bank, causing the bend to become more pronounced over time. As the bend becomes more pronounced, the river may eventually cut through the neck of the bend, creating a new, shorter path for the water to flow. This process can be accelerated by factors such as increased water flow, changes in sediment load, or human activities such as dam construction or channelization. Ultimately, the river will continue to meander and change its course over time as it seeks the path of least resistance.

Erosion and Deposition:

- Erosion: The river's current erodes the banks, removing soil and rock. This is most intense on the outside of bends, where water velocity is highest.
- Deposition: As the river carries sediment downstream, it deposits it on the inside of bends, where water velocity is slower. This builds up sandbars and point bars.

Meandering:

- Over time, erosion and deposition create a meandering pattern in the river's course. The bends become more pronounced as the river continues to erode and deposit material.
- Meanders occur when the river cuts into its own banks, creating a curve. The water flowing around the curve erodes the outside bank and deposits sediment on the inside bank, causing the curve to increase.

Cut-offs:

- In extreme cases, a meander can become so narrow that the river breaks through the neck of the meander and cuts a new, straighter channel.
- This occurs when the river's energy is sufficient to overcome the resistance of the bank material. Cut-offs create oxbow lakes, which are remnants of the old river channel.

Braiding:

- In some rivers, especially during floods, the river may split into multiple channels. This is called braiding.
- Braiding occurs when the river's sediment load is high and the river bed is unstable. The channels may reunite downstream, creating a braided pattern.

Other Factors:

In addition to erosion and deposition, other factors can also influence a river's course, including:

- Tectonic activity: Earthquakes, volcanic eruptions, and mountain building can uplift or subside the land, causing rivers to change their elevation and course.
- Climate change: Changes in precipitation and temperature can alter the volume and sediment load of a river, leading to changes in its course.
- Human activity: Dams, levees, and other structures can alter the natural flow of a river and permanently change its course.